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Oceanography

THE OFFICIAL MAGAZINE OF THE OCEANOGRAPHY SOCIETY

VOL. 38, NO. 2, JUNE 2025

Video of a thin black smoker chimney spire, part of the Godzilla/Bambi complex in the northern part of the

High Rise Vent Field on Endeavour Ridge, Northeast Pacific Ocean. Jump to page 10 to read the full article

by Mihály et al. Video courtesy of Ocean Networks Canada

June 2025 | Oceanography

10

40

24

36

3 QUARTERDECK. What Do Cuts to US Science Mean for Oceanography

By E.S. Kappel

5 PERSPECTIVE. Setting a Course for Research on Offshore Wind

Development Impacts Near Nantucket Shoals

By G. Gawarkiewicz

7 PERSPECTIVE. Zooplankton and Offshore Wind: Drifters in a Sea

of Uncertainty

By G.K. Saba

10 FEATURE ARTICLE. Scientific Research and Marine Protected

Area Monitoring Using a Deep-Sea Observatory: The Endeavour

Hydrothermal Vents

By S.F. Mihály, F.C. De Leo, E. Minicola, L. Muzi, M. Heesemann, K. Moran,

and J. Hutchinson

24 FEATURE ARTICLE. How Do Tides Affect Underwater Acoustic Propagation?

A Collaborative Approach to Improve Internal Wave Modeling at Basin to

Global Scales

By M.C. Schönau, L. Hiron, J. Ragland, K.J. Raja, J. Skitka, M.S. Solano, X. Xu,

B.K. Arbic, M.C. Buijsman, E.P. Chassignet, E. Coelho, R.W. Helber, W. Peria, J.F. Shriver,

J.E. Summers, K.L. Verlinden, and A.J. Wallcraft

36 FEATURE ARTICLE. From Wind to Whales: Potential Hydrodynamic Impacts

of Offshore Wind Energy on Nantucket Shoals Regional Ecology

By E.E. Hofmann, J.R. Carpenter, Q.J. Chen, J.T. Kohut, R.L. Merrick, E.L. Meyer-Gutbrod,

D.P. Nowacek, K. Raghukumar, N.R. Record, and K. Oskvig

40 FEATURE ARTICLE. Overview of the Atlantic Deepwater Ecosystem

Observatory Network

By J.L. Miksis-Olds, M.A. Ainslie, H.B. Blair, T. Butkiewicz, E.L. Hazen, K.D. Heaney,

A.P. Lyons, B.S. Martin, and J.D. Warren

52 FEATURE ARTICLE. Exploring Climate Change, Geopolitics, Marine

Archeology, and Ecology in the Arctic Ocean Through Wood-Boring Bivalves

By J. Berge, T. Bakken, K. Heggland, J.-A. Sneli, Ø. Ødegård, M. Ingulstad, T. Thun,

and G. Johnsen

contents VOL. 38, NO. 2, JUNE 2025

June 2025 | Oceanography

Oceanography | Vol. 38, No. 2

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58 MEETING REPORT. Community Recommendations on Belonging,

Accessibility, Justice, Equity, Diversity, and Inclusion Initiatives in Ocean

Sciences: A Town Hall Discussion

By J.T. Middleton, S. Clem, K.L. Gallagher, E. Meyer-Gutbrod, A.A. Sefah-Twerefour,

M.H. Serres, M. Behl, and J. Pierson

66 DIY OCEANOGRAPHY. The PIXIE: A Low-Cost, Open-Source, Multichannel

In Situ Fluorometer Applied To Dye-Tracing in Halifax Harbor

By K. Park, D. Atamanchuk, A. MacNeil, and V. Sieben

73 OCEAN EDUCATION. Hands-On Post-Calibration of In Vivo Fluorescence

Using Open Access Data: A Guided Journey from Fluorescence to

Phytoplankton Biomass

By P. Marrec, A. Herbst, S.E. Beaulieu, and S. Menden-Deuer

83 THE OCEANOGRAPHY CLASSROOM. TAP: Teaching Analysis Poll for

Student Feedback

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86 BOOK REVIEW. A Philosophical View of the Ocean and Humanity, Second

Edition, by Anders Omstedt

Reviewed by E. Coleman

88 CAREER PROFILES. Lilian (Lica) Krug, Scientific Coordinator, Partnership

for Observation of the Global Ocean • Flávia M. Guebert, Director, Coral

Vivo Project

66

73

ON THE COVER

A thin black smoker chimney spire,

part of the Godzilla/Bambi complex in

the northern part of the High Rise Vent

Field on Endeavour Ridge, Northeast

Pacific Ocean. Video courtesy of

Ocean Networks Canada

Oceanography | Vol. 38, No. 2

June 2025 | Oceanography

A lot has already been published about the how the current and

anticipated steep reductions in US federal funding for science,

along with reductions in staffing at federal agencies, will affect

the scientific enterprise, though not all the collateral damage has

been picked up in news stories nor assessed (e.g., Flannery, 2025;

Garisto, 2025; Harvey, 2025; Wadman, 2025). From my perch,

as editor of Oceanography, I’ve been thinking about what fed­

eral funding cuts might mean for scientific publishing, and for

this journal in particular. For decades, US federal agency sup­

port has been vital to the long-term health of Oceanography

and our ability to openly share critical research on a wide vari­

ety of ocean science related topics. Many special issues and indi­

vidual articles have been used as a basis for undergraduate and

graduate classroom instruction and discussions as well as to

inform policymakers.

Federal support has also enabled us to publish two special

issues on Women in Oceanography and more recently a special

issue on Building Diversity, Equity, and Inclusion in the Ocean

Sciences. Three federal agencies supported this year’s special

issue on A Vision for Capacity Sharing in the Ocean Sciences.

These landmark special issues are contributing in various ways

to inspiring the careers of our next generation of ocean scientists,

who are vital to the continued health of our field. Importantly,

special issue sponsorship means that no authors pay publication

fees, allowing scientists from under-resourced nations or others

who may not have large research grants to fully participate. This

sponsorship also enabled The Oceanography Society (TOS), the

publisher of Oceanography and a nonprofit organization, to pro­

vide full open access to articles long before it was fashionable, or

even required, for scientific journals.

From the beginning, Oceanography’s mission has been to

communicate across disciplines in the ocean sciences—a dif­

ferent but complementary objective from other, more techni­

cal journals in our field. The aspiration is that special issues and

individual articles that are accessible to all ocean scientists, and

contributed by the global community, may spur new collabora­

tions or provide new insights that will advance the field. While

Oceanography will continue to pursue its mission by publish­

ing special issues as the situation permits, there will likely be

fewer in the future unless sponsorship opportunities with other

US-based organizations as well as groups outside of the United

States arise. Instead, we will publish more “regular” (unspon­

sored) issues that are based on unsolicited manuscripts (e.g., this

June 2025 issue; see also the September 2024 issue).

I highly encourage TOS members to check out our Author

Guidelines for instructions on how to submit a manuscript

to Oceanography and to share those guidelines with your col­

leagues. If you are unsure whether a topic might be of interest to

us, please contact one of the associate editors and discuss your

idea. Your articles, whether published in a regular or special

issue, are vital to communication among ocean scientists and

the continued health of Oceanography.

WHAT DO CUTS TO US SCIENCE

MEAN FOR OCEANOGRAPHY?

Ellen S. Kappel, Editor

REFERENCES

Flannery, M.E. 2025. “Scientific Research is Getting Cut—And That Should Scare All Americans.” neaToday, March 5, 2025, https://www.nea.org/nea-today/all-news-articles/

scientific-research-getting-cut-and-should-scare-all-americans.

Garisto, D. 2025. “Trump Moves To Slash NSF: Why Are the Proposed Budget Cuts So Big?” Nature, June 5, 2025, https://doi.org/10.1038/d41586-025-01749-x.

Harvey, C., 2025. “Trump Takes a Giant ‘Wrecking Ball’ to US Research.” E&E News, February 18, 2025, https://www.eenews.net/articles/trump-​takes-​giant-​wrecking-​

ball-​to-​us-​research/.

Wadman, M. 2025. “National Academies, Staggering From Trump Cuts, on Brink of Dramatic Downsizing.” Science, June 2, 2025, https://doi.org/10.1126/science.z4wjf7q.

ARTICLE DOI. https://doi.org/10.5670/oceanog.2025.313

QUARTERDECK

Oceanography | Vol. 38, No. 2

September 2024 | Oceanography

The Oceanography Society was founded in 1988 to advance

oceanographic research, technology, and education, and

to disseminate knowledge of oceanography and its appli­

cation through research and education. TOS promotes

the broad understanding of oceanography, facilitates con­

sensus building across all the disciplines of the field, and

informs the public about ocean research, innovative tech­

nology, and educational opportunities throughout the spec­

trum of oceanographic inquiry.

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OCEAN DATA SCIENCE: Jeremy Werdell

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Oceanography contains peer-reviewed articles that chronicle

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June 2025 | Oceanography

PERSPECTIVE

The National Academies Consensus Study Report, Potential

Hydrodynamic Impacts of Offshore Wind Energy on Nantucket

Shoals Regional Ecology: An Evaluation from Wind to Whales

(NASEM, 2024), is important, timely, and succinct. During this

time of political and financial uncertainty regarding the devel­

opment of offshore wind, this report, summarized by Hofmann

et al. (2025, in this issue), offers clear directions for the research

needed to resolve significant scientific and engineering questions

during a time of rapid change in the Northwest Atlantic Ocean.

The report highlights the difficulty of unraveling the impacts

of offshore wind development from oceanographic variabil­

ity. The Northwest Atlantic is one of the most rapidly warm­

ing regions in the world ocean (e.g., Pershing et al., 2015; Chen

et al., 2020; Seidov et al., 2021), resulting in a trend of increas­

ing stratification in the region (Harden et  al., 2020). While

there is a longer-term warming trend, in part relating to vari­

ability upstream (e.g.,  Gonçalves Neto et  al., 2021), extreme

events, such as marine heatwaves in the region, have resulted

in large temperature anomalies over time periods from days

to months. Further complicating the matter, the spatial scales

of the marine heatwaves depend on whether they result from

atmospheric forcing or ocean advection (e.g., Chen et al., 2014;

Großelindemann et al., 2022).

Another factor that makes attributing impacts in the region

complex is the manner in which Gulf Stream variability has influ­

enced continental shelf stratification and water mass properties

via increases in shelf break exchange processes. Gulf Stream

meanders have increased in peak-to-trough size, and their first

downstream appearance from the Cape Hatteras destabilization

point first shifted west over an extended period of time (Andres,

2016) and then shifted eastward over the last several years

(Sánchez-Roman et al., 2024). This increased Gulf Stream vari­

ability is likely related to a regime shift in the annual formation

rate of warm core rings in the year 2000 (Gangopadhyay et al.,

2019). An indication of the growing influence of Gulf Stream

rings and water masses on the continental shelf in this region

is the remarkable increase in frequency of mid-depth salinity

maximum intrusions (Gawarkiewicz et al., 2022). These intru­

sions commonly occur in proximity to warm core rings (Silver

et al., 2023) and bring warm salty water tens of kilometers shore­

ward of the shelf break and potentially into the offshore wind

lease areas off Nantucket Shoals. Significantly for northern right

whale prey fields, salinity profiles reveal there may be several dif­

ferent intrusions at different depths in the water column over the

continental shelf, thus possibly diminishing the concentration

within an individual intrusion layer.

The flow around offshore wind turbines is affected by pre-​

existing continental shelf processes and in turn alters those pro­

cesses. A key contribution of the Consensus Study Report is to

clearly delineate the three major scales over which the effects

on hydrodynamics must be considered and assessed: the indi­

vidual turbine scale, the wind farm scale including all turbines

in the region, and the larger regional scale over which the wind

farm scale exerts an impact via advection and changes in stratifi­

cation. This delineation is important as both the computational

approaches and the observational tools differ among the differ­

ent spatial scales. Prioritization is important, as is the linkage in

understanding among the scales.

A key portion of the report is the careful evaluation and sum­

mary of numerical modeling studies that highlight the wide

uncertainties regarding the impacts of turbine wakes on strati­

fication. Most of these studies have been directed toward infra­

structure in the North Sea, which exhibits considerable dif­

ferences in stratification, tidal velocities, and wind forcing

relative to the Nantucket Shoals region. Validation of mod­

els with careful observations is stressed and will be crucial to

reducing uncertainties.

Several challenges inhibit progress over these three spatial

scales. Large Eddy Simulations are needed at the individual tur­

bine scale to parameterize mixing and the downstream evo­

lution of turbulent wakes from the turbines. On larger scales,

much of the small-scale turbulence will need to be parameter­

ized. Progress in this specific area has been achieved by numer­

ical modelers in Europe, and parallel efforts are needed for the

Nantucket Shoals region.

A significant gap that is not addressed directly in the report is

the manner in which internal waves and tides have been chang­

ing over the past decade as stratification has changed. In addition

SETTING A COURSE

FOR RESEARCH ON OFFSHORE WIND DEVELOPMENT

IMPACTS NEAR NANTUCKET SHOALS

By Glen Gawarkiewicz

Oceanography | Vol. 38, No. 2

to ambient mesoscale and submesoscale processes, the charac­

teristics of the high frequency processes have likely changed

even in the absence of the wind farms. Again, it will be a chal­

lenge to differentiate changes resulting from the offshore wind

development and those that may have occurred as a result of

changing ocean currents and stratification. There is a clear need

for observations focused on high frequency processes to support

the numerical modeling.

All of the knowledge generated in understanding hydro­

dynamic effects will also need to be applied to further under­

standing regional marine ecology, as the prey fields, including

prey aggregation, and the roles of convergences and localized

upwelling in generating observed prey concentrations must be

better understood.

There are many challenges ahead, but the Consensus Study

Report produced by this NASEM committee is the clearest state­

ment possible of the path forward. This is particularly import­

ant, as the varied funding entities include federal agencies, off­

shore wind developers, and foundations for all of which this

report provides clear guidance on research needs and directions.

Given the dire need for alternative energy sources, there is an

urgent need for progress. The committee should be commended

for producing a clear, eminently readable report with strong rec­

ommendations. Let us hope that the resources become available

to meet the challenges that they so eloquently describe.

REFERENCES

Andres, M. 2016. On the recent destabilization of the Gulf Stream path down­

stream of Cape Hatteras. Geophysical Research Letters 43(18):9,836–9,842,

https://doi.org/​10.1002/2016GL069966.

Chen, K., G.G. Gawarkiewicz, S.J. Lentz, and J.M. Bane. 2014. Diagnosing the

warming of the Northeastern US Coastal Ocean in 2012: A linkage between the

atmospheric jet stream variability and ocean response. Journal of Geophysical

Research: Oceans 119(1):218–227, https://doi.org/10.1002/2013JC009393.

Chen, Z., Y.O. Kwon, K. Chen, P. Fratantoni, G. Gawarkiewicz, and T.M. Joyce.

2020. Long-term SST variability on the Northwest Atlantic continental shelf and

slope. Geophysical Research Letters 47(1):e2019GL085455, https://doi.org/​

10.1029/2019GL085455.

Gangopadhyay, A., G. Gawarkiewicz, E.N.S. Silva, M. Monim, and J. Clark. 2019. An

observed regime shift in the formation of warm core rings from the Gulf Stream.

Scientific Reports 9(1):12319, https://doi.org/10.1038/s41598-019-48661-9.

Gawarkiewicz, G., P. Fratantoni, F. Bahr, and A. Ellertson. 2022. Increasing fre­

quency of mid depth salinity maximum intrusions in the Middle Atlantic Bight.

Journal of Geophysical Research: Oceans 127:e2021JC018233, https://doi.org/​

10.1029/2021JC018233.

Gonçalves Neto, A., J.A. Langan, and J.B. Palter. 2021. Changes in the Gulf Stream

preceded rapid warming of the Northwest Atlantic Shelf. Communications Earth

& Environment 2(1):74, https://doi.org/10.1038/s43247-021-00143-5.

Großelindemann, H., S. Ryan, C.C. Ummenhofer, T. Martin, and A. Biastoch. 2022.

Marine heatwaves and their depth structures on the northeast US continental

shelf. Frontiers in Climate 4:857937, https://doi.org/10.3389/fclim.2022.857937.

Harden, B.E., G.G. Gawarkiewicz, and M. Infante. 2020. Trends in physical proper­

ties at the southern New England shelf break. Journal of Geophysical Research:

Oceans 125(2):e2019JC015784, https://doi.org/10.1029/2019JC015784.

Hofmann, E.E., J.R. Carpenter, Q.J. Chen, J.T. Kohut, R.L. Merrick, E.L. Meyer-

Gutbrod, D.P. Nowacek, K. Raghukumar, N.R. Record, and K. Oskvig. 2025. From

wind to whales: Potential hydrodynamic impacts of offshore wind energy on

Nantucket Shoals regional ecology. Oceanography 38(2):36–39, https://doi.org/​

10.5670/​oceanog.2025.304.

NASEM (National Academies of Sciences, Engineering, and Medicine). 2024.

Potential Hydrodynamic Impacts of Offshore Wind Energy on Nantucket Shoals

Regional Ecology: An Evaluation from Wind to Whales. The National Academies

Press, Washington, DC, https://doi.org/10.17226/27154.

Pershing, A.J., M.A. Alexander, C.M. Hernandez, L.A. Kerr, A. Le Bris, K.E. Mills,

J.A. Nye, N.R. Record, H.A. Scannell, J.D. Scott, and G.D. Sherwood. 2015. Slow

adaptation in the face of rapid warming leads to collapse of the Gulf of Maine

cod fishery. Science 350(6262):809–812, https://doi.org/10.1126/science.aac9819.

Sánchez-Román, A., F. Gues, R. Bourdalle-Badie, M.I. Pujol, A. Pascual, and

M. Drévillon. 2024. Changes in the Gulf Stream path over the last 3 decades.

In Copernicus Ocean State Report, 8th ed. K. von Schuckmann, L. Moreira,

M. Grégoire, M. Marcos, J. Staneva, P. Brasseur, G. Garric, P. Lionello,

J. Karstensen, and G. Neukermans, eds, Copernicus Publications, 4-osr8,

https://doi.org/​10.5194/sp-4-osr8-4-2024.

Seidov, D., A. Mishonov, and R. Parsons. 2021. Recent warming and

decadal variability of Gulf of Maine and Slope Water. Limnology and

Oceanography 66(9):3,472–3,488, https://doi.org/10.1002/lno.11892.

Silver, A., A. Gangopadhyay, G. Gawarkiewicz, P. Fratantoni, and J. Clark. 2023.

Increased gulf stream warm core ring formations contributes to an observed

increase in salinity maximum intrusions on the Northeast Shelf. Scientific

Reports 13(1):7538, https://doi.org/10.1038/s41598-023-34494-0.

AUTHOR

Glen Gawarkiewicz (ggawarkiewicz@whoi.edu), Woods Hole Oceanographic

Institution, Woods Hole, MA, USA.

ARTICLE CITATION

Gawarkiewicz, G. 2025. Setting a course for research on offshore wind develop­

ment impacts near Nantucket Shoals. Oceanography 38(2):5–6, https://doi.org/​

10.5670/oceanog.2025.303.

COPYRIGHT & USAGE

This is an open access article made available under the terms of the Creative

Commons Attribution 4.0 International License (https://creativecommons.org/

licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and repro­

duction in any medium or format as long as users cite the materials appropriately,

provide a link to the Creative Commons license, and indicate the changes that

were made to the original content.

June 2025 | Oceanography

ZOOPLANKTON AND OFFSHORE WIND

DRIFTERS IN A SEA OF UNCERTAINTY

By Grace K. Saba

Scientists are often tasked with addressing challenging, seem­

ingly impossible questions. An example is the recent Consensus

Study Report (NASEM, 2024a)—summarized by Hoffman

et al. (2025, in this issue)—asking: “How will potential offshore

wind-induced changes in ocean physical dynamics affect the

North Atlantic right whale in the Nantucket Shoals region?”

Most concerns about potential direct impacts of offshore wind

farms (OSW) on the North Atlantic right whale (NARW) focus

on noise interference and higher vessel activity increasing the

risk of vessel strikes. The impact of OSW on ocean physics or

hydrodynamics and subsequently NARWs is more difficult to

gauge because the effects are indirect and likely highly vari­

able. We do not yet know enough to accurately predict when

and where zooplankton will aggregate at concentrations that

support NARW foraging and success. Additionally, the under­

lying confounding challenge is how to decipher turbine-induced

hydro­dynamic changes relative to the background of extremely

high spatiotemporal variability in oceanographic conditions and

zooplankton dynamics in the Nantucket Shoals region. When

posed as a modified question—“How will potential OSW-

induced changes in ocean physical dynamics affect zooplankton

in the Nantucket Shoals region?”—a variety of scenarios come

to mind along with three questions that need to be addressed in

order to move closer to understanding whether and how OSW

may impact zooplankton.

WHAT CONTROLS ZOOPLANKTON SUPPLY AND

THE FORMATION OF AGGREGATIONS AT LEVELS

SUFFICIENT FOR NARW FEEDING?

The number of NARWs in the Nantucket Shoals region has

increased over the past decade, and although their peak for­

aging occurs during the winter and spring seasons, their pres­

ence has been observed year-round (Quintana-Rizzo et  al.,

2021). Successful NARW foraging requires an adequate sup­

ply and concentration of zooplankton (103–104 individuals m–3;

Baumgartner and Mate, 2003) as well as mechanisms that pro­

duce high-density aggregations at 100–1,000 m spatial scales

(Sorochan et  al., 2021), which coincidentally match those of

potential single turbine impacts. Coastal currents from the

Gulf of Maine and the Great South Channel control the supply

of NARWs’ primary prey, late stages of Calanus finmarchicus,

to Nantucket Shoals, while alternative copepod prey species

(Centropages spp., Pseudocalanus spp. Paracalanus spp., Oithona

similis) occur year-round with relatively different times of peak

abundance (Sorochan et al., 2021). We do not yet fully under­

stand the specific mechanism(s) that facilitate the production of

high-density zooplankton layers and aggregations in and around

Nantucket Shoals, as simultaneous NARW sightings and cope­

pod aggregations have not been observed at either tidal mixing

fronts or in a locally persistent wintertime upwelling gyre (Leiter

et  al., 2017; Sorochan et  al., 2021). The interactions between

source and advective supply, behavior (e.g., vertical migration),

ontogenetic cycles, food availability and distribution, and ocean

physical conditions that regulate these variables likely influence

zooplankton aggregation in the Nantucket Shoals region. These

dynamics are likely species-specific. Therefore, observational

studies in this region need to focus on determining which prey

species NARWs are targeting and on collecting high-​resolution

spatiotemporal observations of concurrent physical oceano­

graphic properties, copepod species distributions and aggrega­

tion dynamics, and NARW presence.

HOW MIGHT OSW AFFECT ZOOPLANKTON

ABUNDANCE AND AGGREGATION POTENTIAL?

A severe lack of observational data means that we do not know

the potential turbine-induced downstream and surrounding

increased turbulence and wake effects at scales of 0.1–1.0 km.

This could lead to, or alternate between, different scenarios of

OSW acting on zooplankton that are dependent on seasonal

ocean physical structure, circulation patterns, biological pro­

cesses, and highly variable wind, current, mixing, and tidal

dynamics. An added layer of complexity is that different zoo­

plankton species may respond differently to hydrodynamic

changes due to variable behaviors, preferred food resources,

and seasonal cycles.

Five possible scenarios are outlined here. One scenario is

that there is no overall effect; Figure 1 depicts the remaining

four. Scenario A would act to disperse surface zooplankton

aggregations and potentially those in diapause at depth (Incze

et  al., 2001). Whether this scenario could negatively change

PERSPECTIVE

Oceanography | Vol. 38, No. 2

Flow direction

Higher wind speed

Flow direction

Lower wind speed

Wind wake

Higher turbulence & ocean wake

Physical dispersion of zooplankton

(Late fall – Early spring; Unstratified)

*Seasonally

high wind

speeds

Low turbulence & ocean wake

Nutrient injection

Phytoplankton

Flow direction

Higher wind speed

Flow direction

Lower wind speed

Wind wake

Zooplankton

aggregation

Bottom-up support of zooplankton aggregation

(Late spring – Early fall; Strongly stratified)

*Seasonally

low wind

speeds

Flow direction

Higher wind speed

Flow direction

Lower wind speed

Wind wake

Higher turbulence & ocean wake

Physical dispersion of zooplankton

(Mid-spring, Mid-fall; Weakly stratified)

*Seasonally

moderate

wind speeds

Flow direction

Higher wind speed

Flow direction

Lower wind speed

Wind wake

Top-down predation on zooplankton

(All seasons)

*Seasonally

variable

wind speeds

Scenario A

Scenario B

Scenario C

Scenario D

FIGURE 1. Four potential scenarios of offshore wind turbulence and wake effects on

zooplankton in Nantucket Shoals waters.

zooplankton availability and aggregations at a level

that would impact NARW foraging is an open ques­

tion. This scenario may be of most relevance to

NARW ecology because it encompasses the time­

frame when NARW are most abundant and actively

foraging in Nantucket Shoals waters. In Scenario B,

OSW effects are strong enough to slightly disrupt

stratification, permitting nutrient injection upward

into the surface layer, but not strong enough to

break down stratification and disperse aggregat­

ing zooplankton. These higher nutrient conditions

could enhance primary production and therefore

zooplankton (Carpenter et al., 2016; Floeter et al.,

2017). Scenario C would destabilize stratification

(Carpenter et  al., 2016; Miles et  al., 2017), which

could potentially disperse zooplankton aggrega­

tions similarly to Scenario A. However, current

velocities would need to be high enough, and strat­

ification weak enough, for OSW-induced turbu­

lence to break down stratification (Carpenter et al.,

2016) and negatively impact zooplankton aggrega­

tions. Scenario D involves a more biological mecha­

nism whereby high colonization and abundances of

filter feeding invertebrates (e.g., mussels) on turbine

structures facilitate a top-down decrease in zoo­

plankton abundance (Perry and Heyman, 2020).

Although this scenario is independent of season,

different physical conditions and levels of turbu­

lence will create variable encounter rates and inter­

action times between sessile predators and zoo­

plankton prey (Prairie et al., 2012).

At the wind farm scale (10–100 km), cumula­

tive impacts of multiple turbines may act to reduce

surface current speeds and stratification and cre­

ate horizontal shear-induced upwelling and down­

welling dipoles that could differentially aggregate

or disaggregate zooplankton (Carpenter et al., 2016;

Sorochan et  al., 2021; Christiansen et  al., 2023).

Evaluating wind farm-scale impacts on oceano­

graphic and zooplankton dynamics will be more

difficult to isolate from regional high natural envi­

ronmental variability.

ARE THESE POTENTIAL OSW IMPACTS

ON ZOOPLANKTON GREATER

THAN NATURAL PROCESSES

THAT DRIVE A RANGE OF SCALES

OF SPATIOTEMPORAL VARIABILITY?

Oceanographic conditions on Nantucket Shoals

and on the broader US Northeast shelf are sub­

ject to high daily to decadal variability, driven

by local wind conditions, tidal forcing, storm

June 2025 | Oceanography

activity, and fluctuations in large-scale circulation (summa­

rized in NASEM, 2024a). Furthermore, increased frequency

of mid-water salt intrusions into shelf waters has been associ­

ated with recent warming, an inshore movement of the shelf-

break front, and changes in water column structure (Harden

et  al., 2020; Gawarkiewicz et  al., 2022). Zooplankton abun­

dance and distribution follow similar trends of variability, lead­

ing to spatiotemporal fluctuations in NARW foraging habitat,

including warming-associated declines in C. finmarchicus and

Pseudocalanus spp. (Record et al., 2019).

Given the significant uncertainty outlined here, the initial

question really should be how do we determine if OSW will

affect zooplankton and NARW in the Nantucket Shoals region?

Luckily, as Hoffman et al. (2025, in this issue) indicate, the com­

munity now has some guidance through the recently released

workshop proceedings, Nantucket Shoals Wind Farm Field

Monitoring Program (NASEM, 2024b). Isolating OSW impacts

from natural variability will require monitoring and model­

ing studies designed to target specific impacts at relevant scales

with sufficient resolution. Localized field efforts should sam­

ple along a gradient inside and outside OSW fields or include

“control” areas outside of OSW areas, before, during, and

after construction. Monitoring should also include simultane­

ous physical and biological observations at both the turbine

and wind farm area scale as well as repetition during variable

oceanographic conditions.

REFERENCES

Baumgartner, M.F., and B.R. Mate. 2003. Summertime foraging ecology of

North Atlantic right whales. Marine Ecology Progress Series 264:123–135,

https://doi.org/​10.3354/meps264123.

Carpenter, J.R., L. Merckelbach, U. Callies, S. Clark, L. Gaslikova, and B. Baschek.

2016. Potential impacts of offshore wind farms on North Sea stratification.

PLoS ONE 11(8):e0160830, https://doi.org/10.1371/journal.pone.0160830.

Christiansen, N., J.R. Carpenter, U. Daewel, N. Suzuki, and C. Schrum. 2023. The

large-scale impact of anthropogenic mixing by offshore wind turbine foundations

in the shallow North Sea. Frontiers in Marine Science 10:1178330, https://doi.org/​

10.3389/fmars.2023.1178330.

Floeter, J., J.E.E. van Beusekom, D. Auch, U. Callies, J. Carpenter, T. Dudeck,

S. Eberle, A. Eckhardt, D. Gloe, K. Hänselmann, and others. 2017. Pelagic effects

of offshore wind farm foundations in the stratified North Sea. Progress in

Oceanography 156:154–173, https://doi.org/10.1016/j.pocean.2017.07.003.

Gawarkiewicz, G., P. Fratantoni, F. Bahr, and A. Ellertson. 2022. Increasing fre­

quency of mid-depth salinity maximum intrusions in the Middle Atlantic Bight.

Journal of Geophysical Research: Oceans 127(7):e2021JC018233, https://doi.org/​

10.1029/2021JC018233.

Harden, B., G.G. Gawarkiewicz, and M. Infante. 2020. Trends in physical proper­

ties at the southern New England shelf break. Journal of Geophysical Research:

Oceans 125(2):e2019JC015784, https://doi.org/10.1029/2019JC015784.

Hofmann, E.E., J.R. Carpenter, Q.J. Chen, J.T. Kohut, R.L. Merrick, E.L. Meyer-

Gutbrod, D.P. Nowacek, K. Raghukumar, N.R. Record, and K. Oskvig. 2025. From

wind to whales: Potential hydrodynamic impacts of offshore wind energy on

Nantucket Shoals regional ecology. Oceanography 38(2):36–39, https://doi.org/​

10.5670/​oceanog.2025.304.

Incze, L.S., D. Hebert, N. Wolff, N. Oakey, and D. Dye. 2001. Changes in copepod

distributions associated with increased turbulence from wind stress. Marine

Ecology Progress Series 213:229–240, https://doi.org/10.3354/meps213229.

Leiter, S.M., K.M. Stone, J.L. Thompson, C.M. Accardo, B.C. Wikgren, M.A. Zani,

T. Cole, R.D. Kenney, C.A. Mayo, and S.D. Kraus. 2017. North Atlantic

right whale Eubalaena glacialis occurrence in offshore wind energy

areas near Massachusetts and Rhode Island, USA. Endangered Species

Research 34:45–59, https://doi.org/10.3354/esr00827.

Miles, J., T. Martin, and L. Goddard. 2017. Current and wave effects around wind­

farm monopile foundations. Coastal Engineering 121:167–178, https://doi.org/​

10.1016/​j.coastaleng.2017.01.003.

NASEM (National Academies of Science, Engineering, and Medicine). 2024a.

Potential Hydrodynamic Impacts of Offshore Wind Development on Nantucket

Region Ecology: An Evaluation from Wind to Whales. The National Academies

Press, Washington DC, 120 pp., https://doi.org/10.17226/27154.

NASEM. 2024b. Nantucket Shoals Wind Farm Field Monitoring Program.

The National Academies Press, Washington, DC, 64 pp., https://doi.org/​

10.17226/28021.

Perry, R.L., and W.D. Heyman. 2020. Considerations for offshore wind

energy development effects on fish and fisheries in the United States:

A review of existing studies, new efforts, and opportunities for innovation.

Oceanography 33(4):28–37, https://doi.org/10.5670/oceanog.2020.403.

Prairie, J.C., K.R. Sutherland, K.J. Nickols, and A.M. Kaltenberg. 2012.

Biophysical interactions in the plankton: A cross-scale review. Limnology

and Oceanography: Fluids and Environments 2(1):121–145, https://doi.org/​

10.1215/21573689-1964713.

Quintana-Rizzo, E., S. Leiter, T.V.N. Cole, M.N. Hagbloom, A.R. Knowlton,

P. Nagelkirk, O. O’Brien, C.B. Khan, A.G. Henry, P.A. Duley, and others. 2021.

Residency, demographics, and movement patterns of North Atlantic right whales

Eubalaena glacialis in an offshore wind energy development area in southern

New England, USA. Endangered Species Research 45:251–268, https://doi.org/​

10.3354/esr01137.

Record, N.R., J.A. Runge, D.E. Pendleton, W.M. Balch, K.T.A. Davies, A.J. Pershing,

C.L. Johnson, K. Stamieszkin, R. Ji, Z. Feng, and others. 2019. Rapid climate-​

driven circulation changes threaten conservation of endangered North

Atlantic right whales. Oceanography 32(2):162–169, https://doi.org/10.5670/

oceanog.2019.201.

Sorochan, K.A., S. Plourde, M.F. Baumgartner, and C.L. Johnson. 2021. Availability,

supply, and aggregation of prey (Calanus spp.) in foraging areas of the

North Atlantic right whale (Eubalaena glacialis). ICES Journal of Marine

Science 78(10):3,498–3,520, https://doi.org/10.1093/icesjms/fsab200.

AUTHOR

Grace K. Saba (saba@marine.rutgers.edu), Department of Marine and Coastal

Sciences and Center for Ocean Observing Leadership, Rutgers University,

New Brunswick, NJ, USA.

ARTICLE CITATION

Saba, G.K. 2025. Zooplankton and offshore wind: Drifters in a sea of uncertainty.

Oceanography 38(2):7–9, https://doi.org/10.5670/oceanog.2025.302.

COPYRIGHT & USAGE

This is an open access article made available under the terms of the Creative

Commons Attribution 4.0 International License (https://creativecommons.org/

licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and repro­

duction in any medium or format as long as users cite the materials appropriately,

provide a link to the Creative Commons license, and indicate the changes that

were made to the original content.

Oceanography | Vol. 38, No. 2

10

SCIENTIFIC RESEARCH AND

MARINE PROTECTED AREA MONITORING

USING A DEEP-SEA OBSERVATORY

THE ENDEAVOUR HYDROTHERMAL VENTS

By Steven F. Mihály, Fabio C. De Leo, Ella Minicola, Lanfranco Muzi, Martin Heesemann, Kate Moran, and Jesse Hutchinson

FEATURE ARTICLE

The cabled TEMPO-Mini ecological observatory module at

Main Endeavour Field. Image credit: Ocean Networks Canada

and Canadian Scientific Submersible Facility – Remotely

Operated Platform for Ocean Sciences (CSSF–ROPOS)

Oceanography | Vol. 38, No. 2

10

June 2025 | Oceanography

11

INTRODUCTION

Marine protected areas (MPAs) are designated regions set aside

to manage conservation efforts, with the primary aim of pre­

serving and protecting marine life. Effective conservation con­

siders the overall ecosystem functions, encompassing the physi­

cal, geological, and geochemical aspects of the habitat, and their

relationships with biological communities, as well as the func­

tional relationship among the ecosystems within the MPA and

the neighboring undesignated marine areas (e.g.,  Hays et  al.,

2020). Preservation efforts also extend to the cultural signifi­

cance of the marine area and the sustainable use of its resources

(Gomez et al., 2021).

Managing an MPA involves balancing multiple—often com­

peting—concerns, such as habitat protection and sustainable

use. Effective management must be informed by a strong sci­

entific understanding of an evolving ecosystem, which requires

continuous collection of key observations. For MPAs situated

in the deep sea, this can be facilitated remotely through sensors

delivering time-series observations and recurrent collection of

physical samples that help to interpret the continuous sensor

data. However, the impacts on the protected area from sensor

deployment and data collection as well as of recurring scientific

and maintenance expeditions also need to be considered in the

MPA management plan (e.g., Cuvelier et al., 2022).

In 1984, the human-occupied vehicle Alvin confirmed the

existence of “unusually large” sulfide structures and biological

communities supported by hydrothermal venting off the west

coast of Canada (Tivey and Delaney, 1986). These structures and

communities were localized to the Endeavour Segment of the

Juan de Fuca Ridge within Canada’s exclusive economic zone.

Upon discovery, and with its fortuitous proximity to coastal

ports, the Endeavour Segment became a mecca for scientific

research, enabling the dissemination of what some describe as

its magical nature and broad recognition in Canadian society of

Endeavour’s unique features and their environmental and socio­

economic significance (Tunnicliffe and Thomson, 1999).

Although the size of hydrothermal vent fields is relatively small

globally, their ecological significance is high; and even though

they are generally located in the remote deep sea, they are threat­

ened by human disturbance (Van Dover, 2012). The process of

hydrothermal venting concentrates minerals at the discharge

sites, making them ideal candidates for deep-sea mining. The

scientific interest they generate can also raise threats of overzeal­

ous sampling and other disturbances (Turner et al., 2019).

As a signatory to the Convention on Biological Diversity

(1993), Canada resolved to protect 30% of its oceans by 2030.

In 2003, Canada began this process by establishing the 97 km2

Endeavour Hydrothermal Vents (EHV) MPA as Canada’s first

MPA and the world’s first protected hydrothermal vent site

(Figure 1). Established under Canada’s Oceans Act, the primary

conservation objectives were to ensure that human activities in

the area contributed “to the conservation, protection, and under­

standing of the natural diversity, productivity, and dynamism of

ABSTRACT. Designating marine protected areas (MPAs) is an increasingly utilized policy instrument for preserving marine eco­

systems and biological diversity while also allowing for sustainable use. However, designation is only the first step and cannot

be successful without monitoring mechanisms to drive an effective and adaptive management plan. This article discusses the use

of the NEPTUNE real-time seafloor observatory—originally designed to understand the complex interdisciplinary nature of the

Endeavour mid-ocean ridge spreading center—as a tool to inform MPA management. We describe the ways in which geophysical

and geological forces control biological habitat and water column biogeochemistry, and highlight research enabled by the observa­

tory that increased our understanding of Endeavour’s hydrothermal vent ecology and these dynamic processes. Endeavour is natu­

rally undergoing change, so an understanding of the multidisciplinary mechanisms and factors controlling its environment provides

key management information.

FIGURE 1. The boundaries (white-lined box) and the five main active vent

clusters (shaded boxes) of the Endeavour Marine Protected Area are

delineated here on a bathymetric map. Coordinate system: WGS 1984

UTM Zone 9N. Image credit: Ocean Networks Canada

Oceanography | Vol. 38, No. 2

12

the ecosystem” and that these activities were “managed appro­

priately such that impacts remained less significant than natural

perturbations” (Fisheries and Oceans Canada, 2010).

The EHV MPA is on the Endeavour Segment of the Juan de

Fuca Ridge, a section of the global mid-ocean ridge (MOR) sys­

tem located in the Northeast Pacific Ocean off the west coast

of British Columbia. The MOR extends for 70,000 km through­

out the global ocean and is where tectonic plates diverge and

new oceanic crust is formed. This spreading process results

in a permeable seafloor, allowing cold seawater to percolate

downward where it is heated by rising magma from the upper

mantle. During its subseafloor circulation, the seawater reacts

chemically with the surrounding crust and is eventually ejected

back into the ocean as mineral-laden, oxygen-depleted, and

superheated fluid. The process of mixing with cold, oxygen­

ated seawater leads to a succession of rapid chemical reactions,

which form precipitates and creates the chimney-like hydrother­

mal vents that are the hallmark of the Segment (Figure 2). As the

buoyant vent plume rises, the hot metal- and sulfide-rich hydro­

thermal vent fluid continually reacts with the seawater to cre­

ate dark, smoke-like, emissions highly enriched in Fe, S, Cu, Ca,

and Zn (Feely et al., 1987). The plume rises 200–300 m above the

seafloor, at which point it reaches a neutrally buoyant state and

spreads with the local oceanic currents as the chemical processes

continue (Coogan et al., 2017). This flux of vent fluids plays a

major role in maintaining the ocean’s chemical balance. Nearer

to the seafloor, chemosynthesis-based biological communities

utilize both the energy exchange occurring when these chemical

species mix with the oxygenated seawater and the chemical spe­

cies themselves to form the basis of the hydrothermal vent eco­

systems on the seafloor and in the water column (Van Dover,

2000; Burd and Thomson, 2015).

This paper provides an overview of the main geological, bio­

geochemical, and physical processes at the Endeavour Segment

and their roles in regulating the biological communities and

habitat structures that host ecosystems at the vents and near the

seafloor. We describe highlights of the past 16 years of scien­

tific research and monitoring enabled by the NEPTUNE sea­

floor cabled observatory that support management decisions for

the MPA. Recently, the EHV MPA’s boundaries were repealed

and subsumed into the 133,017 km² Tang.ɢ̱ wan – ḥačxʷiqak –

Tsig̱ is (TḥT) MPA. This significantly expanded area is of cul­

tural and economic significance to coastal Indigenous peoples

of the west coast of North America and is cooperatively man­

aged by the Council of the Haida Nation, the Nuu-chah-nulth

Tribal Council, the Pacheedaht First Nation, and the Quatsino

First Nation, together with Fisheries and Oceans Canada

(Government of Canada, 2024).

THE NEPTUNE OBSERVATORY

In addition to its designation as an MPA, the Endeavour Segment

was also selected as one of the three Integrated Studies Sites for

the US National Science Foundation-funded Ridge 2000 pro­

gram (Fornari et al., 2012) that attracted significant global sci­

entific attention. Highlighting Endeavour’s scientific value, the

proposal for a NEPTUNE cabled observatory was successfully

funded, with the primary purposes to understand the spread­

ing, subduction, and faulting of the Juan de Fuca plate, as well as

the ecosystems and oceanography off the west coast of Canada.

For the purposes of MPA management, the deep-sea observa­

tory enhances observation and monitoring in the area.

FIGURE 2. This close-up view shows a black smoker chimney at the Main

Endeavour Field. Image credit: ONC and CSSF–ROPOS

June 2025 | Oceanography

13

Operated by Ocean Networks Canada (ONC), the NEPTUNE

observatory comprises an 840 km fiber-optic cable extend­

ing from Vancouver Island across the North American and

Juan de Fuca tectonic plates to connect five major node sites

to power and the internet (Barnes et al., 2007). The western­

most Endeavour node supports the scientific sensors in the

heavily instrumented Endeavour Hydrothermal Vents MPA

(Table 1, Figures 3 and 4). Real-time data, archived data, and

data products from sensors in the axial valley and on the flanks

of the Endeavour Segment of the Juan de Fuca Ridge have been

available since 2010 through ONC’s digital infrastructure,

Oceans 3.0 (Owens et al., 2022). Regular expeditions using ships

and remotely operated vehicles (ROVs) to maintain infrastruc­

ture also collect observations and physical samples to ground

truth and complement the sensor data. Internet connectivity

from the ships allows the Canadian and international science

community to participate from shore to conduct experiments

and sampling strategies to aid in developing a more complete

understanding of the physical, geological, and biological pro­

cesses of this protected environment (Table 1).

TABLE 1. Summary of major disciplines, sensor technology, and geological, physical, chemical, and biological properties monitored and their scientific

and MPA monitoring impacts. MEF = Main Endeavour Field. RCM = Regional Circulation Mooring North and South.

MONITORING

EQUIPMENT

PROPERTIES

MEASURED

VENT FIELD/

SITES

(See Figure 3)

SIGNIFICANCE

(Value in MPA management)

KEY PUBLICATIONS

DISCIPLINE: GEOPHYSICS AND GEOCHEMISTRY

1. Seismometers and

accelerometers

Seismic ground

motions and

low-frequency

hydroacoustic signals

• RCM-N

• MEF

• Mothra

• Ridge Flank

• Node

Identify periods of seismic unrest driven by

tectonic spreading events that are linked

to changes in venting and/or eruptions.

Also, detect chimney collapses and activity

from baleen whales.

• Krauss et al., 2023

• Bohnenstiehl et al., 2004

• Smith and Barclay, 2023

2. Bottom pressure

recorders (BPR)

Vertical seafloor

movements and sea

level changes

• RCM-N

• MEF

• Ridge Flank

• RCM-S

• Node

• Mothra

Inflation/deflation can indicate changes

in the underlying magma chamber that

affects the hydrothermal system and can

precede spreading events.

• Barreyre and Sohn, 2016

3. Benthic and

Resistivity Sensors

(BARS), paired with

vent fluid samples

Temperature,

resistivity, and redox

potential

• MEF

• Mothra

Changes in chemical composition of

vent fluids over time, and the influence

of chemical and heat fluxes on the

composition and diversity of benthic vent

biological communities.

• Xu et al., 2017a

4. Vent imaging sonar

3D vent plume and

heat flux mapping

• MEF

Hydrothermal heat and chemical flux

variability is a fundamental control on the

ecosystem.

• Bemis et al., 2015

• Xu et al., 2014, 2017b

5. Serial gas tight

sampler

Fluid geochemistry

• MEF

Changes in chemical composition of vent

fluids over time, and the influence of

chemical and heat fluxes on the makeup

and diversity of benthic vent biological

communities.

• Seyfried et al., 2022

• Evans et al., 2023

6. Water samplers

(RAS-PPS)

Water geochemistry

and biology

• MEF

Diffuse venting and its effects on the

benthic ecosystem.

• Lelièvre et al., 2017

7. Sediment traps

Particulates from

vent plumes

• MEF

• West Flank

• South Axial

Hydrothermal venting and its effects on

the water column.

• Coogan et al., 2017

• Mills et al., 2024

• Beaupre-Olsen et al., 2025

DISCIPLINE: PHYSICAL OCEANOGRAPHY

1. Regional Circulation

Moorings

Ocean circulation

and water properties

(temperature, salinity,

and density)

• RCM-N

• NW Mooring

• RCM-S

• SW Mooring

Proxy measurement of the overall heat flux

variability to the ocean from hydrothermal

venting. Current circulation in and above

the axial valley controlling larval and vent

plume chemistry dispersal.

• Thomson et al., 2003

• Xu et al. 2014, 2017b

2. Conductivity,

temperature, and

depth (CTD)

Temperature, salinity

and density, dissolved

oxygen

• Node

Near seafloor water properties.

Continued on next page…

Oceanography | Vol. 38, No. 2

14

GEOLOGY AND SEAFLOOR HABITAT

The Endeavour MPA hosts hydrothermal vent ecosystems

whose formation and persistence are directly linked to the

dynamic geological and tectonic processes of the Juan de

Fuca Ridge. Understanding this interplay through continu­

ous, multidisciplinary monitoring is foundational to effective

MPA management.

The Endeavour Segment is an intermediate-rate spreading

center (full rate: ~52 mm yr–1) (DeMets et al., 2010; Krauss et al.,

2023) characterized by a 10 km long and 1 km wide axial val­

ley flanked by rift crests rising 100–150 m above the valley floor.

Extensive and vigorous hydrothermal venting occurs within the

axial valley focused at five main active vent clusters spaced about

2–3 km apart (Figure 1; Kelley et al., 2012). The Main Endeavour

(MEF) and Mothra fields have received significant scientific

attention and are currently being monitored by sensors con­

nected to the NEPTUNE observatory. The High Rise and Salty

Dawg fields (see Figure 1) are designated for minimally intru­

sive studies and outreach opportunities (Fisheries and Oceans

Canada, 2010) and have no cabled sensors.

The uniqueness of hydrothermal venting regions, with respect

to other deep-sea benthic habitats, stems from the chemical flux

and exchange of heat between the ocean and the seafloor and

the geologically rapid change of the seafloor morphology due

to local tectonic dynamics. This leads to a chemically and phys­

ically extreme environment that hosts the specialized life that

has physiologically and biologically adapted to the geologically

controlled environment. Although vent ecosystems are rare and

their global extent is small, their contribution to the understand­

ing of life and their ecosystem functions and services are sig­

nificant and are considered ideal candidates for designation as

Vulnerable Marine Ecosystems and recommended for Area-

Based Management Tools (e.g., Menini and Van Dover, 2019).

The Endeavour Segment features a combination of active and

inactive chimneys, edifices, and mounds along its axial valley.

The active structures cluster into the five major vent fields with

more than 400 inactive structures as well as the diffuse venting

sites interspersed among them. Conceptually, they are geolog­

ically connected, and the entire ridge segment can be consid­

ered a single temporally and spatially varying vent field driven

MONITORING

EQUIPMENT

PROPERTIES

MEASURED

VENT FIELD/

SITES

(See Figure 3)

SIGNIFICANCE

(Value in MPA management)

KEY PUBLICATIONS

DISCIPLINE: BIOLOGY

1. Video cameras

Video, paired with

other sensors

(i.e., temperature)

• MEF

• Mothra

Track biological community structure and

responses to venting physico-chemistry

dynamics.

• Cuvelier et al., 2014, 2017

• Lelièvre et al., 2017

• Carter, 2025

• Robert et al., 2012

• Lee et al., 2015

2. Biological samples

Whole specimens,

tissue, assemblages

and e-DNA

• High Rise

• MEF

• Mothra

Characterization of vent and vent-

periphery communities (from microbes to

megafauna).

• Perez and Juniper, 2016, 2017

• Perez et al., 2023

• Lelièvre et al., 2018

• Georgieva et al., 2020

3. Colonization

experiments

Community

recolonization/

ecological succession

• MEF

Investigate faunal colonization (from

microbes to macrobenthos) simulating

recovery from natural perturbations

(e.g., eruptions).

• Ongoing studies

4. Passive larval

trap collectors

Benthic invertebrate

larvae

• MEF

Larval ecology and genetic connectivity

among different vent, vent periphery,

and background deep-sea benthic

communities.

• Ongoing study

5. ROV video

surveys, including

photogrammetry

Habitat and benthic

community dynamics

• MEF

• Mothra

• High Rise

Track, at larger spatial scales, temporal

changes of vent community composition

and responses to natural perturbations.

• Neufeld et al., 2022

DISCIPLINE: SOUNDSCAPES

1. Cabled hydrophone

arrays

Intensity and direction

of broadband sound

• MEF

Vent activity monitoring, earthquake

detection (near and distal), marine-mammal

detection and monitoring.

• Smith and Barclay, 2023

2. Deep acoustic

lander (autonomous,

Dalhousie University)

Sound velocity,

pressure, conductivity,

temperature, salinity;

intensity and direction

of broadband sound

• MEF

Water-column properties affecting sound

propagation, vent activity monitoring.

• Smith and Barclay, 2023

TABLE 1. Continued…

June 2025 | Oceanography

15

by heat from a continuous axial magma chamber (Jamieson and

Gartman, 2020). Over at least the last 2,000 years, there have

been no large-scale eruptions with significant lava flows that

could bury these vent fields (Jamieson et al., 2013; Clague et al.,

2014, 2020). Krauss et al. (2023) attribute this to the degassing

of the axial magma chamber, which limits extrusive magmatism

and results in the mature chimneys, edifices, and mounds, both

active and inactive, that define the Segment. Concurrently, the

underlying shallow magma chamber ensures sufficient heat and

chemical flux to sustain regular hydrothermal circulation and

consistent sulfide structure growth.

Long, continuous time series of physical parameters provide

opportunities to reveal complex dynamics and ongoing evolu­

tion of the vent system. For example, Barreyre and Sohn (2016)

correlated vent fluid temperatures with bottom pressure fluc­

tuations and estimated the permeability of the shallow upflow

zones near hydrothermal venting using poroelasticity theory.

The study revealed that the Main Endeavour Field (MEF) pos­

sesses geospatially distinct shallow upflow zones characterized

by different effective permeabilities, which sets it apart from

Lucky Strike and the East Pacific Rise, sites with different geo­

logical characteristics and spreading rates.

At Smoke and Mirrors, located near the southern Benthic and

Resistivity Sensors (BARS; shown in the MEF inset in Figure 3),

Barreyre and Sohn (2016) modeled higher effective permea­

bilities characteristic of a slow spreading center, such as Lucky

Strike, with lower heat flux and a thicker extrusive layer that has

ample permeable pathways. Just 150 m apart at Grotto (located

near the northern BARS shown in the MEF inset in Figure 3),

they modeled higher effective permeabilities that are character­

istic of a fast spreading center, such as the East Pacific Rise, with

higher heat flux and a thinner extrusive layer more frequently

paved by volcanic activity.

Rather than attributing these differences to spreading rate, the

effective permeability likely varies due to output from the irreg­

ular distribution of the underlying magma body. This is corrob­

orated by anecdotal visual evidence from repeated visits show­

ing the southern part of the MEF waning in black smoker output

(e.g.,  Smoke and Mirrors edifice), while the northern part of

the field (Grotto edifice) is growing and gaining in vigor. These

results and visual observations also imply that the magma sup­

ply within intermediate spreading centers can vary in space and

time (possibly rapidly) and therefore regionally modify the ben­

thic environment to host biological communities that are more

suited to fast or slow spreading centers.

Continuous geophysical monitoring, primarily using cabled

seismometers and bottom pressure recorders (BPRs, Table 1),

tracks the tectonic activity that can drive these changes in the

FIGURE 3. ONC infrastructure within the area of the Endeavour vent fields and adjacent ridge flanks. The node (orange square) powers the instru­

ment platforms (white circles) that host scientific sensors connected to the internet via fiber-optic cables (white lines). Moorings—both autonomous and

cabled—are shown as yellow circles. Image credit: ONC

Oceanography | Vol. 38, No. 2

16

environment. The real-time data streams permit continuous

monitoring of seismic events and seafloor deformation, pro­

viding insights into processes influencing environmental sta­

bility and enabling timely responses to significant events. Since

2018, heightened seismicity has been observed by Krauss et al.

(2023), mirroring precursors to past diking events (1999–2005).

This culminated in a notable increase in activity in March 2024,

including an M4.1 earthquake and periods with up to 200 events

per hour, suggesting the segment may be approaching the next

diking event, prompting the scientific community to meet in

November 2024 to prepare for a rapid response to a major per­

turbation of the system.

Understanding the chemical environment driving these eco­

systems is critical. Due to the harsh environment of hydrother­

mal venting regions, geochemical sensors for measuring the

continuous temporal variability of the chemistry of fluid emis­

sions are very limited, and scientific research has relied predom­

inantly on laboratory analysis of discrete samples obtained on

scientific expeditions. To obtain a continuous time series at high

temperature vents, ONC employed a cable-connected BARS

to measure temperature, resistivity, and redox potential (eH)

of the vent fluids in situ (Table 1). With discrete samples taken

at the beginning of the deployment and at the time of recov­

ery, the continuous time series of the sensors’ measurements are

used to infer changes in fluid chemistry. However, these sensors

reside in black smoker vents with 300°–350°C fluid emission

and often do not last a full year between maintenance expedi­

tions. Another method to improve time resolution of the vari­

ability of chemical fluxes is to remotely collect discrete sam­

ples. Currently, a serial gas tight sampler is deployed alongside a

BARS. Its containers can be remotely triggered to collect a time

series of 12 vent fluid samples (Seyfried et al., 2022). The timing

of the sampling is adapted to changes in seismicity or vent fluid

temperatures, allowing correlation between specific geological

events and vent fluid chemistry.

The current period of heightened seismicity marks a critical

phase for the evolution of the Endeavour Segment. It presents a

rare opportunity to observe a potential dike intrusion or spread­

ing event that would offer valuable data for refining models of

mid-ocean ridge processes. Studying the Endeavour Segment,

with its intermediate spreading rate characteristics, provides a

key comparison point between fast- and slow-spreading sys­

tems across the globe and other intermediate spreading cen­

ters (e.g., the Galápagos Spreading Center). An impending tec­

tonic event may cause significant shifts in hydrothermal output

(heat and chemistry), providing a natural experiment to study

the resilience and adaptive responses of the specialized vent

communities within the MPA. To better capture such an event,

Dalhousie University and the University of Washington, in part­

nership with ONC, enhanced observatory capabilities by deploy­

ing five autonomous ocean bottom seismometers in summer

2024; an additional 20 ocean bottom seismometers (including

replacements for the 2024 units) are scheduled for deployment in

summer 2025. This denser network will improve detection and

location of seismicity, providing crucial data for understanding

geological and tectonic processes and their impacts on hydro­

thermal vent ecosystems. It will inform future MPA management

strategies regarding natural and anthropogenic disturbances.

OCEANIC ENVIRONMENT

Changes in and redistribution of heat and chemical fluxes from

the vent fields along Endeavour’s axial valley alter seafloor char­

acteristics, affecting benthic ecosystems as well as the overlying

water column and the pelagic ecosystem it hosts. Not only is

the seawater chemistry directly altered, but changes in the heat

flux from hydrothermal venting affects the local ocean circula­

tion through changes in buoyancy input from the rising hydro­

thermal plumes. On an axial valley scale, the rising plume gen­

erates inflow near the seafloor toward the hydrothermal vents,

which facilitates the retention of vent field larvae and plankton.

Conversely, the rising plume can also entrain planktonic organ­

isms, moving them up into the water column where along-axis

currents can relocate them to vent sites with more retentive cir­

culation, or higher up in the water column where they can be

swept away by ambient ocean currents to less hospitable ocean

environments (Thomson et al., 2003). If the organisms have the

ability to swim vertically or alter their buoyancy, they can use

this circulation to move to a preferred location. There is obser­

vational evidence of larvae exhibiting this type of behavior at

other vents sites (Mullineaux et al., 2013). On the segment scale,

the off-axis propagation of the plume alters the chemistry of the

ocean (Coogan et al., 2017; Beaupre-Olsen et al., 2025) and has

a marked impact on the overlying pelagic ecosystem, enhancing

secondary productivity (Burd and Thomson, 2015).

Estimating the flux of hydrothermal fluid and heat along the

Endeavour Segment has generally been conducted by observing

water property anomalies, either by dense shipborne or autono­

mous underwater vehicle (AUV) sampling. These observations

are inverted to estimate flux using the known temperature of the

vent fluid as it leaves the seafloor (Kellogg, 2011), resulting in an

overall value of heat flux over the time window of the repeated

surveys. With yearly AUV surveys (2004, 2005, 2006), Kellogg

and McDuff (2010) identified a transient anomaly over the Salty

Dawg vent field, suggesting that there is spatial and temporal vari­

ability in hydrothermal flux; however, their temporal resolution

made it difficult to determine both the subseafloor causes and the

water column effects. As an alternative to annual AUV surveys

with their inherent coarse time resolution, four moorings of cur­

rent meters and water property sensors (CTDs) were installed in

the axial valley of the Endeavour Segment. The array is designed

to utilize the “sea breeze effect” caused by the rising buoyant

plume. This effect relates horizontal currents to the intensity of

heat flux from the hydrothermal venting (Thomson et al., 2003);

therefore, variability in hydrothermal heat flux is continuously

June 2025 | Oceanography

17

estimated in real time. This four-mooring array also monitors

the background bathymetrically modified circulation that con­

trols the mixing and dispersal of the chemical-laden hydrother­

mal plume (Xu et al., 2013; Coogan et al., 2017; Figure 3), and

enables researchers to relate circulation dynamics to ecosystem

dynamics (Cuvelier et al., 2014; Lelièvre et al., 2017).

A specialized sonar was developed to image rising plumes

in real time after researchers observed that avoidance sonar on

submersibles could detect reflections from these plumes (Bemis

et al., 2015). The deployment of the Cabled Observatory Vent

Imaging System (COVIS; Figure 4) marked a significant tech­

nological milestone. COVIS allows for direct tidal-frequency

resolution of the total flux from the multiple hot vent orifices

that makes up the rising buoyant plume. Utilizing the imagery

of the acoustic backscatter off the turbulent fluctuations of the

buoyant plume and the Doppler shift of the backscattered sig­

nal, researchers were able to estimate the rising plume veloc­

ity and the expansion rate and heat flux to the ocean from the

hydrothermal venting and its variability through time, and to

gain insights into the diffuse low temperature flow (Bemis et al.,

2012; Xu et al., 2013, 2014).

Chemical analysis of hot vent fluid samples collected by a

remotely controlled, internet-connected serial gas tight sampler

revealed details of the input of nutrient transition metals (e.g., V,

Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo) from the oceanic crust to the

water column (Evans et al., 2023). These metals play an import­

ant role in nutrient-related biological processes. They are essen­

tial for the growth of organisms and can be rapidly utilized in

near-surface waters and therefore limit growth. Determining

the dynamics of chemical flux across the seafloor interface using

these types of cabled seafloor samplers informs understanding of

the benthic-pelagic coupling that regulates the trophodynamics

over regional scales and offers insights into the global role of

hydrothermal venting in primary and secondary productivity in

the ocean (e.g., Burd and Thomson, 2015; Cathalot et al., 2021).

SOUNDSCAPE

A significant challenge when monitoring a site like Endeavour

is posed by the aggressive environment that can deteriorate

instrumentation quickly, especially when placed in the vicinity

of the plume. Passive acoustic monitoring (PAM) from hydro­

phones positioned at a safe distance from the hot and chemically

FIGURE 4. Artist’s rendering

of a selection of ONC’s cabled

and autonomous instruments

monitoring Endeavour. Image

credit: ONC

a. Regional circulation

mooring

b. Junction box

c. Bottom pressure recorder

d. Hydrophone array

e. Broadband seismometer

f. Cabled Observatory Vent

Imaging Sonar

g. Passive larval trap collector

h. Sediment trap

i. Deep Acoustic Lander

j. Remotely operated vehicle

k. Water sampler

l. TEMPO-Mini ecological

module

m. Benthic and Resistivity

Sensors

June 2025 | Oceanography

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Oceanography | Vol. 38, No. 2

18

corrosive fluids is used to monitor, in real time, the soundscape

at the site for extended periods of time. For example, PAM was

applied successfully to the detection and classification of explo­

sive events at volcanically active sites (Chadwick et al., 2008).

Different features of the sounds produced by venting are

related to the physical mechanisms producing the sounds.

These, in turn, are influenced by physical parameters such as

flow rate, chimney height, sound speed, and cavity size (Little

et al., 1990; Crone et al., 2006; Smith and Barclay, 2023). Studies

aimed at establishing the connection between these parameters

and the sounds produced can, in principle, enable the contin­

uous, remote, long-term monitoring and investigation of flow

rates, growth, and other aspects of the vents via PAM.

To explore the potential of PAM, ONC deployed a hydro­

phone at MEF in 2018, and then upgraded the installation to a

four-element array in 2023. Additionally, Dalhousie University’s

Deep Acoustic Lander (Figure 4) was deployed and recovered

in 2021 and 2023, further augmenting the time series (Smith

and Barclay, 2023). Though still in its infancy, this study has

already detected a large number of transient (i.e., of duration

measurable in seconds or less), often impulsive, sounds char­

acterizing the soundscape at MEF. These include chimney col­

lapses, waterborne signals associated with earthquakes, and a

number of other sounds whose origins are being investigated.

A recent study reports that numerous such signals were cap­

tured by ONC’s hydrophones during the major seismic event of

March 5–6, 2024. Through the investigation of power spectral

density, ambient-noise coherence, and cross-correlation with

other sensors at MEF, the same study highlighted other, longer-​

term changes in the MEF soundscape that may be associated

with changes to the venting activity resulting from the increased

seismicity in the region (Smith and Barclay, 2024).

Finally, PAM is also being explored as a tool for environmen­

tal impact assessment. Some marine organisms may use acoustic

cues to select settlement locations around hydrothermal vents

(Eggleston et al., 2016). Industrial activities, such as shipping

and deep-sea mining, can potentially interfere with the local eco­

system by introducing changes in the soundscape, even though

they may be located at significant distances (Chen et al., 2021).

Understanding of the local soundscape relevant to the biological

activity of a site is an important component of an effective envi­

ronmental impact mitigation strategy (Lin et al., 2019).

VENT BIOLOGY

Numerous biological studies utilizing video imagery and sam­

ples collected from ROVs and submersibles have been con­

ducted at Endeavour. They focused on describing the benthic

assemblages inhabiting a range of hydrothermal vent condi­

tions, from those on high-temperature black smoker chimneys

to those sustained by broadly spread diffusive flows (Sarrazin

et al., 1997; Tunnicliffe et al., 1997; Lelièvre et al., 2018; Murdock

et  al., 2021). The early studies of hydrothermal vent systems

described a specialized fauna characterized by low species diver­

sity, high biomass, and high levels of endemicity (i.e., species

only occurring at vent environments; Tunnicliffe and Fowler,

1996; reviewed in Van Dover, 2000).

A key characteristic of typical vent fauna is successful asso­

ciations between chemoautotrophic, symbiotic microorganisms

and their macroinvertebrate hosts (Lonsdale, 1977; Corliss et al.,

1979). Utilizing the chemical energy from sulfur, hydrogen,

iron, and methane, vent microorganisms fix carbon not only in

symbiont associations with host species but also as free-living

cells or in extensive bacterial mats (Dick, 2019). Host-symbiont

associations often achieve high densities and biomass surround­

ing the areas of hydrothermal fluid flow. At the Endeavour

vents, the most conspicuous and abundant vent fauna assem­

blages are comprised of the siboglinid polychaete tubeworm

Ridgeia piscesae, alvinelid polychaetes Paralvinella sulfincola

(sulfide worm) and Paralvinella palmiiformis (palm worm), the

limpet Lepetodrilus fucensis, and many other species of snails

(Figure 5a-d, Sarrazin et al., 1997). Studies to date have inven­

toried close to 60 vent-associated species at Endeavour, with

12 endemic species not occurring anywhere else in the world

(Fisheries and Oceans Canada, 2010). Sampling of macrofauna

associated with tubeworm bushes near the Grotto edifice alone

revealed up to 31 species occurring in substrate patches of less

than 0.1 m2, and it highlighted the importance of keystone

species such as R. piscesae in creating habitat complexity that

enhances local biodiversity (Lelièvre et al., 2018).

The roles of microbial diversity and production in con­

trolling large-scale nutrient elemental cycling and ecosystem

function have also been topics of studies based on the frequent

sampling at Endeavour. Samples of diffusive sulfidic vent fluids

helped to quantify microbial production pathways (denitrifica­

tion, anammox, and dissimilatory nitrate reduction to ammo­

nium), aiding global estimates of nitrogen (N) removal rates

to the subsurface biosphere that represent 2.5%–3.5% of total

marine N loss (Bourbonnais et al., 2012). Microbes were also

the focus of a number of studies examining vent fauna host-​

symbiont relationships and population structure. The tubeworm

Ridgeia piscesae, a keystone species, was found to have the same

phylotype Gammaproteobacteria symbiont (Ca. Endorifitia

persephone) as six other tubeworm species in the Eastern Pacific,

revealing high levels of interconnectivity between the Northeast

Pacific and the East Pacific Rise vents (Perez and Juniper, 2016).

However, the same authors later uncovered multiple genotypes

within E. persephone making up the symbiont assemblages

of R. piscesae and argued that this genetic diversity could be

an important predictor of resilience to environmental change

(Perez and Juniper, 2017).

Since the installation of seafloor cables and platforms in the

axial valley of the Endeavour Segment in 2010, in situ instru­

ments and sensors, including time-lapse video imagery, have

been providing new insights into the environmental controls

June 2025 | Oceanography

19

FIGURE 5. A sample of habitat heterogeneity and biological diversity of vent-associated and vent periphery fauna at Endeavour. (a,b) Black smoker

chimneys colonized by dense assemblages of R. piscesae tubeworms. (c,d) Typical assemblages that occur near diffusive hydrothermal flow, includ­

ing alvinelid polychaetes (Paralvinella sulfincola, Paralvinella palmiiformis), polynoid scale worms (Branchinotogluma tunnicliffae), limpets (Lepetodrilus

fucensis), and snails (Buccinum thermophilum). (e) Field of view of the Mothra vent field observatory camera showing the seafloor partially covered

by white bacterial mats, Ridgeia piscesae tubeworms, Buccinum thermophilum gastropods, and the deep-sea spider crab, Macroregonia macrochira.

(f) Vent periphery sulfide and (g,h) basalt structured seafloor that provide habitat for corals, sponges, and mobile macro- and megafauna. Image credits:

ONC and CSSF–ROPOS

over vent species community composition and biorhythms. At

Main Endeavour Field, a video camera platform (TEMPO-Mini;

Auffret et al., 2009), installed in collaboration with the French

national institute for ocean science and technology (IFREMER),

provided nearly 10 years of continuous data. The length of the

video time series enabled analyses that, for the first time, estab­

lished astronomical (tidal) and atmospheric (storm passages)

forcing as a control on vent macrofauna behavior (Cuvelier et al.,

2014, 2017; Lelièvre et al., 2017). The data revealed that mobile

macrofauna, such as sea spiders (pycnogonids) and polychaete

scale worms (polynoids), responded to the passage of win­

ter storms 2.2 km above by regulating their biorhythms to the

storm-​triggered cyclical oscillations in the diffusive vent flow

dynamics (Lelièvre et al., 2017). Video observations of picno­

gonids and scale worms living in association with R. piscesae

tubeworm bushes that are supported by low-temperature dif­

fuse venting also indicated that the animals respond to the cur­

rents generated by these storms. At the latitude of Endeavour,

storm-induced currents have a four-day cycle due to the pas­

sage of the storms and a 16-hour cycle resulting from the iner­

tial oscillations generated by the storm winds that can propa­

gate to the seafloor as inertial internal waves. As the currents

cyclically increase, they dilute the warm, low-oxygen vent fluids,

and the animals can be observed moving deeper into the bush,

disappearing from camera view. A study performed in waters

1,688 m deep at the EMSO-Azores Mid-Atlantic Ridge obser­

vatory (EMSO = European Multidisciplinary Seafloor and water

column Observatory) corroborates these findings, as biologi­

cal rhythms and circadian clock gene expression of the hydro­

thermal vent mussel Bathymodiolus azoricus were found to be

Oceanography | Vol. 38, No. 2

20

directly tied to tidal cycles (Mat et al., 2020). Combined, these

findings provide compelling evidence of more direct dynami­

cal influences of the surface ocean and the planetary climate on

deep ocean hydrothermal vent ecosystems than was previously

thought. Furthermore, they highlight the importance of long-

term observations supported by the NEPTUNE observatory in

detecting faunal community changes at Endeavour in response

to upper ocean climate variability.

A second seafloor camera installed at Mothra vent field in

2020 is further contributing to our understanding of the tem­

poral dynamics of highly mobile and non-vent exclusive ben­

thic megafauna, such as zoarcid and macrourid fishes and

decapod crustaceans, by employing machine learning auto­

matic classification and counting of the most abundant taxa

(Carter, 2025; Figure 5e). NEPTUNE’s multiple video cam­

era platforms, which cover a range of vent habitat types and

incorporate embedded pipelines for automated imagery pro­

cessing, can be used to inform MPA managers of long-term

trends in faunal abundance and diversity (Aguzzi et al., 2020;

Ortenzi et al., 2024).

A recent study focused on non-vent benthic megafauna

inhabiting peripheral habitats (e.g.,  Figure 5f,g) located as

much as a few kilometers away from the main active Endeavour

vent sites. ROV video surveys conducted at Main Endeavour

and High Rise vent fields revealed diverse assemblages domi­

nated by slow growing sessile animals, such as rosselid vase

sponges, alcyonacean corals, and crinoids (Neufeld et al., 2022).

A key finding was that corals were nearly absent and rosselid

sponges were found in very low abundances within 25–50 m of

active chimneys but became progressively more abundant and

diverse moving away from the vents; they occurred predomi­

nantly at bare basalt ridges and on walls of inactive sulfide chim­

neys. Species richness measured using rarefaction curves were

significantly higher at inactive chimneys but never reached

asymptotic values, demonstrating an undersampled and incom­

plete species catalogue (Neufeld et al., 2022). These results high­

light the importance of studies that consider vent-​periphery

habitats covering a wider, landscape-scale habitat heterogene­

ity in order to uncover the true ecological “sphere of influence”

(sensu Levin et  al., 2016) and the true biodiversity conserva­

tion and MPA management value surrounding any hydrother­

mal vent system. Furthermore, parallel studies at Endeavour,

such as Georgieva et al. (2020) that investigated microbiomes of

vent-periphery sponges in the genus Spinularia, uncovered puta­

tive chemosynthetic Gammaproteobacteria (Thioglobaceae and

Methylomonaceae) directly providing nutrition to the sponges,

indicating that typical non-vent megafauna still benefit from

symbiont associations deriving from dispersed vent fluids in the

surroundings of active hydrothermal sites. Given deep-sea mas­

sive sulfide deposit mining activities being proposed for inactive

vent sites around the globe (Jamieson and Gartman, 2020), the

Endeavour Segment, which is protected under the TḥT MPA,

therefore becomes a natural study and monitoring site for fur­

ther exploration of the importance of vent-periphery habitats,

biodiversity, and resilience to human impacts.

Photogrammetric mosaics produced by repeated flyovers

using remote or autonomously operated vehicles with dedicated

camera systems (Van Audenhaege et al., 2024) allow monitoring

of ecological dynamics from vent-edifice to centimeter scales.

Motion photogrammetry has been used to generate highly accu­

rate habitat terrain models, with high predictive power for faunal

assemblage distribution (Gerdes et al., 2019). The most import­

ant community structuring variables in these habitat models

are often distances to diffuse and black fluid exits, as well as the

height of the chimney complex (Gerdes et al., 2019; Girard et al.,

2020). At Endeavour, regular maintenance visits to the obser­

vatory with a scientific ROV enabled assembly of a sequence of

3D photogrammetry models from repeat visits to the Mothra

vent field. Data are being analyzed, with preliminary results pro­

viding insights into how chimney accretion and erosion affect

spatial distribution and community succession of vent fauna

(Tom Kwasnitschka, GEOMAR Helmholtz Centre for Ocean

Research Kiel, pers. comm., October 22, 2024).

Additionally, ROV survey data (video and navigation) col­

lected during observatory maintenance expeditions can be

mined to produce kernel density “heat maps” of significant eco­

system components, indicators, and stressors (Juniper et  al.,

2019). As the observatory maintenance and operations occur

on a yearly basis, these maps are continuously updated and are

used as essential MPA spatial management tools by quantita­

tively assessing research pressure on the vents (e.g., ROV tracks

and sampling efforts), hotspots of biodiversity associated with

vents (typical chemosynthetic communities), and vent periph­

ery habitats (e.g.,  corals and sponges) (Fisheries and Oceans

Canada, 2025). An interactive map is available online with mul­

tiple geographical information system (GIS) layers of all obser­

vatory maintenance activities, spatial distribution of vent­

ing habitat structures (e.g.,  active and inactive edifices), and

associated biodiversity.

CONCLUSION

Since deployment of scientific instrumentation at the Endeavour

MPA in the fall of 2010, a total of 103 peer-reviewed papers have

been published, as well as 10 dissertations and one book chap­

ter (in The Sound of Hydrothermal Vents, Smith and Barclay,

2023). Of the 103 journal articles, 51 were based directly on sen­

sor data archived in Oceans 3.0 and/or discrete samples collected

on maintenance expeditions, while 28 articles used ONC data

along with data from other sources (e.g., earthquake, acoustics).

The remaining 24 articles were either review/overview articles

or articles supported by research enabled by ONC. The internet

access and the power offered by the deep-sea observatory pro­

moted the development of new hydrothermal vent and seafloor

monitoring technology, while the research resulted in significant

June 2025 | Oceanography

21

advancement in our understanding of the geophysics, vent biol­

ogy, and oceanography of the MPA.

The observations collected by cabled sensors and during

the repeated visits for infrastructure maintenance are freely

available (unless there is a known student thesis that could be

affected by early release of the data). There is growing under­

standing of hydrothermal ecosystems’ functions, their connec­

tivity to other ecosystems, their benefit to humanity, and their

role in the ocean’s chemical balance. However, a clear picture of

the “value” of hydrothermal sites to weigh against disturbance,

for example by deep-sea mining or scientific sampling, is not

complete (Turner et al., 2019). The objective of continuous, long

time-series monitoring of vent sites by seafloor observatories is

to enable observation of natural disturbances and how succes­

sion proceeds afterwards to understand what level of anthro­

pogenic disturbance or scientific sampling might be tolerated.

In addition, real-time monitoring is essential for monitoring

episodic natural perturbations. A framework is being devel­

oped among the Canadian government and scientific institu­

tions for a rapid response to a perturbation of the hydrother­

mal system at the Endeavour Segment to gain observations of

the changes in the water column chemistry and the benthic

and pelagic ecosystems.

The Endeavour MPA is remote, 300 km offshore and in

2.2 km of water, and seemingly clear of threats that impact

coastal oceans. However, it is not isolated from ocean acidifi­

cation, microplastic pollution, hypoxia, and even storm inten­

sity. Real-time data and regular, yearly maintenance visits to

Endeavour monitor change due to natural processes, pollution,

and climate change.

With the Endeavour MPA subsumed into the much larger off­

shore TḥT MPA (Figure 6), now encompassing multiple eco­

logically or biologically significant marine areas, remote moni­

toring strategies are expected to change in accordance with new

MPA conservation and management goals. While the cabled

seafloor sensors will play a crucial role, other complementary

monitoring and infrastructure upgrades are needed to continue

increasing scientific understanding, to contribute to improved

management or conservation, and to monitor the effectiveness

of the new MPA protections.

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ACKNOWLEDGMENTS

ONC is primarily funded by the Canada Foundation for Innovation, Government

of Canada, University of Victoria, and Government of British Columbia. Thank

you to Mark Rankin for preparing Figure 1, and to Norman Coloma for Figure 4.

Many thanks to the captains and crew of R/V T.G. Thompson, CCGS John P. Tully,

and E/V Nautilus, as well as the crews of the remotely operated vehicles ROPOS,

Hercules, Odysseus, and Millennium. Finally, and most importantly, we would

like to thank all the researchers who have been fascinated by the Endeavour

Segment and provided the impetus for its designation as an MPA. In particu­

lar, we thank S.K. Juniper (in memoriam) for his passion, enthusiasm, and curi­

osity, all of which spurred a multitude of new and exciting discoveries about

Endeavour vent communities.

AUTHORS

Steven F. Mihály, Fabio C. De Leo, Ella Minicola (ellaminicola@oceannetworks.ca),

Lanfranco Muzi, Martin Heesemann, Kate Moran, and Jesse Hutchinson,

Ocean Networks Canada, Victoria, BC, Canada.

ARTICLE CITATION

Mihály, S.F., F.C. De Leo, E. Minicola, L. Muzi, M. Heesemann, K. Moran, and

J. Hutchinson. 2025. Scientific research and marine protected area moni­

toring using a deep-sea observatory: The Endeavour hydrothermal vents.

Oceanography 38(2):10–23, https://doi.org/10.5670/oceanog.2025.315.

COPYRIGHT & USAGE

This is an open access article made available under the terms of the Creative

Commons Attribution 4.0 International License (https://creativecommons.org/

licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and repro­

duction in any medium or format as long as users cite the materials appropriately,

provide a link to the Creative Commons license, and indicate the changes that

were made to the original content.

Oceanography | Vol. 38, No. 2

24

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AT BASIN TO GLOBAL SCALES

By Martha C. Schönau, Luna Hiron, John Ragland, Keshav J. Raja, Joseph Skitka, Miguel S. Solano, Xiaobiao Xu,

Brian K. Arbic, Maarten C. Buijsman, Eric P. Chassignet, Emanuel Coelho, Robert W. Helber, William Peria, Jay F. Shriver,

Jason E. Summers, Kathryn L. Verlinden, and Alan J. Wallcraft

INTRODUCTION

The underwater soundscape encompasses a range of ambi­

ent, anthropogenic, and biological sound, with research span­

ning acoustic communications to passive acoustic monitoring.

The density of water allows sound, which is a pressure wave,

to travel short distances and across ocean basins. The speed of

sound is set by water temperature and salinity, and pressure.

As it travels, sound scatters from the bathymetry, the surface,

animals, or other objects. Sound refracts when it encounters a

difference in sound speed, which can be introduced by fronts,

eddies, currents, vertical stratification, internal tides, and gravity

waves and mixing.

Soundscape modeling, such as that used to trace the impacts

of anthropogenic noise on marine mammals, is dependent on

the sound speed structure employed in the ocean model. The

vertical motions of internal tides and internal gravity waves

(IGWs) bring cold water up and push warm water down, chang­

ing the sound speed (Gill, 1982). Internal tides and IGWs dissi­

pate energy to both smaller and larger scales. The sound speed

in tidally forced simulations may differ drastically from simula­

tions without tidal forcing. Simulations are also highly sensitive

to grid spacing, mixing parameterizations, and boundary condi­

tions. Identifying the differences of tidally driven ocean models

from their non-tidal counterparts and the actual ocean, and the

length scales that resolve IGW processes, may in turn inform

how internal wave models should be used for diverse acoustic

and biological studies.

This paper presents progress in the modeling of internal tides

and IGWs, the effect of these advances on modeling sound speed

and sound propagation in underwater ray-tracing acoustic mod­

els, and the use of deep learning (DL) to predict the ocean state.

The research stems from a coordinated project funded under the

Office of Naval Research (ONR) Task Force Ocean (TFO) initia­

tive designed to train early career scientists in cross-​disciplinary

oceanography, underwater acoustics, and machine learning

techniques. The project was dubbed “TFO-HYCOM” after

the US Navy’s operational HYbrid Coordinate Ocean Model

(HYCOM), which featured prominently in the research project.

BACKGROUND AND APPROACH

Internal Gravity Waves

Internal gravity waves exist as undulations along constant den­

sity ocean surfaces (isopycnals) with a restoring force of grav­

ity. As IGWs displace isopycnals, they create a profile of depth-​

dependent velocities. Internal tides, a special type of IGWs,

exist at tidal frequencies and are generated by tidal flow over

ABSTRACT. Accurate prediction of underwater sound speed and acoustic propagation is dependent on realistic representation

of the ocean state and its underlying dynamics within ocean models. Stratified, high-resolution global ocean models that include

tidal forcing better capture the ocean state by introducing internal tides that generate higher frequency (supertidal) internal waves.

Through the disciplines of internal wave modeling, acoustics, and machine learning, we examined how internal wave energy moves

through numerical simulations, how this energy alters the ocean state and sound speed, and how machine learning could aid the

modeling of these impacts. The project used global, basin-scale, and idealized HYbrid Coordinate Ocean Model (HYCOM) simu­

lations as well as regional Massachusetts Institute of Technology general circulation model (MITgcm) simulations to examine how

tidal inclusion affects sea surface height variability, the propagation and dissipation of internal wave energy, and the sensitivity of

internal wave modeling to vertical and horizontal grid spacing. Sound speed, acoustic parameters, and modeled acoustic propaga­

tion were compared between simulations with and without tidal forcing, and deep learning algorithms were used to examine how a

tidally forced ocean state could be generated while reducing computational costs.

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bathymetric features (e.g.,  Bell, 1975). They differ from near-​

inertial IGWs that are generated by high-frequency wind forc­

ing that have frequencies near the Coriolis frequency (Pollard

and Millard, 1970). Aside from internal tides and near-inertial

waves, there is a spread of internal wave energy known as the

IGW continuum spectrum (Garrett and Munk, 1975), which

can be shaped by mesoscale eddies (Barkan et  al., 2017) and

nonlinear interactions. Nonlinear interactions can bring IGW

scales down to 1 m or less and can cause IGWs to overturn and

break, a dominant process in the mixing of the ocean interior

(MacKinnon et al., 2017).

IGWs can be discussed in terms of their vertical structures, or

“modes” (Gill, 1982). These modes approximate IGW dynamics

as a linear superposition of standing waves in the vertical direc­

tion and propagating waves in the horizontal direction. This is

reasonable in a buoyancy-driven flow where the horizontal scale

is much greater than that of the vertical. Each wave mode has

a characteristic length, phase speed, and vertical structure that

depends on the frequency of the IGW, the Coriolis frequency,

and the vertical density gradient. The lowest baroclinic mode

has a singular, two-layer horizontal structure (i.e., the veloci­

ties are out of phase above and below the thermocline); higher

modes have greater vertical structure. Waves in the IGW spec­

trum at frequencies greater than tidal frequency, called super­

tidal, are thought to arise from nonlinear interactions between

internal tides and near-inertial IGWs (Müller et al., 1986).

IGW variability has not been well captured by global ocean

simulations. Simulations may lack certain forcing (e.g.,  tidal)

or may parameterize, rather than resolve, finer-scale processes.

Barotropic tidal models, where water movement is uniform with

depth, have been available since the 1970s (e.g., Hendershott,

1981), but they do not allow stratified flow. In the last two

decades, increases in computational power have made it possi­

ble to accurately model internal tides in a stratified ocean. These

models have evolved from using horizontally uniform two-layer

(Arbic et al., 2004) or multilayer (Simmons et al., 2004) stratifi­

cation to embedding tidal forcing in ocean general circulation

simulations with stratification that varies geographically in a

realistic manner (Arbic et al., 2012).

This study focused on the modeling of internal tides and

IGWs in HYCOM, the backbone of the operational forecasting

system of the US Navy (Metzger et al., 2014). The Navy HYCOM

simulations use a hybrid vertical coordinate system: isopycnal

coordinates in the stratified ocean interior, a dynamic transi­

tion to pressure (p) coordinates in the surface mixed layer, and

bathymetry-following (σ) coordinates in shallow shelf water

(Bleck, 2002; Chassignet et al., 2006). The simulations use real­

istic atmospheric forcing from the Navy Global Environmental

Model (NAVGEM; Hogan et al., 2014) and can be run with or

without data assimilation and with or without tidal forcing.

Sophisticated methods from the data-assimilation literature

have also been applied to bring the tidal simulations closer to

observations (Ngodock et al., 2016).

For this study, HYCOM was primarily utilized without data

assimilation. Data assimilation can create “shocks” as it brings

the model closer to observations, disrupting the geostrophic

balance between horizontal pressure gradients and rotation.

Raja et al. (2024) found that as the modeled ocean tries to restore

geostrophic balance, spurious low-mode internal waves are gen­

erated. These waves have frequencies that overlap with the tidal

and inertial bands, complicating the analysis of naturally occur­

ring tidal and near-inertial waves. The interaction of these spuri­

ous IGWs with other internal waves or eddies and their eventual

dissipation can also alter the ocean energetics. For this reason,

most of our HYCOM internal tide and IGW studies (e.g., Raja

et al., 2022), and subsequent acoustics research for this project,

have used HYCOM simulations without data assimilation.

The HYCOM model was used in this study with a variety of

vertical, horizontal, and bathymetric grid spacings. The most-

used model setups were regional and global versions of tidally

forced HYCOM with a horizontal grid spacing of 1/25° to 1/50°,

typically the highest resolution spacing at which Global HYCOM

can be run. This is finer than the 1/12° grid spacing available in

most of today’s publicly available global ocean models. Idealized

versions of the model, such as using a single temperature-​

salinity profile in a two-dimensional field, were used to isolate

the effects of internal tides on stratification and energy trans­

fer. Regional simulations using the Massachusetts Institute of

Technology general circulation model (MITgcm) were com­

pared to HYCOM simulations because of MITgcm’s different

boundary conditions and, for this study, its finer grid spacing.

Sound Propagation

Internal tides and IGWs have long been associated with under­

water acoustics. The influence of internal tides and IGWs on

sound speed variability has been at the core of many observa­

tional (e.g., Flatté et al., 1979; Tang et al. 2007; Worcester et al.,

2013) and modeling (e.g.,  Colosi and Flatté, 1996) studies.

Alternatively, acoustic tomography, an inverse method that uses

long-range acoustic propagations to infer ocean structure, has

been used to study the barotropic and baroclinic tides themselves

(Dushaw, 2022). In addition to the tilt of density surfaces caused

by internal waves, temperature and salinity fluctuations along a

constant density surface, called “spice,” can have a similarly large

impact on sound speed and its gradients (Dzieciuch et al., 2004).

“Spiciness,” caused by ocean stirring by mesoscale eddies, could

differ between tidal and non-tidally forced ocean simulations.

This study focused on upper ocean acoustic structure and

propagation. In the uniform temperature and salinity layer found

at the ocean surface in many regions, pressure causes sound

speed to increase with depth, often creating a local subsurface

maximum in sound speed (Helber et  al., 2008). This subsur­

face sound-speed maximum, called the sonic layer depth (SLD),

has the potential to form a surface-layer duct where sound is

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refracted upward from the SLD and reflected downward by the

surface, allowing acoustic energy to travel long distances. The

sound speed gradient below the SLD, called the below-layer gra­

dient (BLG), can influence the potential of this surface-layer duct

to trap energy.

For this project, sound speed, its variability, the SLD, and

the BLG were compared between simulations with and with­

out tidal forcing. Acoustic transmission loss (TL), an estimate

of acoustic pressure, was calculated from a virtual source using

a three-dimensional ray-tracing acoustic model, Bellhop 3D

(Porter, 2011). TL exemplifies how the differences in sound

speed between differently forced ocean simulations can affect

acoustic propagation models.

PROGRESS IN IGW MODELING

Bringing Models Closer to Observations

Realistically capturing ocean variability at different length scales,

from large-scale eddies to smaller coastal features, is a central

goal of global ocean models. Sea surface height (SSH) variability

is a useful proxy for mesoscale ocean variability. The SSH wave­

number spectrum was used as a single descriptor of the rela­

tive strength of ocean variability as a function of length scale.

Wavenumber, defined as one divided by wavelength, is large

where spatial scales are small. Figure 1f shows an example of

the wavenumber spectra and the spectral slope of the mesoscale

variability (the steepness of the spectrum from 250 km to 70 km

wavelength). The SSH spectral slope varies greatly by location

(Figure 1e; Zhou et al., 2015). The slope is steepest (–5) along

the western boundary current (Gulf Stream), which has large-

scale currents and high mesoscale eddy variability. The slopes

are flatter (close to –3) in the mid-latitude interior, such as the

eastern North Atlantic, and much flatter (close to –1) in the

equatorial region.

The inclusion of tidal forcing in ocean models is paramount

to bringing SSH variability in simulations closer to observations.

Figure 1 compares a series of high-resolution regional 1/50°

North Atlantic HYCOM simulations to satellite altimetry obser­

vations. Without tidal forcing, high-resolution models could not

replicate this spatial SSH variability (e.g., Figure 1a,b; Chassignet

and Xu, 2017). With tidal forcing (Figure 1c,d), the SSH spec­

tral slope in the equatorial Atlantic and the eastern subtropi­

cal North Atlantic began to match observations. Here, there are

strong barotropic tides and strong stratification in the upper layer

of the water column. In these regions, SSH variability at length

scales of 70–120 km increased, flattening the spectral slope in the

70–250 km mesoscale range (Figure 1f). High-resolution bathym­

etry (Figure 1b) and high-frequency wind variability (Figure 7b

in Xu et al., 2022) had comparably minor impacts on the spec­

tral slope, except at local scales where internal tides are generated

along topography, such as near the shelf break (Xu et al., 2022).

NEATL

NEATL-T-HB

Zhou et al. (2015)

Wavenumber Spectra

NEATL-HB

NEATL-T

FIGURE 1. (a–e) Mesoscale sea surface height (SSH) wavenumber spectral slope in the

Atlantic Ocean based on a series of 1/50° numerical simulations and observations: (a) NEATL

(no tides), (b) NEATL-HB (no tides, with high-resolution bathymetry), (c) NEATL-T (with tides),

(d) NEATL-T-HB (with tides, high-resolution bathymetry), and (e) satellite observations from

Zhou et al. (2015). (f) Example of the wavenumber spectra averaged from 10°S–10°N and

35°–15ºW from observations and four model configurations. The mesoscale spectral slope

in panels a–e was calculated between 70 km and 250 km. Modified from Xu et al. (2022;

their Figures 7 and 11)

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From Global to Regional: Supertidal Energy

Tidal energy is mainly concentrated at the diurnal and semi­

diurnal astronomical forcing frequencies, and some of this

energy is transferred to higher (and lower) frequencies. Band-

pass filtering can separate the energy between that at semi­

diurnal tidal frequencies (Figure 2a) and that at higher, super­

tidal frequencies (Figure 2b). Diurnal and semidiurnal energy

dominate most of the internal tide spectrum, except along the

path of large amplitude internal tides near the equator. Most of

the research on IGW-IGW interactions in the open ocean has

focused on “subharmonic resonance,” a transfer of tidal energy

to lower frequencies (e.g., Ansong et al., 2018). For this project,

Solano et al. (2023) evaluated the decay of the low-mode inter­

nal tide due to superharmonic wave-wave interactions, leading

to the transfer of tidal energy to higher, supertidal frequencies.

Globally, supertidal kinetic energy (KE) accounts for about 5%

of the total IGW energy. Supertidal energy is greatest at low

latitudes. Equatorward of 25°, 9% of the total tidal energy is

transferred to supertidal KE. At generation sites of large ampli­

tude internal tides or “hotspots,” such as the Bay of Bengal,

the Amazon Shelf, and the Mascarene Ridge, 25%–50% of the

IGW KE is found at supertidal frequencies (Solano et al., 2023;

Buijsman et al., 2025).

Here, we focus on two regions with high supertidal KE: the

Amazon Shelf and the Mascarene Ridge (Figure 3). The nonlin­

ear IGW KE transfer from primary to supertidal frequencies has

a banding pattern (Figure 3a,b) that is also present in the hor­

izontal divergence of the supertidal energy flux (Figure 3c,d),

suggesting a common mechanism for the nonlinear energy trans­

fer between length scales. Decomposing the energy into separate

modes (Figure 3e,f), the banding pattern appears when the low­

est modes (1+2) are superimposed but not for individual modes.

FIGURE 2. Time-mean and depth-integrated internal wave

kinetic energy (J m–2) band-passed at (a) semidiurnal, and

(b) supertidal frequencies. Regions with relatively high

supertidal energy indicated by the black rectangles are:

(1) the Amazon Shelf, (2) the Mascarene Ridge, and (3) the

Luzon Strait. (c) Zonal mean (averaged over seafloor depths

>2,000 m and 10° latitude bins) of the maximum number of

modes (vertical structures) resolved for various internal tide

frequency resolution criteria. K1, M2, M4 represent the domi­

nant diurnal, semidiurnal, and supertidal constituents of inter­

nal tides with decreasing wavelengths, respectively. For the

horizontal (vertical) resolution, the dark-colored polygons

(dashed lines) mark the range of the number of resolved

modes for the zonal mean, and the light-colored polygons

±1 standard deviation from this mean.

Zonal mean of the maximum

number of modes resolved

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Thus, it is likely that the mode-1 and mode-2 internal tides inter­

fere constructively at the locations of the patches where their

velocities are in phase and increase the tidal amplitude, steepen

the internal tide, and enhance the energy transfer to higher har­

monics. The locations of these patches are modulated by the

slowly varying subtidal current and the spring-neap cycle, with

greater energy available to transfer to higher-​harmonics during

spring tides (Solano et al., 2023).

Impacts of Horizontal and Vertical Grid Spacing

on IGWs in Global Models

Ocean model grid spacing, both horizontal and vertical, deter­

mines how bathymetry and the wavelengths of IGW modes are

resolved. For example, a decrease in HYCOM horizontal grid size

from 8 km to 4 km can increase the IGW generation and energy

density by about 50%, largely because it increases the number of

internal wave modes resolved (Buijsman et al., 2020).

We examined what diurnal, semidiurnal, and supertidal ver­

tical wave modes could be resolved in a global, 1/25° tidally

forced global HYCOM simulation with 41 layers (Figure 2c).

Horizontal spacing and IGW wavelengths vary spatially in global

ocean models. Earth’s sphericity causes grid spacing to decrease

poleward, while wavelengths of tidally generated IGWs increase

poleward with the increase of the Coriolis frequency (Buijsman

et al., 2025). We used the criterion that a vertical mode could be

resolved if there were at least six to eight horizontal grid spac­

ings per wavelength (Stewart et al., 2017). A similar criterion was

applied for the vertical resolution, called vertical criterion CZA.

However, this criterion was designed for z-coordinate models,

whereas HYCOM is an isopycnal model below the mixed layer.

Therefore, an additional criterion was developed to account for

the changes in vertical and horizontal velocity structure caused

by isopycnals, called vertical criterion CZB.

In the horizontal, internal wave modes with lower frequen­

cies (longer wavelength) were better resolved. For example, K1

had eight modes resolved at the equator and 20 modes near the

K1 turning latitude of about 30° (Figure 2c). (Poleward of this

latitude, the tidal frequency is lower than the Coriolis frequency,

and diurnal IGWs cannot exist.) The shorter wavelength, M2,

had fewer modes resolved, with only about four modes resolved

at the equator. For supertidal waves, M4, which has the most

energy globally (Buijsman et al., 2025), only two modes were

resolved. The number of resolved modes was sensitive to the ver­

tical resolution criteria. CZB appeared to be a more appropriate

FIGURE 3. At the Amazon Shelf and the Mascarene Ridge: (a,b) time-mean and depth-integrated kinetic energy transfer (‹Π(τ=9hr)›); (c,d) time-mean,

depth-integrated divergence of supertidal energy flux ( ∙‹FHH›); (e,f) time-mean surface kinetic energy (KE) for the superposition of modes 1 and 2.

Panels (a–f) were modified from Solano et al. (2023). (g) Mean sound speed and (h) standard deviation of sound speed for each the tidally and non-tid­

ally forced HYCOM simulations from May 20–29, 2019, in the Amazon region, plotted by latitude along the dotted line shown in (a). The star and radial

(dashed black line) in (a) are noted for reference in Figure 6. In (b), a short, dashed line indicates the transect used in Figure 5b,c.

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criterion than CZA. Accounting for the isopycnal layering in

HYCOM, as in CZB, a maximum of 12 diurnal modes could be

resolved at the equator.

Vertical Grid Spacing in Idealized Models

Recent discussions among the oceanography community

resolve that global models can achieve a more accurate ocean

state if they include tidal forcing and have a horizontal grid spac­

ing on the order of 1/50° or finer (the most up-to-date global

HYCOM has 1/25° grid spacing). However, the optimal num­

ber of vertical layers needed in submesoscale resolving mod­

els to resolve internal tides and their energetics is unknown.

To explore this question, we used an idealized HYCOM con­

figuration with 1/100° horizontal grid spacing (~1 km), forced

only by the semidiurnal (M2) tides over a centrally spaced

ridge, and varied the number of layers in the simulations from

8 to 128 (Figure 4; Hiron et al., 2025). The idealized configu­

ration allowed the problem to be isolated from contamination

by ocean eddies and currents while resolving all the physics

allowed in HYCOM.

Each idealized simulation was initialized with a climatologi­

cal temperature profile averaged over the Cape Verde area and

constant salinity. The domain size, approximately 8,000 km in

the zonal direction, was large enough to prevent the reflection

of internal tides at the boundaries. The vertical grid discretiza­

tion was chosen based on characteristic wavelengths of differ­

ent IGW modes. To generate internal tides, a steep ridge with a

Gaussian shape was added in the center of the domain. The crit­

icality of the slope, which is a measure of the ridge steepness

normalized by the ray slope of the internal waves, was larger

than one, allowing for nonlinear waves and wave beams to be

generated (Garrett and Kunze, 2007).

The wave beams were the strongest near the ridge (Figure 4a).

The depth-integrated vertical KE of the 8- and 16-layer sim­

ulations differed from the others in amplitude and phase

(Figure 4b). As the number of layers increased, the simulations

became more similar. For the 48- to the 128-layer simulations,

amplitude and phase were similar across simulations. When

integrated from 0–2,000 km, the tidal barotropic-to-baroclinic

energy conversion, the vertical kinetic energy, and the turbu­

lent dissipation were greatest in the 128-layer simulation and

decreased with coarser vertical grid spacing (Hiron et al., 2025).

These variables converged for the simulations with greater than

48 layers, showing that the number of vertical layers can deter­

mine the IGW energy transfer; however, these results may differ

at other horizontal grid spacings.

A Final Word on Grid Spacing: Interaction of

IGWs and Eddies

The IGW spectrum covers the transfer of energy between IGWs

and the transfer of KE from its injection at large scales in eddies,

near-inertial waves, and tides to the smallest scales. It is applica­

ble globally but uses free parameters to account for regional and

seasonal variations of the ocean state, such as the slowly varying

background circulation and surface forcing. Ongoing research

focuses on what determines these parameters and any devia­

tion from this spectral form; nonlinear interactions involving

IGWs, such as those on display in the Amazon basin and near

Mascarene Ridge, are thought to be of particular importance.

Previous work on IGW-IGW interactions has identified

some important processes that move energy to smaller scales

(McComas and Bretherton, 1977; Dematteis et al., 2022). These

FIGURE 4. (a) Snapshot of the vertical velocity for the 128-layer simulation, zoomed in to the ridge centered at 40°W, where the domain is symmetric

about the ridge. The black triangles indicate the location of the sound speed profiles in (c,d). (b) Time-averaged, depth-integrated vertical kinetic energy

(½ ∫w2dz), where w is the vertical velocity, for different vertical discretization: 8, 16, 32, 48, 64, 96, and 128 layers. (c) Mean and (d) standard deviation

of sound speed 83 km from the ridge for the 8-, 16-, 32-, 48-, and 96-layer simulations.

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studies considered IGW-IGW interactions to be the dominant

processes. One mechanism, called “induced diffusion,” involves

the interaction of near-inertial and tidal IGWs. Induced diffu­

sion is thought to be very important in transferring KE across

length scales. However, most studies have not considered

IGW-eddy interactions in the same manner.

Skitka et al. (2024) used a framework to diagnose IGW-eddy

interactions with IGW-IGW interactions in a regional MITgcm

(1/48°) ocean simulation of the North Pacific. They found that

IGW-eddy interactions induce a downscale KE flux in a man­

ner analogous to IGW-IGW interactions. At this grid spacing,

the “eddy-induced diffusion” was the dominant mechanism of

energy exchange within the IGW supertidal continuum, and

comparable to the wave-induced diffusion achieved by regional

models with 250 m (1/192°) horizontal grid spacing. Thus, finer

vertical and horizontal grid spacing is expected to change the

details of the IGW cascade in simulations, including the mecha­

nisms and rate of energy transfer and its dissipation.

ACOUSTICS

Tidally Forced Simulations and Sound Speed

We first examined how tidal forcing affects sound speed and

acoustic properties using a series of global HYCOM (1/25°)

simulations with or without tidal (T) forcing and with or with­

out data assimilation (DA), four simulations in all. Each simu­

lation was forced by wind and had 41 layers. Hourly output was

recorded from May to June 2019. Temperature and salinity were

interpolated from the native grid to a uniform 2 m vertical grid

and then used to compute sound speed.

As an initial comparison, the sound speed variability in each

of the four simulations was compared to glider observations

over a small geographic area in the North Pacific (Figure 5a;

Rudnick, 2016). A mean and standard deviation of sound speed

was computed from May 20 to May 26, using three-hour out­

put from the simulation and averaged over the region covered

by the glider track. The glider profiled from the surface to 500 m

depth roughly every three hours. Although this is not a region

of large tidal energy, the simulations with tidal forcing still had

FIGURE 5. (a) Standard deviation of sound speed for May 20–26, 2019, from Global HYCOM simulations with and without tides and with and without

data assimilation (DA) at the location indicated on the map off the coast of California. Simulations were compared to standard deviation computed from

glider observations over the same week and location. (b,c) The depth of the 1,510 m s–1 sound speed along 20°N, extending from the coast of Hainan

Island eastward (111.16°E–160°E) for global HYCOM simulations. Bathymetry is overlaid on each, with the Luzon Strait located at 1,000 km distance from

the coast. (d,e) SLD and BLG for global HYCOM simulation with tides (Exp 19.0) and for a nonhydrostatic regional MITgcm simulation at the Mascarene

Ridge near the island of Madagascar (see Figure 3b).

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greater sound speed variability. A simulation with tidal forcing

undulates the thermocline leading to greater temperature and

salinity (and thus sound speed) variability at a given depth. Data

assimilation brought the simulations closer to observations;

however, it can also abruptly alter the temperature and salin­

ity during an assimilation window, causing implausible jumps

in sound speed. The elevated sound speed variability in the DA

simulations could be caused by natural ocean variability or this

“shock.” For these reasons, and those discussed in the earlier sec­

tion, Internal Gravity Waves, we chose to use ocean simulations

without DA while studying the sensitivity of acoustics to IGWs.

Acoustic Case Studies at IGW Hotspots

At IGW hotspots, such as the Luzon Strait, the Amazon Shelf,

and the Mascarene Ridge, tidal forcing strongly undulates the

upper ocean, and there is IGW energy transfer among modes

(see the section, From Global to Regional: Supertidal Energy).

Across the Luzon Strait, we compared the depth variability of

a single sound speed surface between the tidally forced and

non-tidally forced global HYCOM simulations (Figure 5b,c). In

the tidally forced simulation, depth striations radiated from the

Luzon Ridge, located at 1,000 km distance, and other ridges with

steep topography (e.g., 4,800 km) as tides propagated in both

directions (Figure 5b). These were largely absent in the simula­

tion without tides (Figure 5c).

We hypothesized that such differences in sound speed between

the tidal and non-tidally forced simulations would cause notable

differences in acoustic propagation. To test this idea, we turned

to the Amazon region, where semidiurnal internal tides propa­

gate northeastward away from the coast (Figure 3). The mean

sound speed along the transect was similar between the tides

and no-tides simulations (Figure 3g), but they differed in sound

speed variability (Figure 3h). The tidal simulation had peri­

odic “banding” in sound speed variability in the thermocline

(~150 m depth) at locations near where there was greater IGW

energy transfer (Figure 3a).

A 1,500 Hz virtual acoustic source was placed at 20 m depth

at 4.1°N, 44.8°W, a location of enhanced sound speed variabil­

ity and IGW energy transfer (yellow star in Figure 3a). The

sound speed, vertical sound speed gradient, and transmission

loss were examined along the 30° radial (clockwise from north).

In the tidal case, there were undulations in sound speed and

SLD (Figure 6a). Without tidal forcing, the sound speed was

more uniform, and SLD was deeper. A deeper SLD will also

typically improve transmission in the surface layer. Tidal forc­

ing also introduced changes to vertical sound speed gradients

(Figure 6a,b) and can be inferred to introduce them in the hori­

zontal as well. Surface layer transmission occurred in both cases

but was stronger in the simulation without tidal forcing. Turning

to time series (Figure 6c), TL tended to be greater in simulations

with tidal forcing than without and often fluctuated at semidiur­

nal timescales (i.e., every 12 hours), such as from May 20 to 23.

The semidiurnal variability extended to both SLD and BLG. In

the nontidal case, TL varied with eddies and currents but not at

semidiurnal frequencies (Figure 6c).

Because the horizontal and vertical structures of the sound

speed determine the path of the sound, the introduction of ver­

tical and horizontal gradients in sound speed in the simulation

with tides could have resulted in more scattering and refraction

of sound throughout the waveguide. However, the mesoscale

differences between the tidal and non-tidal simulations made it

difficult to directly compare their acoustic properties. Some of

the simulation variability was caused by tidal interaction with

the mesoscale field and atmospheric forcing. Correlation coef­

ficients between wind and mixed layer depths in the Amazon

region were similar between the tidally forced and non-tidal

simulations, but with greater differences near the coast where

currents and tidal variability were strongest.

Sound Speed and Grid Spacing

Like IGWs, sound speed is also affected by simulation grid spac­

ing. A finer grid may resolve more processes and have differ­

ent temperature and salinity gradients. As an example, we com­

pared two tidally forced simulations with different model setups

to see how model grid-spacing and boundary conditions may

affect sound speed structure: the hydrostatic tidally forced

global HYCOM simulation (Experiment [Exp.] 19.0; 1/25° res­

olution; Figure 5d) and a two-dimensional nonhydrostatic sim­

ulation of the MITgcm (Figure 5e), with a horizontal grid spac­

ing of 100 m. The Mascarene Ridge, where the simulations are

compared, is known for nonlinear wave interactions; solitons are

generated and propagate away from the ridge (Figure 3b,d,f).

Because the simulations were initialized with an offset in tem­

perature, they couldn’t be compared directly; however, a rela­

tive comparison of SLD and BLG was insightful. The HYCOM

simulation had organized semidiurnal fluctuations of the SLD

and BLG, each oscillating twice a day (Figure 5d). In contrast,

the MITgcm simulation had a periodic signal, but it appeared

disorganized, with a more variable SLD and BLG (Figure 5e).

The finer grid spacing of the MITgcm simulation likely allowed

for nonlinear interactions to occur, which in turn impacted

the sound speed structure. This structure is likely closer to real

ocean variability, showing the difficulties of predicting sound

speed using coarser-resolution ocean models.

To address the confounding challenges of the divergent meso­

scale eddy fields and initialization states, we turned to the ide­

alized model (section on Vertical Grid Spacing in Idealized

Models) to isolate the impact of vertical grid spacing on sound

speed. Hourly output from each of the idealized simulations

with 8, 16, 32, 48, and 96 isopycnal layers was interpolated to

a uniform depth coordinate for a 72-hour period. From this

we calculated the sound speed means and standard deviations

(Figure 4c,d). The mean sound speeds were greater in simu­

lations with 32 or fewer layers (Figure 4c) and did not resolve

Oceanography | Vol. 38, No. 2

32

the depth of greatest sound speed variability (Figure 4d). As the

number of layers increased, the mean and standard deviation of

the sound-speed profiles converged, with very little difference

between the 48- and 96-layer simulations. These results parallel

the findings that, for a 1 km horizontal grid spacing, a minimum

of 48 isopycnal layers is necessary to resolve displacement of iso­

pycnals by internal tides.

A DEEP LEARNING APPROACH TO INCLUDING

IGW IN OCEAN MODELS

The finer grid spacing and the inclusion of tidal forcing in ocean

simulations improves the realism of the ocean state. However,

these improvements in a global ocean model are computationally

expensive. To reduce computational cost, we investigated using a

generative adversarial network (GAN; Goodfellow et al., 2014) to

generate a tidally forced ocean state without solving the physical

forcing equations. GANs are a deep learning technique that learn

a transformation from one statistical distribution to another

instead of learning an exact distribution. In a GAN, a “generator,”

which generates new data, is trained alongside a “discriminator,”

which is a classifier that differentiates between actual data and

generated data. The GAN works through iteration, with the gen­

erator learning a distribution transformation and the discrimina­

tor learning to distinguish between real data and generated data.

We trained two pairs of generators and discriminators using

Global HYCOM (1/25°) with (Exp. 19.0) and without (Exp. 19.2)

FIGURE 6. Comparison of acoustic propagation and properties between HYCOM simulations with and without tidal forcing at the Amazon Shelf, starting

at 4.1°N, 44.8°W and extending 30° (clockwise from north) as indicated in Figure 3a. (a) A snapshot from May 20, 2019, 18:00:00 of sound speed (m s–1),

vertical gradient of sound speed (s–1), and transmission loss (TL; dB) for each simulation. (b) A single sound speed profile at 100 km distance along the

radial for the tidal (red) and non-tidal simulation. (c) TL at 20 m depth, sonic layer depth (SLD) and below-layer gradient (BLG). TL is calculated from a

1,500 Hz source at 4.1°N and 44.8°W at 20 m depth.

June 2025 | Oceanography

33

tidal forcing as the initialization states. One generator, GNT→T(·),

translated from the non-tidal to the tidal domain, and the other

generator, GT→NT(·), translated from the tidal to non-tidal

domain. To address the issue of the chaotic, turbulent nature of

the ocean, we considered the simulations to be unpaired (i.e., not

a direct translation between one state and the other). Instead,

the GAN used “cycle-consistency loss,” the mean-squared differ­

ence between the original data sample and the doubly translated

data (Zhu et al., 2017). The cycle-consistency loss was combined

with the traditional GAN losses (i.e., the difference between the

generator and the discriminator output) to train the networks.

The Atlantic Ocean was used as a test-case region; one week of

hourly HYCOM data was split into 90% training data and 10%

validation data.

The GAN results retained the general structure of the tem­

perature and salinity profiles from HYCOM while adding or

removing a semidiurnal tide (Figure 7). The GAN performed

well in the relatively quiescent region of the tropical mid-​

Atlantic (Figure 7b). There, periodic signatures in HYCOM with

tides matched the periodicity of the outputs of GNT→T(·). The

semidiurnal signature was also removed in GT→NT(·) to match

the non-tidally forced HYCOM. It was more difficult to separate

the tidal structure from mesoscale variability in more energetic

regions, such as near the Gulf Stream (Figure 7c,d). For example,

just north of the Gulf Stream (Figure 7c), the GNT→T(·) repro­

duced semidiurnal periodicity of the tidally forced HYCOM,

but there was also periodicity in the nontidal fields. In the Gulf

Stream extension (Figure 7d), the GAN imposed a periodicity to

make the sample like other tidally forced results, but this was a

region dominated by mesoscale variability.

Because the HYCOM output used to train the GAN was sam­

pled from the same region of the globe during the same time of

year, no two samples were completely independent. This intro­

duces the risk of overfitting. Using unpaired data made the

model more robust to overfitting but did not remove the risk

entirely. Additionally, the sound speed structure had a persistent

offset of about 5 m s–1 greater in the GAN-generated results than

the original HYCOM simulations (not shown). Thus, although

this work provides a good starting point, further work will help

revise this approach.

FIGURE 7. Temporal out­

puts of the deep learn­

ing GAN model at the

locations mapped in (a).

For each panel, the first

column shows the non-

tidal (NT) HYCOM results

(Exp 19.2); the second

column shows the NT

results translated into

the tidal domain using

the GAN model; the

third column shows the

tidal (T) HYCOM results

(Exp 19.0); and the fourth

column shows the T

results translated into

the NT domain using a

GAN model. From top

to bottom, rows in (b–d)

show water tempera­

ture, salinity, eastward

velocity, and northward

velocity, respectively.

Oceanography | Vol. 38, No. 2

34

SUMMARY AND CONCLUSIONS

The TFO-HYCOM project was a cross-disciplinary investigation

into the modeling of internal tides and high-frequency IGWS

that explored their sensitivity to grid spacing, energy transfer,

and dissipation; the impacts of tidal forcing in ocean simulations

on sound speed structure and acoustic propagation; and the

ability to use DL techniques to replicate tidally forced structure.

The inclusion of tidal forcing in global ocean models improved

the representation of the ocean state and had a direct impact on

sound speed at horizontal scales from kilometers to hundreds of

kilometers and timescales on the order of a few to several hours.

HYCOM simulations run with tides had greater sound-speed

variance that was more consistent with observations. These

impacts were sensitive to vertical and horizontal discretization,

as were the ability of the simulations to resolve IGW interactions

and energy transfer. Further investigations into the impacts of

internal wave modeling choices on acoustic propagation could

also be made by expanding acoustic frequency ranges, looking at

acoustic arrival times, or comparing model results with observa­

tional studies. As running models at high resolution is compu­

tationally expensive, machine learning techniques may facilitate

predictions of IGW impacts on ocean state in the future.

We have focused on the impacts of IGWs on sound; how­

ever, global ocean models are further used by stakeholders with

diverse interests, such as the dispersal of biogeochemical tracers

and biological productivity. As global operational models begin

to include tidal forcing and incorporate finer grid spacing, it is

important to understand how they represent physical processes

and how energy cascades through the internal wave spectrum.

The ability to resolve IGWs in global ocean models has filter-​

down effects to several other fields such as ocean biological-​

physical interactions and ecosystem modeling. At shallow coastal

locations, where biological productivity and fresh­water input are

large, the ability to resolve these IGW processes is important to

understanding ecosystem dynamics. Among the range of their

impacts, IGWs can alter distributions of organisms such as phy­

toplankton and chlorophyll, increase or decrease biological pro­

ductivity, and alter predator-prey relationships (e.g., Evans et al.,

2008; Lucas et al., 2011; Greer et al, 2014; Garwood et al., 2020).

Having criteria for how IGWs can be resolved in a global model

with a certain discretization will help interpret how well a model

captures IGW energy transfer and the possible effects this may

have on sound speed variability and ecosystem dynamics.

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ACKNOWLEDGMENTS

This TFO-HYCOM project was funded by related Office of Naval Research (ONR)

grants to the different institutions involved: N00014-19-1-2712 to University of

Michigan, N00014-19-1-2717 to Florida State University, N00014-19-1-2704 to

University of Southern Mississippi, N00014-20-C-2018 to ARiA and Applied Ocean

Sciences LLC, and contract number N00014-22WX00941 to the Naval Research

Laboratory. We gratefully acknowledge ONR for support of our research and thank

the reviewers of this article for their helpful suggestions and insights.

AUTHOR CONTRIBUTIONS

This manuscript highlights the research efforts by postdocs and early career

researchers on the TFO-HYCOM project. The team was guided by senior scien­

tist co-PIs at each institution. J. Summers served as lead principal investigator.

B. Arbic conceived the idea of a project and organized regular group meetings.

The team that focused on improving IGW modeling was composed of research­

ers from the Naval Research Laboratory (NRL), Florida State University (FSU),

University of Southern Mississippi (USM), and University of Michigan (U-M). The

NRL team provided 1/25º global HYCOM simulations. FSU researchers performed

1/50º North Atlantic basin simulations and idealized simulations. USM research­

ers examined IGW modes and KE transfer and provided MITgcm simulations along

the Mascarene Ridge, while U-M researchers examined the theory of IGW non­

linear energy transfer and dissipation in high-resolution regional MITgcm simula­

tions. Researchers from NRL and Applied Ocean Sciences assessed acoustics,

and researchers from Applied Research in Acoustics LLC applied deep learning

algorithms. Figures were contributed as follows: 3g–h, 5d–e, 6, and 7a (Schönau);

4 (Hiron); 7b–d (Ragland and Peria); 2a–b and 3a–f (Solano); 1 (Xu); 5a–c (Shriver

and Helber); 2c (Buijsman).

AUTHORS

Martha C. Schönau (mschonau@ucsd.edu), formerly at Applied Ocean Sciences

(AOS), now at Scripps Institution of Oceanography, University of California

San Diego, La Jolla, CA, USA. Luna Hiron, Center for Ocean-Atmospheric

Prediction Studies, Florida State University, Tallahassee, FL, USA. John Ragland,

Applied Research in Acoustics LLC (ARiA) and Department of Electrical

and Computer Engineering, University of Washington, Seattle, WA, USA.

Keshav J. Raja, Center for Ocean-Atmospheric Prediction Studies, Florida State

University, Tallahassee, FL, USA. Joseph Skitka, formerly in the Department of

Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA,

now in the Department of Physical Oceanography, Woods Hole Oceanographic

Institution, Woods Hole, MA, USA. Miguel S. Solano, formerly in the School

of Ocean Science and Engineering, The University of Southern Mississippi,

Hattiesburg, MS, USA, now at Sofar Ocean Technologies, San Francisco, CA,

USA. Xiaobiao Xu, Center for Ocean-Atmospheric Prediction Studies, Florida

State University, Tallahassee, FL, USA. Brian K. Arbic, Department of Earth

and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA.

Maarten C. Buijsman, School of Ocean Science and Engineering, The University

of Southern Mississippi, Hattiesburg, MS, USA. Eric P. Chassignet, Center for

Ocean-Atmospheric Prediction Studies, Florida State University, Tallahassee,

FL, USA. Emanuel Coelho, AOS, Arlington, VA, USA. Robert W. Helber, Naval

Research Laboratory, Ocean Dynamics and Prediction, Stennis Space Center,

MS, USA. William Peria, ARiA, Seattle, WA, USA. Jay F. Shriver, Naval Research

Laboratory, Ocean Dynamics and Prediction, Stennis Space Center, MS, USA.

Jason E. Summers, ARiA, Seattle, WA, USA. Kathryn L. Verlinden, AOS, Portland,

OR, USA. Alan J. Wallcraft, Center for Ocean-Atmospheric Prediction Studies,

Florida State University, Tallahassee, FL, USA.

ARTICLE CITATION

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B.K. Arbic, M.C. Buijsman, E.P. Chassignet, E. Coelho, R.W. Helber, W. Peria,

J.F. Shriver, J.E. Summers, K.L. Verlinden, and A.J. Wallcraft. 2025. How do tides

affect underwater acoustic propagation? A collaborative approach to improve

internal wave modeling at basin to global scales. Oceanography 38(2):24–35,

https://doi.org/10.5670/oceanog.2025.308.

COPYRIGHT & USAGE

This is an open access article made available under the terms of the Creative

Commons Attribution 4.0 International License (https://creativecommons.org/

licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and repro­

duction in any medium or format as long as users cite the materials appropriately,

provide a link to the Creative Commons license, and indicate the changes that

were made to the original content.

Oceanography | Vol. 38, No. 2

36

FEATURE ARTICLE

FROM WIND TO WHALES

POTENTIAL HYDRODYNAMIC IMPACTS OF OFFSHORE WIND

ENERGY ON NANTUCKET SHOALS REGIONAL ECOLOGY

By Eileen E. Hofmann, Jeffrey R. Carpenter, Qin J. Chen, Josh T. Kohut, Richard L. Merrick, Erin L. Meyer-Gutbrod,

Douglas P. Nowacek, Kaustubha Raghukumar, Nicholas R. Record, and Kelly Oskvig

WIND TO WHALES:

CONSENSUS STUDY SUMMARY

Large-scale offshore wind farm development is planned and par­

tially underway for US continental shelf waters. The potential

oceanographic impacts from this development remain as open

questions. The Nantucket Shoals region on the US continental

shelf off the coast of Massachusetts is one area designated for

wind farm development (Figure 1a,b). The oceanography of this

region is complex (Figure 1c), and warming water temperatures

in the North Atlantic, marine heatwaves, and Gulf Stream vari­

ability are enhancing and changing the natural oceanographic

variability of this region, as summarized in the accompanying

Perspective (Gawarkiewicz, 2025, in this issue). The addition

of extensive wind farms composed of many individual turbines

is anticipated to impose additional oceanographic variability

that may change the hydrodynamic environment through flow

past turbine structures and removal of wind energy (Figure 1d).

This additional variability potentially affects hydrodynamic pro­

cesses at scales ranging from individual turbines to wind farms to

regional (Figure 1; Gawarkiewicz, 2025, in this issue). Separating

the effects of wind energy installations from natural hydro­

dynamic variability presents new challenges for the oceano­

graphic observing and modeling communities.

Changes in hydrodynamic processes can also affect phyto­

plankton and zooplankton production, distribution, and avail­

ability, with consequences for higher trophic level organisms

(Figure 1d). Of particular concern for the Nantucket Shoals

region are hydrodynamic changes that may affect the distribu­

tion and availability of zooplankton species, especially the cope­

pods (e.g.,  Calanus finmarchicus, Centropages spp., Oithonia

similis), that are primary prey for the critically endangered

North Atlantic right whale (Eubalaena glacialis) that forages in

the region (Sorochan et al., 2021). As noted in the accompany­

ing Perspective by Saba (2025, in this issue), copepod species are

transported from upstream sources by coastal currents into the

Nantucket Shoals region where they form dense aggregations that

are targeted by right whales. The concern is that hydrodynamic

variability resulting from turbines and wind farms may modify

these processes, causing disruptions in prey availability for right

whales (Saba, 2025, in this issue). However, the advective sup­

ply and physical-biological processes that allow dense copepod

aggregations to form are not well understood (Saba, 2025, in

this issue). The different scenarios presented by Saba (2025, in

this issue) suggest that assessing offshore wind energy develop­

ment effects on Nantucket Shoals ecosystem production will first

require identification and quantification of the relevant processes.

Given the concern about potential offshore wind farm effects

on hydrodynamics at local to regional ecosystem scales, the

Bureau of Ocean Energy Management (BOEM) requested that

the National Academies of Science, Engineering, and Medicine

evaluate the potential for offshore wind farms in the Nantucket

Shoals region to modify area hydrodynamics with impacts on

ABSTRACT. The National Academy of Sciences, Engineering, and Medicine convened a committee in June 2023 to assess the

potential hydrodynamic and ecological impacts from offshore wind energy development in the Nantucket Shoals region, with par­

ticular attention to impacts on the critically endangered North Atlantic right whale (Eubalaena glacialis) that forages on zooplankton

aggregations in the region. The assessment suggested that the effects of offshore wind energy development will be difficult to distin­

guish from the effects of natural variability and climate change in this region. The Consensus Study Report recommendations high­

light observational and modeling studies that will advance understanding of potential hydrodynamic effects and impacts on the ecol­

ogy of the region. A subsequent workshop provided guidance on observational needs and approaches for a field monitoring program

to advance model capability to simulate effects of offshore wind energy development on Nantucket Shoals hydrodynamics and ecol­

ogy. Observational and modeling programs implemented for the Nantucket Shoals region will inform other regions of the US East

Coast continental shelf that have been designated for offshore wind energy development.

June 2025 | Oceanography

37

FIGURE 1. (a) Nantucket Shoals region with proposed wind lease areas indicated (gray shading). (b) Offshore wind farm showing poten­

tial wind reduction and ocean turbulence effects (swirls) from wind turbine structures. (c) Schematic of oceanographic processes that

influence the hydrodynamics of the Nantucket Shoals region (adapted from Gawarkiewicz and Plueddemann, 2020). (d) Schematic

of potential wind turbine effects. The wind, blowing from left to right, decreases in energy as it passes the turbine. Ocean circulation,

flowing from left to right, becomes more turbulent downstream of the turbine (indicated by swirls) with potential effects on water col­

umn stratification (gradient shading with red to blue indicating transition from low-density surface water to more dense water at depth).

Ecological effects of a turbine extend from phytoplankton to whales. The turbine, phytoplankton, zooplankton, and higher trophic level

organisms are not shown to scale.

Oceanography | Vol. 38, No. 2

38

the ecology of the region. The Committee on Evaluation of

Hydrodynamic Modeling and Implications for Offshore Wind

Development: Nantucket Shoals was convened in June 2023.

This summary provides the findings and recommendations from

the resulting Consensus Study Report (NASEM, 2024a) as well

as from a subsequent BOEM-sponsored workshop (NASEM,

2024b). The accompanying Perspectives by Gawarkiewicz

(2025) and Saba (2025) provide additional insights about off­

shore wind energy development in the Nantucket Shoals region.

Evaluation of the understanding of potential hydrodynamic

effects of offshore wind farms, based on observations and model­

ing studies for wind installations in European waters, shows that

offshore wind turbines can alter local hydrodynamics by inter­

rupting circulation processes through a wake effect and induce

turbulence in the water column surrounding and downstream

of the turbine (Figure 1d; e.g., Schultze et al., 2020). Wind speed

reduction occurs downstream of the turbines, but its effects on

the sea surface are poorly understood (Golbazi et  al., 2022).

These effects become more complex when extended to arrays

of turbines in an offshore wind farm or multiple adjacent wind

farms with implications for both local and regional circulation.

Evaluation of these complex interactions with hydrodynamic

models requires that key processes be included at appropri­

ate spatial and temporal scales. The limited studies to date sug­

gest that the hydrodynamic effects of turbines will be difficult

to isolate from the much larger variability introduced by natu­

ral and other anthropogenic sources (including climate change;

Schultze et al., 2020; Floeter et al., 2017, 2022). These findings

support two recommendations for observations and modeling

studies for assessing the hydrodynamic impacts of offshore wind

energy installations in US continental shelf waters:

• RECOMMENDATION. The Bureau of Ocean Energy Manage­

ment, the National Oceanic Atmospheric Administration, and

others should promote, and where possible require, observa­

tional studies during all phases of wind energy development—​

surveying, construction, operation, and decommission­

ing—​that target processes at the relevant turbine-​to-​wind

farm scales to isolate, quantify, and characterize their hydro­

dynamic effects. Studies at Block Island, Dominion, Vineyard

Wind I, and South Fork Wind should be considered as case

study sites given their varying numbers of turbines, types of

foundations, and sizes and spacing of turbines.

• RECOMMENDATION. The Bureau of Ocean Energy Manage­

ment, the National Oceanic Atmospheric Administration,

and others should require model validation studies to deter­

mine the capability and appropriateness of a particular model

to simulate key baseline hydrodynamic processes relevant at

turbine, wind farm, and/or regional scales.

The ecological impacts of offshore wind structures can poten­

tially affect all trophic levels (Figure 1d), and changes in zoo­

plankton production, supply, and aggregation may affect right

whales that have been frequently observed feeding in the

Nantucket Shoals region and other areas of high productivity in

Southern New England waters.

Evaluation of the potential impacts on right whale prey show

that the paucity of observations and the uncertainty of mod­

eled hydrodynamic effects make it difficult to assess the eco­

logical impacts of offshore wind farms, particularly considering

the scale of both natural and human-caused variability in the

Nantucket Shoals region. Studies to date do not have the spatial

and temporal coverage at the proposed wind energy lease sites to

adequately capture broad-scale right whale use of this region and

potential impacts from offshore wind farms. Additionally, forag­

ing by right whales in the region is not fully understood, includ­

ing the basic question of which zooplankton taxa right whales

are feeding on and how this prey changes seasonally. Models are

needed that can effectively incorporate the supply and behavior

of zooplankton as well as the physical oceanographic processes

that aggregate zooplankton in the Nantucket Shoals region.

The impacts of offshore wind projects on the right whale and

the availability of its prey in the Nantucket Shoals region will

likely be difficult to distinguish from the significant impacts of

climate change and other influences on the ecosystem. As plan­

ning and construction of wind farms in the Nantucket Shoals

region continue, further study and monitoring of the oceanog­

raphy and ecology of the area are needed to fully understand

the impact of future wind farms. Advancing understanding of

potential impacts is especially important as right whale use of

the region continues to evolve (e.g., O’Brien et al., 2022).

These findings support two recommendations for observa­

tions and modeling studies for assessing the ecological impacts

of offshore wind energy installations:

• RECOMMENDATION. The Bureau of Ocean Energy Manage­

ment, the National Oceanic Atmospheric Administration, and

others should support, and where possible require, the collec­

tion of oceanographic and ecological observations through

robust integrated monitoring programs within the Nantucket

Shoals region and in the region surrounding wind energy

areas before and during all phases of wind energy develop­

ment: surveying, construction, operation, and decommis­

sioning. This is especially important as right whale use of the

Nantucket Shoals region continues to evolve due to oceano­

graphic changes and/or the activities and conditions relevant

to offshore wind farms.

• RECOMMENDATION. The Bureau of Ocean Energy Manage­

ment, the National Oceanic Atmospheric Administration, and

others should support, and where possible require, ocean­

ographic and ecological modeling of the Nantucket Shoals

region before and during all phases of wind energy develop­

ment: surveying, construction, operation, and decommission­

ing. This critical information will help guide regional policies

that protect right whales and improve predictions of ecologi­

cal impacts from wind development at other lease sites.

June 2025 | Oceanography

39

Subsequent to the Consensus Study Report, a workshop was

convened in July 2024 to design a field monitoring program

that would respond to the Consensus Study Report recom­

mendations. The diverse expertise of the workshop participants

facilitated discussions of observational needs and approaches

for a field monitoring program to advance models developed

to assess potential effects of offshore wind energy development

on Nantucket Shoals hydrodynamics and ecology (NASEM,

2024b). The workshop proceedings identified for the turbine

and wind farm scales (1) parameters that should be measured

with a focus on the oceanographic and atmospheric parame­

ters necessary to drive models, and (2) specific components for

implementing a field monitoring program to resolve key phys­

ical and ecological features and processes to improve under­

standing of potential effects of offshore wind energy develop­

ment on Nantucket Shoals ecology, including the right whale.

There was agreement that existing monitoring programs pro­

vide important information but that coordination within and

across these efforts is needed and that models and syntheses

of existing data should be used to guide the design of obser­

vations and field programs. The workshop discussions pointed

to a set of science priorities that respond to the recommenda­

tions from the Consensus Study, such as monitoring designed

to isolate wind farm impacts from natural and anthropo­

genic variability and studies to advance understanding of prey

aggregation processes. The convening of the workshop was an

important step toward identifying resources and a timeline for

implementing field and modeling studies that address concerns

about the effects of offshore wind energy development in the

Nantucket Shoals region.

Although the hydrodynamic effects of offshore wind devel­

opment on the Nantucket Shoals region ecology are not yet well

understood, the current state of knowledge and key directions

for advancing this understanding are reflected in the Consensus

Study Report (NASEM, 2024a). The Workshop Proceedings

(NASEM, 2024b) points to specific observational and model­

ing activities that could be implemented to begin to address

the Consensus Study recommendations. The Perspectives pro­

vided by Gawarkiewicz (2025) and Saba (2025) in this issue

reinforce the need to advance understanding of the hydro­

dynamics and ecology of the important Nantucket Shoals

region. Observational and modeling approaches developed for

Nantucket Shoals will provide a framework for areas along the

US East Coast continental shelf that are slated for offshore wind

energy development over the next decade. It remains for the

oceanographic community to undertake the observational and

modeling programs necessary to assess the effects of offshore

wind energy development on hydrodynamics and the corre­

sponding impact on ecosystems, and for government agencies

and the wind energy industry to provide resources for imple­

mentation of these programs.

REFERENCES

Floeter, J., J.E.E. van Beusekom, D. Auch, U. Callies, J. Carpenter, T. Dudeck,

S. Eberle, A. Eckhardt, D. Gloe, K. Hänselmann, and others. 2017. Pelagic effects

of offshore wind farm foundations in the stratified North Sea. Progress in

Oceanography 156:154–173, https://doi.org/10.1016/j.pocean.2017.07.003.

Floeter, J., T. Pohlmann, A. Harmer, and C. Möllmann. 2022. Chasing the offshore

wind farm wind-wake-induced upwelling/downwelling dipole. Frontiers in Marine

Science 9:884943, https://doi.org/10.3389/fmars.2022.884943.

Gawarkiewicz, G., and A.J. Plueddemann. 2020. Scientific rationale and concep­

tual design of a process-oriented shelf break observatory: The OOI Pioneer

Array. Journal of Operational Oceanography 13(1):19–36, https://doi.org/10.1080/​

1755876X.​2019.1679609.

Gawarkiewicz, G. 2025. Setting a course for research on offshore wind develop­

ment impacts near Nantucket Shoals. Oceanography 38(2):5–6, https://doi.org/​

10.5670/oceanog.2025.303.

Golbazi, M., C.L. Archer, and S. Alessandrini. 2022. Surface impacts of large off­

shore wind farms. Environmental Research Letters 17:064021, https://doi.org/​

10.1088/1748-9326/ac6e49.

NASEM (National Academies of Science, Engineering, and Medicine). 2024a.

Potential Hydrodynamic Impacts of Offshore Wind Development on Nantucket

Region Ecology: An Evaluation from Wind to Whales. The National Academies

Press, Washington, DC, 120 pp., https://doi.org/10.17226/27154.

NASEM. 2024b. Nantucket Shoals Wind Farm Field Monitoring Program:

Proceedings of a Workshop. The National Academies Press, Washington, DC,

64 pp., https://doi.org/10.17226/28021.

O’Brien, O., D.E. Pendleton, L.C. Ganley, K.R. McKenna, R.D. Kenney, E. Quintana-

Rizzo, C. A. Mayo, S.D. Kraus, and J.V. Redfern. 2022. Repatriation of a histor­

ical North Atlantic right whale habitat during an era of rapid climate change.

Scientific Reports 12(1):12407, https://doi.org/10.1038/s41598-022-16200-8.

Saba, G.K. 2025. Zooplankton and offshore wind: Drifters in a sea of uncertainty.

Oceanography 38(2):7–9, https://doi.org/10.5670/oceanog.2025.302.

Schultze, L.K.P., L.M. Merckelbach, J. Horstmann, S. Raasch, and J.R. Carpenter.

2020. Increased mixing and turbulence in the wake of offshore wind farm foun­

dations. Journal of Geophysical Research: Oceans 125(8):e2019JC015858,

https://doi.org/10.1029/2019JC015858.

Sorochan, K.A., S. Plourde, M.F. Baumgartner, and C.L. Johnson. 2021. Availability,

supply, and aggregation of prey (Calanus spp.) in foraging areas of the

North Atlantic right whale (Eubalaena glacialis). ICES Journal of Marine

Science 78(10):3498–3520, https://doi.org/10.1093/icesjms/fsab200.

ACKNOWLEDGMENTS

The committee thanks the study sponsor, the Bureau of Ocean Energy Manage­

ment (BOEM), and BOEM staff who helped with the study, especially Mary

Boatman, Desray Reeb, and Thomas J. Kilpatrick. Thanks also go to the speakers

who joined the committee meetings and information gathering workshop to inform

and enrich discussions that led to the Consensus Study Report. The efforts of the

individuals who provided their diverse perspectives and technical expertise to the

review of the Consensus Study Report are gratefully acknowledged. Lastly, thanks

are extended those who participated in the follow-on workshop (July 9–10, 2024)

and generously provided their ideas for observations and field monitoring studies

that support the recommendations from the Consensus Study Report.

AUTHORS

Eileen E. Hofmann (hofmann@ccpo.odu.edu), Old Dominion University, Norfolk,

VA, USA. Jeffrey R. Carpenter, Institute for Coastal Ocean Dynamics, Helmholtz-

Zentrum Hereon, Geesthacht, Germany. Qin J. Chen, Northeastern University,

Boston, MA, USA. Josh T. Kohut, Rutgers University, New Brunswick, NJ, USA.

Richard L. Merrick, retired, National Oceanic and Atmospheric Administration,

Silver Spring, MD, USA. Erin L. Meyer-Gutbrod, University of South Carolina,

Columbia, SC, USA. Douglas P. Nowacek, Duke University, Durham, NC,

USA. Kaustubha Raghukumar, Integral Consulting Inc., Santa Cruz, CA, USA.

Nicholas R. Record, Bigelow Laboratory for Ocean Sciences, East Boothbay, ME,

USA. Kelly Oskvig, National Academies of Sciences, Engineering, and Medicine,

Washington, DC, USA.

ARTICLE CITATION

Hofmann, E.E., J.R. Carpenter, Q.J. Chen, J.T. Kohut, R.L. Merrick, E.L. Meyer-

Gutbrod, D.P. Nowacek, K. Raghukumar, N.R. Record, and K. Oskvig. 2025. From

wind to whales: Potential hydrodynamic impacts of offshore wind energy on

Nantucket Shoals regional ecology. Oceanography 38(2):36–39, https://doi.org/​

10.5670/​oceanog.2025.304.

COPYRIGHT & USAGE

This is an open access article made available under the terms of the Creative

Commons Attribution 4.0 International License (https://creativecommons.org/

licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and repro­

duction in any medium or format as long as users cite the materials appropriately,

provide a link to the Creative Commons license, and indicate the changes that

were made to the original content.

Oceanography | Vol. 38, No. 2

40

Oceanography

40

FEATURE ARTICLE

OVERVIEW OF THE

ATLANTIC DEEPWATER ECOSYSTEM

OBSERVATORY NETWORK

By Jennifer L. Miksis-Olds, Michael A. Ainslie,

Hannah B. Blair, Thomas Butkiewicz, Elliott L. Hazen,

Kevin D. Heaney, Anthony P. Lyons, Bruce S. Martin,

and Joseph D. Warren

Deployment of an ADEON Autonomous

Long-Term Observation lander off

R/V Endeavor. Photo Credit: Jennifer

Miksis-Olds, University of New Hampshire

Oceanography | Vol. 38, No. 2

40

June 2025 | Oceanography

41

INTRODUCTION

Events such as fish stock collapse, coastal flooding during severe

storms, and major oil and other toxic spills, along with the

need for the conservation of protected and endangered species

including many marine mammals, are making ocean users and

the broader public increasingly aware of the need for responsible

marine stewardship. Interest in responsible planning and man­

agement of ocean resources has sparked international research

programs that are measuring baseline conditions that can be

used to assess current effects and future variations, trends, and

impacts. Through the National Oceanographic Partnership

Program (NOPP), the Bureau of Ocean Energy Management

(BOEM), Office of Naval Research (ONR), and National

Oceanic and Atmospheric Administration (NOAA) contracted

a team led by the University of New Hampshire to develop and

deploy the Atlantic Deepwater Ecosystem Observatory Network

(ADEON), whose objective was to improve the understand­

ing of marine soundscapes and their relation to the ecosystem

of the US Atlantic deep waters. Marine ecosystem monitoring

supports the mandates of multiple federal agencies that seek to

understand and mitigate human impacts on the offshore envi­

ronment. Long-term observations of living marine resources

and marine sound inform compliance with the US Endangered

Species Act, the Marine Mammal Protection Act, and the

Sustainable Fisheries Act, while physicochemical measurements

of water and air quality help inform agency compliance with the

Clean Water and Clean Air Acts.

Although there has been extensive hydrographic research

along the South Atlantic OCS (e.g., Lee et al., 1991; Atkinson

et al., 1983; Lee and Atkinson, 1983), knowledge of the ocean

soundscape and its relationship to regional OCS dynamics is rel­

atively unexplored. Ocean sound is now an accepted Essential

Ocean Variable in the Global Ocean Observing System (Tyack

et al., 2023) due to its wide utility as an indicator of physical and

biological ocean processes. Sound travels efficiently underwater,

making it the dominant modality that marine life and humans

alike use to sense and respond to the changing environment;

information provided by underwater acoustic methodologies

has become critical to applications spanning national secu­

rity, adaptive management of marine resources, monitoring of

climate change, tsunami warning, and search and rescue (Howe

et al., 2019). Thus, understanding the unique and complex rela­

tionship between ocean sound and the environment at regional

scales is vital to assessing any projected impact of immediate or

forecasted change related to climate or human use.

A full contextual description of the relationship between

marine organisms and their environments, including acous­

tics, is lacking (Hawkins and Popper, 2017). The effects of expo­

sure of marine organisms to intense sounds is becoming bet­

ter understood; however, the long-term cumulative effects from

noise-generating sources, including seismic surveys, offshore

wind energy, military and shipping vessels, and recreational

boating, is not well understood. Hence, there is a critical need

to work toward comprehensive knowledge of the interactions

between marine life and the ocean soundscape, defined as the

auditory scene in a region resulting from biologic (marine life),

geologic (non-biological natural sound such as wind, precipi­

tation, and ice), and anthropogenic (human activity) contribu­

tions to the soundscape, characterized by the ambient sound

in terms of its spatial, temporal, and frequency attributes, and

the types of sound sources (ISO 18405, 2017). ADEON was

designed to synoptically record ocean sound and ecosystem

indicators of biomass, conductivity, temperature, and dissolved

oxygen (CT-DO). Measurements from stationary, mobile, and

space-based platforms (Figure 1a) were combined to provide

context for understanding and modeling how environmental

variability manifests in the regional soundscape.

ADEON was structured into four major technical

phases: (1) Network Design, Equipment Procurement, and

Deployment; (2) Data Acquisition and Network Maintenance;

(3) Data Processing, and (4) Data Integration and Visualization.

During the proposal development stage, the ADEON team

recognized a lack of community-wide standardization for

ocean soundscape data and data products. Thus, standardiza­

tion was an overarching effort elevated above the four techni­

cal phases that generated products for soundscape terminol­

ogy, data acquisition, processing, and reporting. In fulfillment

of the NOPP requirement to make all data and products pub­

licly available, all raw data are publicly available through the

NOAA National Centers for Environmental Information

ABSTRACT. The Atlantic Deepwater Ecosystem Observatory Network (ADEON) along the US Mid- and South Atlantic Outer

Continental Shelf (OCS) collected multiple years of measurements that describe the ecology and soundscape of the OCS. Ocean pro­

cesses, marine life dynamics, and human use of the ocean are each three dimensional and time dependent, and occur at many spatial

and temporal scales. Because no single measurement system (in situ or remote) is sufficient for describing dynamic ocean variables,

the approach taken by ADEON was to integrate ocean measurements and models. Acoustic information was combined with contex­

tual data from space-based remote sensing, hydrographic sensors, and mobile platforms in order to fully comprehend how human,

biologic, and natural abiotic components create the OCS soundscape and influence its ecosystem dynamics. Standardized methodol­

ogies were developed for comparing soundscapes across regions and for generating predictive models of the soundscape and overall

ecology of the OCS at 200–900 m water depths. These data provide a baseline for pattern and trend analyses of ambient sound and

the ecosystem components of the OCS soundscapes. They contribute to understanding of regional processes over multi-year time­

scales and support ecosystem-based management of marine resources in an acoustically under-sampled ocean region.

Oceanography | Vol. 38, No. 2

42

(https://www.ncei.noaa.gov/products/passive-acoustic-data),

and all processed data products are accessible through the

ADEON Data Portal (https://adeon.unh.edu/data_portal).

SIGNIFICANT CONTRIBUTIONS

The overarching goal of ADEON was to establish an integrated,

deep-water acoustical observing system for the US Mid- and

South Atlantic OCS that generated year-round measurements of

the natural and human factors driving the regional ecology and

soundscape over several years and that are transferable to other

locations. To meet this goal, the program generated new tech­

nology, infrastructure, measurement, and analysis approaches

that have since been applied to other regions. The ADEON effort

went beyond data collection and analyses related to monitor­

ing ecosystem components to perform basic science and pub­

licly disseminate the data to support future research. Science

and innovation accomplishments of ADEON include (1) devel­

opment and implementation of standardized acoustic metrics

and practices across ADEON components that are serving as

a model for national and international soundscape programs,

(2) development of an Autonomous Long-Term Observation

(ALTO) lander that simultaneously records acoustic (passive

and active) and oceanographic information, (3) identification

of the horizontal range of extrapolation for acoustic backscat­

ter point samples recorded at each lander location for guiding

future monitoring designs (Blair et al., 2021), (4) documenta­

tion of minke whale winter mating grounds in the southern

and offshore waters of the Blake Plateau (Kowarski et al., 2022),

(5) determination of site fidelity of beaked whale species along

the southeastern US OCS (Kowarski et al., 2022), (6) model-data

comparison of combined wind and vessel soundscape model

levels (Heaney et al., 2024), (7) modeling of regional ecology to

predict potential influences of long-term change on marine eco­

systems, and (8) development of web-based tools to access and

visualize multi-dimensional data streams.

The ADEON team established a long-term (three-year)

observing network that provided the first publicly avail­

able, multi-​location (seven sites), wide-band (10–7,000 Hz),

FIGURE 1. (a) Data was collected for the Atlantic Deepwater Ecosystem Observatory Network (ADEON) using fixed and mobile platforms, shipboard

sampling, and satellite remote sensing. (b) Schematic of the Autonomous Long-Term Observatory (ALTO) landers used in ADEON. Hydrophones were

spaced between 0.45 m and 0.68 m. (c) ADEON sites overlayed with bathymetry. Standard landers had a passive acoustic system and oceanographic

sensors. The Standard with the Acoustic Zooplankton Fish Profiler (AZFP, ASL Environmental Sciences, Canada) landers had the addition of an echo

sounder system. (d) ADEON sites ordered from north to south.

June 2025 | Oceanography

43

directional passive acoustic dataset and associated environmen­

tal time series from an acoustically undersampled region of the

United States Exclusive Economic Zone along the southeast­

ern OCS. Data collected are applicable to marine spatial plan­

ning and ecosystem-based management, and they also pro­

vide a mechanistic understanding of cumulative impacts on

marine resources. ADEON acquired measurements and devel­

oped objective metrics that enabled a quantitative assessment

of the Mid- and South Atlantic Ocean region soundscape, with

consideration of ecosystem conditions, as they may be linked

to extant biologic, geophysical-chemical, and/or anthropogenic

processes. Consideration was also given to resolving periodic­

ities in regional processes over long timescales to establish an

acoustic baseline for extracting trends and for comparing to his­

torical oceanographic time series in the region.

ADEON MULTI-PLATFORM APPROACH

The backbone of the measurement program was the ALTO

lander developed by JASCO Applied Sciences specifically for

the ADEON program (Figure 1b). The lander sensors included

a passive, four-channel autonomous acoustic recorder (AMAR),

a four-frequency echo sounder (Acoustic Zooplankton Fish

Profiler – AZFP by ASL Environmental Sciences, Canada), a

VEMCO VR2W fish tag receiver, and a Sea-Bird-37 CT-DO

unit. This combination of technology is transferable and relo­

catable and has been successfully deployed by other projects and

in additional regions since the conclusion of ADEON, including

AEON (Acoustic and Environmental Observation Network in

the NW Atlantic; https://eos.unh.edu/aeon), multiple projects to

monitor the movement of marine mammals around oil and gas

developments off Canada and Australia, and many wind farm

developments in the United States, Scotland, and Australia.

Lander sites were selected by considering ecological rele­

vance, diversity of anthropogenic activities, 200–900 m target

depth range (with three sites less than 400 m deep to accommo­

date the echosounder depth maximum), sufficient along-shelf

and across-shelf comparisons, and locations of other known

observation assets to support the analysis of soundscape por­

tability (Figure 1c,d). Five University-National Oceanographic

Laboratory System (UNOLS) cruises were devoted to servic­

ing lander deployments, turnarounds, and recovery and also

supported vessel-based, biological net tows performed during

fine-scale acoustic surveys (FSASs) of water column backscat­

ter, marine mammal surveys, full water column CTD casts,

and acoustic propagation characterization at each lander loca­

tion. Kowarski et al. (2022) present the details of the deploy­

ment dates, durations, and AMAR lander passive acoustic

array parameters.

The landers were deployed from November/December 2017

to December 2020. The four-channel AMARs sampled approx­

imately 45 minutes of each hour, alternating between a single

channel at 16 kHz sampling rate for 20 minutes, all four channels

at 16 kHz for 20 minutes, and a high frequency 512 kHz sam­

pling rate for a total of five minutes. The echo sounder system

sampling for 10–12 minutes each hour occurred during the por­

tion of the hour when the AMAR was sleeping to eliminate con­

tamination of the passive acoustic recordings. The AZFP emitted

a 750 μs ping every four seconds during the 10–12 minute sam­

pling period. The CT-DO unit sampled every 30 minutes.

To link the long-term measurements to environmental con­

ditions, the network design included remote sensing of oceanic

and atmospheric variables to be used as covariates in the eco­

system and soundscape models. These data included: (1) auto­

mated identification system (AIS) ship tracks, (2) sea sur­

face temperature (a combination of data from the NASA Jet

Propulsion Laboratory [JPL] and Copernicus), (3) chlorophyll a

concentrations obtained from the NASA-NOAA Visible Infrared

Imaging Radiometer Suite (VIIRS) onboard the Suomi National

Polar-orbiting Partnership (SNPP) satellite, (4) net primary pro­

ductivity derived from NASA using the Vertically Generalized

Production Model (VGPM) by Behrenfeld and Falkowski (1997),

(5) mixed layer depth derived from the Hybrid Coordinate

Ocean Model (HYCOM), (6) wind speed and direction from

the Advanced SCATterometer (ASCAT) real aperture sensor

onboard the meteorological operational platforms of the French

Institute for Ocean Science (IFREMER), and (7) upper surface

current speed and direction from the Ocean Surface Current

Analysis Real-time (OSCAR) project at JPL. The final element of

the network design incorporated mobile measurements that pro­

vided a broader context for the long-term measurements. These

consisted of data from the FSASs performed by the lander ser­

vice vessel, a horizontal array of hydrophones towed by a drifting

sailboat, and an autonomous sailboat that measured variability

of the soundscape between lander locations and across the Gulf

Stream—the dominant regional oceanographic feature.

ADEON STANDARDS

The standardization component of ADEON increased the value

of its data by providing products comparable to data from other

national and international acoustic programs. ADEON adopted

the international standard for underwater acoustical terminol­

ogy ISO 18405 Underwater acoustics – Terminology (ISO 18405,

2017; Ainslie et  al., 2021), compatible with the International

System of Units (BIPM 2019) and the International System of

Quantities (ISO 80000-8 Quantities and units – Acoustics). A

dictionary of terms was created to facilitate internal commu­

nication among project team members as well as with exter­

nal stakeholders. The ADEON Project Dictionary: Terminology

Standard (https://doi.org/10.6084/m9.figshare.12436199.v2) was

also used by the Joint Monitoring Programme for Ambient Noise

in the North Sea (JOMOPANS; Robinson and Wang, 2021), the

EU’s SATURN program (Ainslie et al., 2024), and ISO/DIS 7605

Underwater Acoustics—Measurement of Underwater Ambient

Sound

(https://www.iso.org/standard/82844.html).

ADEON

Oceanography | Vol. 38, No. 2

44

terminology was also adopted in recommendations from two

international workshops, one in Dublin in 2016 (Ainslie et al.,

2019) and one in Berlin in 2022 (Martin et  al., 2024), and it

served as the basis for the new ISO project 23990 Underwater

Acoustics—Bioacoustical Terminology via the SATURN

terminology standard.

For passive acoustic processing bands, ADEON adopted inter­

national standard decidecade band terminology (IEC 61260-

1:2014) whereby multiple decidecade bands can be combined

into a single decade band or user selected bands (https://doi.

org/10.6084/m9.figshare.6792359.v2). To achieve high frequency

resolution over a wide frequency range, the ADEON Data

Processing Specification (https://doi.org/10.6084/m9.​figshare.​

12412610.v1) introduced hybrid millidecade bands, with mil­

lidecade bands used at high frequency and 1 Hz bands at low

frequency (Martin et  al., 2021). Finally, two further standards

describe ADEON’s choice of hardware (https://doi.org/​10.6084/

m9.figshare.6809711) and calibration and deployment guidelines

(https://doi.org/10.6084/m9.figshare.6793745).

ADEON RESULTS

Passive Acoustics

A total of 116 TB of passive acoustic data were recorded during

the three-year data collection phase of ADEON. All data were

retrieved, except for August–November of 2019 and 2020 at site

VAC, which were lost due to commercial trawling; these land­

ers were successfully retrieved thanks to their satellite beacons

(Figure 1). Figure 2 summarizes this extensive dataset using

the monthly empirical probability density functions (EPDF) of

the one-minute sound pressure levels (SPL) in various decide­

cade frequency bands. The broadband SPL was computed from

the high-frequency sampling rate data and covers four ADEON

decade bands, which are sum of the decide­

cade bands centered from 10 Hz to 80,000 Hz,

with edge frequencies of 8.91–89,100 Hz. The

peak of the EPDFs for the broadband SPL at

all stations was near 100 dB re 1 µPa². The

two stations closest to shipping lanes (VAC

and HAT) had the highest peak SPLs in their

broadband EPDFs.

The EPDFs for four decidecade bands

shown in Figure 2 present some of the key

features of the OCS soundscape. The 20 Hz

decidecade band had higher levels in win­

ter than in summer due the mating cho­

rus of fin whales, showing that this biologi­

cal contribution is often the most notable part

of the soundscape at 20 Hz. The 20 Hz and

125  Hz decidecade bands at CHB had dis­

torted EPDFs due to the strong effect of flow-​

induced noise on the results. In general, the

125 Hz decidecade band exhibited substantial

contributions from two sources—vessels and

minke whales. The differences between the

summer and winter sound levels at the south­

ern stations (WIL, CHB, SAV, JAX, and BLE)

were caused by the mating chorus of minke

whales in winter. The two northern stations

(VAC and HAT) showed little difference

between summer and winter months due

to the frequent presence of vessels. The two

higher frequency decidecade bands (630 Hz

and 3,150 Hz) both show higher SPLs in

winter and lower levels in summer, associ­

ated with higher mean wind speeds in winter

than in summer.

Several studies of the ADEON soundscape

have provided insight into the contributions

FIGURE 2. An overview of the ADEON soundscape using monthly empiri­

cal probability density functions of one-minute sound pressure levels aver­

aged over all years. The columns are different frequency bands: broadband

(8.91–89,100 Hz) sound pressure level (in dB), and the 20, 125, 630, and 3,150 Hz

decidecade bands. The seven rows are for the seven recording locations. The

colors represent the month, as shown by the legend on the right. A dashed line

at 90 dB provides a reference for comparison between frequency bands and

stations. At VAC, the lander was picked up by fishers in July of 2019 and 2020,

so only data from 2018 are available for August to November. The reference

sound pressure is 1 µPa.

June 2025 | Oceanography

45

of various sources and explored different approaches to quanti­

fying their effects. The detections of vessels (Figure 3) differed

significantly between stations. HAT and JAX, which were closer

to shipping lanes, had higher daily counts than the other loca­

tions. Detections at HAT were reduced in the second year due to

masking by high overall sound levels.

The ADEON data were employed to develop a soundscape

code (Wilford et  al., 2021), which was subsequently used to

explore the differences between ADEON sites with (SAV) and

without (BLE, WIL) live hard bottom deep-water coral and a

tropical coral reef. The tropical coral reef was unique to the

deep-water sites; however, the two deep-water coral reefs (one

from ADEON and one from ADEON’s sister NOPP project,

DeepSearch) were also different from the sites without live hard

bottom, indicating that soundscape metrics can distinguish

these deep-water habitats (Wilford et al., 2023).

The 2019 and 2020 ADEON data were studied to determine

if there were differences in the soundscape associated with the

global COVID shutdown in March 2020. Changes in sound lev­

els that were detected in this offshore region did not align with

the shutdown period (Miksis-Olds et al., 2022).

Kowarski et al. (2022) examined the presence of cetaceans in

the ADEON area. A total of eight odontocete and six mysticete

cetacean species/groups were identified in the ADEON data.

There was higher species diversity during winter months than

summer months, suggesting that species were moving north in

the summer and south in the winter. Dolphins were the most

commonly detected species group, with presence at all stations

in all months. BLE and SAV were identified for the first time

as sites with regular presence of beaked whales that exhibited

species-​specific site fidelity. Blainsville’s beaked whales were

present in most months at BLE, while SAV

had either True’s or Gervais beaked whales

present in most months. North Atlantic

right whales were only confirmed on one

occasion, in January 2018 at HAT. For the

other mysticete species, ADEON con­

firmed results first reported in Davis et al.

(2020) that the distribution of blue and sei

whales is moving northward, and that sei,

blue, and fin whales are using the deeper

waters of the OCS more than previously

reported. Minke whales were highly vocal

at the southern and offshore ADEON sites

in the winter months, which confirmed

the proposal by Risch et  al. (2014) that

the OCS is an important mating ground

for minke whales. Kiehbadroudinezhad

et al. (2021) developed a new detector for

minke whales’ pulse trains and proposed

a new method for relative abundance esti­

mation to compare the presence of minke

whales in space and time using the ADEON data. Continued

acoustic ocean monitoring is important to document further

shifts and potential human-cetacean interactions in the future.

Active Acoustics

Pelagic zooplankton and fish distributions are spatially and tem­

porally patchy, requiring large amounts of data to fully cap­

ture their variability (Mackas et al., 1985). This makes estimat­

ing pelagic population abundances difficult, expensive, and time

consuming. Scientific echosounders historically deployed from

vessels are efficient for acquiring temporal and spatial data to

characterize the physical properties of the water columns that

pelagic organisms occupy (e.g., internal waves) (Benoit-Bird and

Lawson, 2016). Technological advances have resulted in auton­

omous systems that can be deployed on moorings or landers to

collect time series of longer duration than ship-based sampling,

though at a single location (Trevorrow, 2005). Multiple station­

ary systems spread across a region of interest can provide infor­

mation at broader spatial scales; however, the spacing of these

systems depends on the intrinsic biological and physical pro­

cesses present. The ADEON team objectives focused on biologi­

cal scatter in the water column, and it is hoped that the publicly

available data will inspire future research focused on the physi­

cal parameters linked to the backscatter signals.

The ADEON program incorporated both bottom-deployed

upward-looking and vessel-based downward-looking active

acoustic data collection and biological net tows (Figure 4a) to

provide information relevant to the placement of the stationary

AZFP sampling systems operating at 38, 125, 200, and 455 kHz.

Blair et al. (2021) describe FSASs measuring 38 kHz backscat­

ter from a vessel (Figure 4b) over an area of 100 km2 (Figure 4c)

FIGURE 3. Average number of vessel closest points of approach (CPAs) are

shown as detected at ADEON stations by month for the second and third

monitoring years.

Oceanography | Vol. 38, No. 2

46

centered at the seven ADEON bottom lander sites during a

three-year period. Volume backscatter data were gridded both

horizontally (100 m) and vertically (5 m; Figure 4c) to produce

variogram range estimates, the distance over which data are spa­

tially autocorrelated, providing a proxy for scatterer patch size

and representative distance (Legendre and Fortin, 1989). Patch

horizontal lengths were consistently 2–4 km among the seven

ADEON locations (Blair et al., 2021).

A second study compared the spatial and temporal autocor­

relations of vessel survey and stationary backscatter data using

two approaches. First, virtual backscatter transects were cre­

ated by advecting stationary echosounder data using measured

current velocities from the vessel-mounted acoustic Doppler

current profiler during the FSASs at each site. This was done

during the same night an FSAS occurred, so spatial autocorrela­

tion could be estimated for both data types. Next, the tempo­

ral autocorrelation of the two-week-long time series of hourly

backscatter (Figure 4d,e) centered in time on each applicable

FSAS date for three sites (VAC, HAT, and JAX) was converted

into a distance estimate to compare with the FSAS variogram

ranges (Figure 4e). This methodology allowed for longer time

periods (up to two weeks instead of 12 hours) to be analyzed

and for associated autocorrelation patterns to be detected. The

resulting autocorrelation distances from the stationary systems

(0.8–3.4 km) were similar to those (1.3–3.8 km) from vertically

integrated FSAS data from the same three sites (Blair, 2023).

The spatial characteristics of epi- and mesopelagic scattering

layers are rarely measured in the horizontal dimension, yet they

are imperative information for the design and implementation

of monitoring and management programs for pelagic ecosys­

tems (Horne and Jacques, 2018). These findings demonstrate the

importance of considering scale when designing active acoustics

monitoring networks and sampling protocols. Comparing scales

of space and time in the dynamic ocean is a nontrivial task, and

it remains unknown whether the characteristics measured along

the US eastern continental shelf are representative of shelf-slope

environments in other regions.

Acoustic Propagation Modeling

Soundscape modeling is among a number of considerations used

for policy decisions related to ocean sound. It is important to

know the performance accuracy of soundscape models (Heaney

et al., 2024), and measurements from the ADEON project are

extremely valuable for this purpose. For the acoustic modeling

component of ADEON, a wind and shipping soundscape model

was developed for the Atlantic OCS. This permitted evaluation of

the spatial and temporal distributions of the soundscape beyond

the data collected at the lander locations. Acoustic propagation in

the ocean is sensitive to temperature and salinity fields, bathyme­

try, seafloor sediment type, and sea surface roughness (a function

of wind speed) (Jensen et al., 2011). The soundscape modeling

approach consisted of three steps: (1) identify the distributions of

sources contributing to sound in the region and collect the rele­

vant environmental information, (2) compute the acoustic prop­

agation loss from all sources to all receiver positions, and (3) sum

the contributions and compute the SPL.

The regional SPL was computed for the years 2018, 2019,

and 2020 for decidecade bands centered at 20, 50, 100, 200, and

400 Hz. A single snapshot and a monthly average of the SPL

for 50 Hz at the seafloor is shown in Figure 5 panels a and b,

respectively. The temporal observation window was three hours

for 2018 and 2020 and 10 minutes for 2019. The 2019 model

was generated first, and the 10-minute temporal observation

window proved computationally expensive with an extensive

storage requirement; thus, the observation windows for 2018

and 2020 were expanded to three hours. This massive model­

ing product dataset is served to the public on the ADEON web­

site (https://ADEON.unh.edu) as explained in the visualiza­

tion section below. One observation of this modeling study was

that the SPL on the seafloor was often 3 dB higher than that at

10 m depth, due to the downward refraction of shipping sound

(Heaney et al., 2024).

The wind and shipping sound levels for each of the lander

positions were computed with a higher resolution time obser­

vation window of five minutes. Sediment uncertainty, oceano­

graphic variability, and shipping source depth and level uncer­

tainties were incorporated using a Monte Carlo framework. The

sediment uncertainty drives the modeled SPL, permitting an

estimate of the local sediment characteristics when compared

with the observed data. Figure 5c shows the modeled 125 Hz

decidecade band SPL (5th, 50th, and 95th percentiles) along

with the measurements for the WIL site for the first week of

January 2019. The percentiles relate to the weekly mean SPL dis­

tribution across the sediment types. The data match the 5th per­

centile model across the ensemble with only a few passing ships

above the wind noise floor. The comparison of the SPLs using

the best sediment value for BLE (sediment grain size parame­

ter, phi = 5.68) is shown in Figure 5d. The short time duration

peaks are nearby passing surface ships, and the slowly varying

low SPL regions are wind levels. The differences between the

two sites can be attributed to the number of passing ships and

the sediment (WIL having more ships and sediment with higher

acoustic impedance, and BLE having both fewer ships and lower

impedance sediment).

Ecosystem Modeling

The ADEON ecological modeling component focused first on

describing the temporal abundance patterns of marine mam­

mals across the entire study region (Figure 6a). This informa­

tion was then used to quantify the variability in marine mammal

distribution via call density as it related to changing oceano­

graphic conditions. Both the diversity in calling marine mam­

mals as well as the species-specific detection rates were analyzed

concurrent with the lander and remotely sensed oceanographic

June 2025 | Oceanography

47

parameters. Predictive models were built using species-specific

call density as the response variable to identify persistent areas

of high trophic transfer or biodiversity in the ADEON study

site (Figure 6b). Ongoing analysis is examining how changes

in abundance and distribution of the forage assemblage var­

ies relative to warm/poor and cool/good productivity years off

the US East Coast using taxon-specific community assemblage

metrics from the lander multi-frequency echosounder systems

(Figure 6c). These data can be used to examine regional and

seasonal differences in marine mammal species-environment

relationships. Subsequently, estimates of the acoustic commu­

nity structure, for example, time series of different size classes

FIGURE 4. Net tows collected samples of the fish and zooplankton at each site. (a) Top row: flatfish larva, adult myctophid, siphonophore, salps. Bottom

row: copepod, krill, amphipod, pteropod. Aggregations of these animals in the water column are visible as backscattering layers in echograms of acous­

tic transects. (b) Fine-scale acoustic surveys (FSASs) measured biological backscatter data in a grid of parallel transects covering an area up to 100 km2

centered on the lander location. (c) Spatial heterogeneity was assessed using the nautical area scattering coefficient (NASC, an acoustic measure pro­

portionate to biomass; NASC = 4 pi × 18,522 × area backscattering coefficient in m2/nmi2), integrated as cells 100 m across and 5 m deep (b,c: Blair et al.,

2021). The example transect (b) and FSAS 5 m depth layers (c) were collected at the CHB site the night of December 4, 2017 (UTC). (d) Stationary back­

scatter collected at VAC, HAT, and JAX landers (example echogram is two days at hourly resolution from HAT) were compared to FSASs for the two-

week period centered in time on that FSAS date. (e) The two-week time series (black line) was decomposed to the underlying trend component (red

line) for which the partial autocorrelation function (PACF) was calculated (inset). The autoregressive process order defining the temporal autocorrelation

of the time series (inset, green line) was divided by the mean current velocity collected during FSASs surrounding the stationary echosounder location

to calculate a distance estimate that could be compared with FSAS spatial autocorrelation estimates.

Oceanography | Vol. 38, No. 2

48

from acoustic backscatter data, can be compared to the ecolog­

ical modeling results to gain a better understanding of the rela­

tionship between potential prey species and marine mammal

predators to further enhance the use of acoustic prey data as an

ecological monitoring tool. Acoustically inferred prey commu­

nity structure and biomass, in addition to surface and at-depth

measurements of physical water column features, can be coupled

with acoustic detections of marine mammals to better inform the

fine-scale response of top predators, initiating a more complete

understanding of ecosystem structure and ecosystem changes.

EVOLVING THE ADEON COMMUNITY

The terabytes of acoustic and oceanographic data acquired in

ADEON are valuable in their own right as a baseline charac­

terization of the Mid- and South Atlantic OCS, but their value

will continue to increase through the use of the data in ecolog­

ical and soundscape modeling to support future predictions

and scenarios as environmental conditions change. Innovative

development of online visualization tools to explore ADEON’s

integration of acoustic observations, soundscape modeling,

environmental parameters, visual surveys, and remote sens­

ing (https://adeon.unh.edu/map) promotes the use of ADEON

data beyond the program end. These tools assist in creat­

ing value-added products so that the information is used as

widely as possible.

While all ADEON recordings are publicly available for down­

load, most researchers lack the 116 TB required to store the

audio files, and interested parties may not have access to nor

the training required for using audio analysis software. To aid

researchers and the public in exploring the ADEON datasets,

an integrated suite of web-based visualization tools was cre­

ated. The visualization portal page opens with a map that shows

ADEON lander locations surrounded by marine mammal sight­

ings from the project’s cruises (Figure 7a). Animations that can

be viewed on the main map allow the site visitor to play back

years of soundscape modeling data, showing predicted contri­

butions from wind and AIS-tracked ships. Additional contextual

layers can be displayed that show environmental data collected

from remote satellite sources, such as chlorophyll concentrations

from NASA and surface temperatures from NOAA’s RTOFS

model, to explore meaningful relationships among the parame­

ters. Selecting a lander icon on the map opens an interface with

details on the lander and shows tabs for accessing lander-​specific

data visualizations.

FIGURE 5. (a) Single time snap­

shot of the modeled 125 Hz

decidecade band sound pres­

sure levels (SPL), combined wind

and ship SPL (in dB) at the sea­

floor for the Atlantic OCS for

January 3, 2019. (b) Month aver­

aged 125 Hz decidecade band

SPL (in dB), combined = wind and

ship SPL soundscape model at

the seafloor. (c) Wilmington (WIL)

measured SPL (blue dots) and

5th, 50th, and 95th percentile

modeled SPL for the first week

of January 2019, 125 Hz decide­

cade SPL. (d) Blake Escarpment

(BLE) measured SPL (blue dots)

and modeled SPL with sedi­

ment grain size parameter (PHI)

5.68 for the first week of January

2019, 125 Hz decidecade SPL.

The integer tick marks in (c) and

(d) are at midnight UTC. The time

axis starts at 00:00 on January 1,

2019. The reference sound pres­

sure is 1 µPa.

Instantaneous Seafloor SPL

Mean Seafloor SPL

WIL 125 Hz

BLE 125 Hz PHI:5.68

Sound Pressure Level (dB/µPa2)

Decidecade SPL/dB

June 2025 | Oceanography

49

An important visualization is the tri-level spectrogram, which

presents the acoustic recordings from a lander in an easy-to-use

exploratory interface (Figure 7b). Using a color scale perceptu­

ally optimized to highlight marine mammal sounds, spectro­

grams are pre-processed into image files sufficiently compressed

to be loaded faster than users can scroll, allowing for seamless

exploration. The top level of the spectrogram viewer displays

weeks to months of audio (depending on monitor resolution)

and allows users to quickly peruse the entire dataset, see trends,

and spot major events. The middle level shows roughly a day of

spectrogram data, while the bottom level shows a few minutes

at full resolution. The levels are linked, so clicking on one level

centers the other levels around the same time. Selections can be

made in the lower-level view, allowing in-browser playback or

download of sound files from specific time ranges, with options

to select and filter by frequency.

An event viewer presents marine mammal detections in

an interactive heatmap (Figure 7c). Users select an event type

(e.g., dolphin click) and view a plot of detected events over the

entire project duration. Alternatively, all years can be stacked

to produce a cyclic visualization that reveals repeated seasonal

patterns, with an option to interactively emphasize contribu­

tions from each year. The heatmap can be shifted in direction to

center patterns. Clicking on individual heatmap cells switches

over to the spectrogram viewer, which jumps to the correlating

timestamp. Additional context is provided via a day/night indi­

cator band and environmental data plots (e.g., chlorophyll). A

second lander can be selected to perform direct comparisons

within a single heatmap (using multiple colors).

Finally, the deviations viewer presents a similar tri-level

interface, but instead of spectrograms, it displays times and fre­

quency ranges in which the soundscape was unusually loud or

quiet, based on a weekly, monthly, or quarterly moving win­

dow analysis (Figure 7d). For the data displayed in the viewer,

recordings were processed into 60-second, decidecade fre­

quency bins. Running means and standard deviations were cal­

culated for each window length, and the number of standard

deviations above or below the running mean was mapped to a

diverging blue-white-red heatmap. See Butkiewicz et al. (2021)

for additional details. Since project completion, the visualiza­

tion interface has been successfully used by the public as indi­

cated by the project webpage visitor log, and it provides a valu­

able tool to other researchers for studying a wide range of topics

from marine mammal behavior to extracting training data for

AI/ML detection applications.

SUMMARY

The ADEON team designed and deployed an ocean acous­

tics observation network on the US OCS between Virginia

and Florida from November 2017 to December 2020. The

10

20

30

40

50

11/11/17

12/11/17

1/10/18

2/9/18

3/11/18

4/10/18

5/10/18

6/9/18

7/9/18

8/8/18

9/7/18

10/7/18

11/6/18

12/6/18

NASC (m2 nmi–2)

HAT NRS Med (125 kHz)

HAT NRS Large (125 kHz)

HAT RS Small (38 kHz)

HAT RS Large (38 kHz)

DISTRIBUTIONAL AND

BEHAVIORAL DATA

Presence/absence of prey from active

acoustics and predator from passive

acoustics and sightings

OCEANOGRAPHIC DATA

Sea surface temperature and

chlorophyll from satellite measurements

ENSEMBLE MODELS

Generalized additive

mixed models,

boosted regression

trees, Bayesian

approaches

SPATIAL AND

TEMPORAL PREDICTIONS

Probability of occurrence of mid-trophics

and top predators, time series of

abundance of mid-trophics and

top predators

FIGURE 6. (a) Ecosystem modeling framework. (b) Example of a daily spatial prediction of relative fin whale

call density on September 7, 2018, using preliminary fitted relationships from a generalized additive model.

(c) Acoustic backscatter can be apportioned to different taxonomic or size classes of scatterers (i.e., NRS

and RS, non-resonant and resonant scatterers respectively; medium NRS at 125 kHz [10–25 mm], large NRS

at 125 kHz [25–122 mm], small RS at 38 kHz indicative of small swim-bladdered fish, and large RS at 38 kHz

indicative of larger swim-bladdered fish based on animal total length; Miksis-Olds et al., 2021). These param­

eters (representing the abundance or biomass of different types of zooplankton or fish) can then be used as

model input parameters to determine relationships between prey abundance and marine mammal predator

presence or vocal behavior. These are the time series of size classes from the HAT lander.

74°W

40°N

38°N

36°N

34°N

32°N

30°N

28°N

82°W

78°W

80°W

76°W

Fin

Activity

10

Oceanography | Vol. 38, No. 2

50

multi-platform network acquired soundscape, acoustic back­

scatter, oceanographic, and space-based remote sensing data

that supported high-resolution time series analysis, soundscape

modeling, and ecological modeling to better understand eco­

system dynamics and human use in an under-sampled region.

The development of the ALTO lander during the ADEON pro­

gram has successfully demonstrated its utility for transloca­

tion to numerous other national and international monitoring

efforts. ADEON standardization and visualization products are

now being used globally to explore and compare acoustic data­

sets acquired in different geographical regions and with different

hardware systems. Our results indicated that marine mammal

use of the OCS is more complex than previously documented.

Beaked whale species were observed to exhibit site fidelity along

the OCS, and the offshore area of the Blake Plateau was iden­

tified as a hotspot for minke whales during the mating season.

Advances in soundscape modeling illustrated that the presence

of individual ships significantly impacts the measured and mod­

eled soundscape across the OCS and that acoustic energy is

greater at the seafloor compared to the surface in the ADEON

region. Continuous measures of predator foraging activity and

prey biomass and distribution across multiple years is rare out­

side of a coastal setting and has proven valuable for predic­

tive modeling of predator presence in changing environmen­

tal conditions. Lastly, the partnerships established during the

ADEON program, including the artist-at-sea program, posi­

tive interactions with commercial fisherman, and collabora­

tion with the Ocean Tracking Network and NOAA’s National

Centers for Environmental Information (NCEI), continue to

highlight the value of ocean acoustics, marine science, and sci­

entific research to society.

FIGURE 7. The ADEON visualization suite allows users to explore the overlap of regional acoustic measurements, modeling, and remote

sensing. (a) Main map interface, showing ADEON regional area, modeled ship noise contribution to soundscape, lander locations, and

probe interface windows opened for two landers. Users can select from multiple environmental overlays in the interface window. (b) Tri-level

spectrogram viewer interface showing an approximate week (top), day (middle), and hour (bottom). The different time scales highlight spe­

cific sources contributing to the soundscape. A vessel passage is captured in the day scale, and a selected whale call is highlighted at the

hourly level for user playback and download. (c) Event detection heatmap interface, showing cyclic visualization of dolphin click events over

multiple years stacked on top of each other, with a concentration during the nighttime hours, and contributions from a single year high­

lighted. The colored sea surface temperature (SST) data are time aligned with the marine mammal detections. (d) Deviations viewer, show­

ing times and frequency ranges where it was unusually quiet or loud based on analysis by adjustable-duration moving window.

June 2025 | Oceanography

51

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10.0022514.

ACKNOWLEDGMENTS

We gratefully acknowledge funding provided by the US Department of the Interior,

Bureau of Ocean Energy Management, Environmental Studies Program under con­

tract Number M16PC00003, in partnership with other NOPP funding agencies.

Funding for ship time was provided under separate contracts by ONR, Code 32.

Thanks to all of the ADEON team at JASCO who contributed to the fieldwork and

analysis over the program lifetime. Carmen Lawrence and Jack Hennessey contrib­

uted to Figure 1. Colleen Wilson assisted with Figure 2 and Figure 3. This program

would not have been possible without the dedicated support of John Macri (UNH),

Terry Ridgeway (UNH), Tim Moore (FAU), Ilya Atkin (UNH), and the many students,

volunteers, ROV Jason crew, and captains/vessel crews of R/V Neil Armstrong

and R/V Endeavor.

AUTHORS

Jennifer L. Miksis-Olds (j.miksisolds@unh.edu), Center for Acoustics Research &

Education, University of New Hampshire, Durham, NH, USA. Michael A. Ainslie,

JASCO Applied Sciences (Deutschland) GmbH, Germany. Hannah B. Blair,

Department of Natural Resources and the Environment, Cornell University, Ithaca,

NY, USA. Thomas Butkiewicz, Data Visualization Research Lab, Center for

Coastal and Ocean Mapping, University of New Hampshire, Durham, NH, USA.

Elliott L. Hazen, Ecosystem Science Division, Southwest Fisheries Science Center,

NOAA, Monterey, CA, USA. Kevin D. Heaney, Applied Ocean Sciences, Fairfax

Station, VA, USA. Anthony P. Lyons, Center for Coastal and Ocean Mapping and

Center for Acoustics Research and Education, University of New Hampshire,

Durham, NH, USA. Bruce S. Martin, Applied Research (Canada), Dartmouth, NS,

Canada. Joseph D. Warren, School of Marine and Atmospheric Sciences, Stony

Brook University, Southampton, NY, USA.

ARTICLE CITATION

Miksis-Olds, J.L., M.A. Ainslie, H.B. Blair, T. Butkiewicz, E.L. Hazen, K.D. Heaney,

A.P. Lyons, B.S. Martin, and J.D. Warren. 2025. Overview of the Atlantic Deepwater

Ecosystem Observatory Network. Oceanography 38(2):40–51, https://doi.org/​

10.5670/oceanog.2025.301.

COPYRIGHT & USAGE

This is an open access article made available under the terms of the Creative

Commons Attribution 4.0 International License (https://creativecommons.org/

licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and repro­

duction in any medium or format as long as users cite the materials appropriately,

provide a link to the Creative Commons license, and indicate the changes that

were made to the original content.

Oceanography | Vol. 38, No. 2

52

FEATURE ARTICLE

EXPLORING CLIMATE CHANGE, GEOPOLITICS, MARINE

ARCHEOLOGY, AND ECOLOGY IN THE ARCTIC OCEAN THROUGH

WOOD-BORING BIVALVES

By Jørgen Berge, Torkild Bakken, Kristin Heggland, Jon-Arne Sneli, Øyvind Ødegård, Mats Ingulstad,

Terje Thun, and Geir Johnsen

BACKGROUND

In 1652, a young Siberian larch sprouted somewhere along the

Yenisei region in Siberia (Figure 1). Almost 250 years later, in

1904, that tree died. Then, in 2016, it ended up in a bottom trawl

in the Arctic Archipelago of Svalbard. In order to reach Svalbard,

the log must have been captured by sea ice in the Kara Sea and

transported by the Transpolar Drift (TPD) across the Arctic

Ocean before it was released and eventually sank in Rijpfjorden

at 80°N. When it was brought up on the deck of the research

vessel and examined by scientists, the log was heavily infested

with living specimens of the wood-boring bivalve Xyloredo nooi.

Shipworms and other wood-boring mollusks have never before

been reported from the High Arctic. This is, however, not only

a story about a piece of wood drifting across the Arctic Ocean

and the first report of Arctic wood-boring mollusks. It also tells

a story about the connection between climate and environmen­

tal conditions, and the history of human activity in Svalbard, the

influence of the European timber industry and the Soviet Union

planned economy, Arctic resource extraction during the last

400 years, and preservation of marine archeological artifacts—

and it reveals significant gaps in knowledge concerning Arctic

benthic fauna. The latter has strong implications for contem­

porary geopolitical issues in the region, including the ongoing

debate regarding deep-sea mining.

MATERIALS AND METHODS

During two research cruises on R/V Helmer Hanssen funded by

The University of Tromsø – The Arctic University of Norway

(UiT), pieces of wood infested with wood-boring mollusks

were trapped and collected in the bottom trawl (Campelen

1800 bottom trawl) at two locations on Svalbard. In January

2016, a 7 m long log that was partly buried in anoxic sedi­

ment was collected in Rijpfjorden, located on the northern side

of Nordaustlandet, Svalbard. (80°17'40.44''N, 22°18'0.07''E) at

250 m depth. A second piece of infested wood was collected on

June 26, 2019, on the west coast of Svalbard in Smeerenburgfjord

at 215 m depth.

Wood-boring mollusks collected from the wood were

brought back to the laboratory and identified following origi­

nal descriptions of Xyloredo species (Turner, 1972). The col­

lected specimens were found to comply with the description

of X. ingolfia and deposited in the collections at the Norwegian

University of Science and Technology Museum in Trondheim

(NTNU-VM 82062-82067; Bakken et  al., 2024). In order to

undertake a thorough taxonomical identification, type speci­

mens (paratypes) of X. ingolfia were borrowed from the Natural

History Museum of Denmark in Copenhagen (NHMD-76456).

The newly collected mollusks were similar to the type spec­

imens in proportion of valves and in the sub-rectangular and

ABSTRACT. We present the first record of a wood-boring, deep-sea mollusk belonging to the genus Xyloredo from the high Arctic.

Wood-boring mollusks of the genus Teredo have previously sporadically been documented in the Arctic, but only in shallow waters

strongly affected by relative warm Atlantic waters. Our finding not only identifies a new and until now unknown member of the

Arctic marine bottom fauna but also points to the fact that historical shipwrecks in the region may not be as well preserved as we

thought. Further, this study demonstrates how the natural and cultural histories of the Arctic are deeply intertwined, necessitating

interdisciplinary approaches to uncover connections and insights across domains that might otherwise remain obscure. Specifically,

we demonstrate how the discovery of wood-boring mollusks, inside a Siberian larch that sprouted in the Yenisei region in 1652 and

recovered in a bottom trawl offshore Svalbard, is directly linked to the Transpolar Drift. Analyzing how a tree ends up in a Svalbard

fjord more than 100 years after its death in 1904 also provides insights into how the logging industry in Siberia has significantly influ­

enced human presence on and the history of Svalbard. Without extensive logging in Siberia, far less driftwood would have reached

Svalbard during the last 100 years. Hence, there would have been fewer wood falls to attract the wood-eating bivalves in its ecosys­

tem, and as driftwood has been an important resource for firewood and building materials, Svalbard’s human history would most

likely have been different.

June 2025 | Oceanography

53

well-calcified nature of an accessory plate called a mesoplax

(Turner, 1972, 2002). The morphological examination did not

reveal any difference between the collected specimens from

Rijpfjorden and Smeerenburg. However, X. ingolfia has been

synonymized with X. nooi (Voight, 2022).

Based on dendrochronology and established reference

chronologies from Russian Larix, the tree ring patterns in

the log collected from Rijpfjorden indicate that the tree lived

during the period 1652–1904 in the Yenisei region in Siberia

(Russia). For genus and species identification, methods based on

morphology detailed in Kolar et al. (2022) and Alm (2019) were

used for this study. For the analyses of tree rings, the CATRAS

system (Computer Aided Tree ring Analyses System; see Aniol,

1983) was used. See the online supplementary material for fur­

ther description of this analysis.

RESULTS AND DISCUSSION

Two previous studies (Alm, 2019; Linderholm et al., 2021) con­

cluded that 87% of the driftwood examined from Svalbard con­

sisted of three genera: Pinus (pine), Picea (spruce), and Larix

(larch), with Siberian larch (Larix siberica) as the dominant

species. Although we cannot rule out that it is a different spe­

cies of Larix, we refer here to the specimen as a Siberian larch.

The exact species identification is not a key part of the find­

ings we present, nor of the interpretation of the results. The

Linderholm et  al. (2021) study was carried out in the south­

western part of Spitsbergen, in a region where coastal surface

currents flow northward from the southern tip of Svalbard.

Irrespective of which species this is, there are no trees grow­

ing on Svalbard. Also, surface currents in our study’s part of the

Arctic flow west. Hence, for a log to end up in Rijpfjorden, the

FIGURE 1. Map of the Arctic with sea ice, ocean currents, Transpolar Drift (TPD), and projected drift patterns of Fram, the Siberian larch found in

Rijpfjorden on Nordaustlandet (Svalbard), and an Ice-Tethered Observatory (ITO) deployed at the North Pole in 2022. The white area indicates multiyear

sea ice, and white/blue stripes the seasonal ice zone. Black dots show where USS Jeannette sank in 1881 and where parts of the wreckage were found

in 1884. The green line indicates the suggested route of transport for the Siberian larch found in Rijpfjorden, the purple line indicates the drift trajec­

tory of Fram from 1893 to 1896, and the red line indicates the seven-month drift trajectory of the ITO in 2022. The thick light red arrow at the bottom of

the figure tracks the northward-flowing West Spitsbergen Current that brings warm Atlantic water into the Arctic Ocean, the thick white arrow indicates

the TPD transporting sea ice out into the Fram Strait, and the thick turquoise arrow follows cold Arctic water flowing out of the Arctic Ocean along the

east coast of Greenland. Left inserts, from top to bottom, show part of the log found in Rijpfjorden, a cross section of the log with traces of wood-boring

molluscs and several individuals of X. nooi, and a close-up of two specimens of X. nooi. Right inserts, top to bottom, depict USS Jeannette, Fram frozen

into sea ice, and a forest with Siberian larch.

Oceanography | Vol. 38, No. 2

54

only possible direction of transport is westward via the TPD

(Figure 1). Thus, driftwood in Rijpfjorden will more than likely

originate east of Svalbard.

The Rijpfjorden log was heavily colonized with living spec­

imens of different sizes of the wood-boring mollusk Xyloredo

nooi (Figure 1). Rijpfjorden is a north-facing fjord that has an

annual extended ice cover consistently dominated by Arctic

water masses (Berge et al., 2009). The bottom temperature in

the region remains at –1.8°C throughout the year (Cottier et al.,

2021, 2022). The second record of X. nooi was documented in

the wood recovered from Smeerenburgfjord (Figure 1).

The two Svalbard fjords represent very contrasting oceano­

graphic environments. While the north-facing Rijpfjorden is

characterized by Arctic water masses, Smeerenburg, like other

west-facing fjords on the main island of Spitsbergen, is strongly

influenced by warm Atlantic water (Berge et al., 2005). Although

there are no direct measurements of bottom temperatures in

Smeerenburg, continuous measurements in Kongsfjorden,

another open fjord strongly affected by Atlantic water masses

just south of Smeerenburg, exhibited bottom temperatures rang­

ing between 1.5° and 3.0°C in late June 2009 (Cottier et al., 2021,

2022). As a consequence, the fauna in the two fjords are very dis­

similar, as seen, for example, in the fish fauna (Nahrgang et al.,

2014; Jordà-Molina et al., 2023). Unlike in Rijpfjorden, only frag­

ments of a log were collected in Smeerenburg, and no living spec­

imens (just empty shells) were found. And unlike Rijpfjorden,

Smeerenburg rarely freezes over, as it is strongly influenced by

Atlantic water flowing northward through the Fram Strait, enter­

ing the Arctic northwest of Svalbard (Ingvaldsen et al., 2024).

Driftwood and Wood-Boring Organisms

There are two families of bivalves (Teredinidae and Xylo­

phagaidae) that are able to settle on and digest wood or other

vegetation in the marine environment. As larval stages of species

belonging to these groups undergo metamorphosis, they begin

to bore into and eat the wood in which they settle (Voight, 2015).

Through a molecular phylogenetic study, Distel et  al. (2011)

found the two to be a monophyletic taxon. Many species belong­

ing to the Xylophagaidae are poorly known, and many inhabit the

deep sea. Hence, based on their common ancestry, information

and status about their biology are in many cases only assumed or

deducted, rather than based on detailed biological studies.

The bivalves of the Xylophagaidae occur from a few meters

below low tide to more than 7,000 m depth (Turner 1972, 2002),

boring into wood sunken to the seafloor using toothed ridges

on their anterior shells and ingesting wood fragments (Purchon,

1941). They are considered the sole wood borers at depths

greater than 200 m (Turner, 1972). A wood fall represents a mas­

sive energy input and can be compared to a whale fall on the

seafloor (Ristova, et al., 2017; McClain et al., 2025). However,

the energy in the wood is trapped in cellulose that most organ­

isms are incapable of digesting. To access this energy, bottom

dwellers are dependent on organisms such as X. nooi to digest

the cellulose. In addition, wood-boring mollusks may also con­

tain symbiont bacteria that enable fixation of nitrogen as well as

cellulose digestion (Goodell et al., 2024). By sustaining the wood

fall communities, wood-boring mollusks in the deep sea fill a

role comparable to grazers in the euphotic zone (Turner, 2002;

O’Connor et al., 2014; Voight, 2015).

In the Northeast Atlantic, Xyloredo is represented by X. nooi

known from deep, cold waters and from deep fjord areas

(Turner, 1972; Voight, 2022). A separate undescribed species

was found in widespread localities in the Bay of Biscay and at the

Haakon Mosby Mud Volcano in the northern Norwegian Sea

(Romano et al., 2020). There is no direct evidence confirming

that Xyloredo species specifically release gametes into the water

column for external fertilization. Most research on shipworms

in general (family Teredinidae) suggests that external fertiliza­

tion is a common reproductive strategy, but this has not been

explicitly confirmed for Xyloredo. Given the diversity of repro­

ductive strategies among shipworms, such as brooding larvae

internally in some species, it is possible that Xyloredo exhibits

unique or unstudied reproductive adaptations. Further research

is needed to clarify the reproductive biology of Xyloredo, includ­

ing the mechanisms of gamete release and fertilization.

Because the size and maturity of the specimens found inside

the Rijpfjorden log were distinctly heterogeneous, the demo­

graphic structure of the bivalves indicates either local recruit­

ment and reproduction or multiple recruitment events inside

the fjord. One end of the log carried clear indications of hav­

ing been buried in anoxic sediments, also suggesting that the log

had been partially submerged in Rijpfjorden for several years.

This, and the fact that several juvenile specimens of X. nooi were

found inside the log, strongly suggest local recruitment and/

or reproduction. Although we cannot rule out the possibility

of multiple recruitment events while the log was moving, this

cannot explain the presence of juvenile specimens inside the

log after several years in Rijpfjorden. As the reproductive biol­

ogy of Xyloredo species remains uncertain, it is not possible to

unequivocally assess how recruitment might have occurred

in Rijpfjorden. Importantly, however, both possible events (or

a combination of the two) challenge our status of knowledge

regarding the Arctic marine benthic fauna.

Transpolar Drift

For a Siberian larch that grew in the Yenisei region until the

beginning of the last century to end up in a fjord on Svalbard

(Figure 1), the only mode of transport is by the TPD (Häggblom,

1982). In 1884, the Norwegian researcher and explorer Fridtjof

Nansen came across newspaper reports that fragments of the

hull of the steam bark Jeannette had been found on the east

coast of Greenland. He knew that this ship had been frozen

into the sea ice and wrecked off the New Siberian Islands three

years earlier, during an attempt by the US Arctic Expedition

June 2025 | Oceanography

55

to find entry into what was hypothesized to be an ice-free cen­

tral Arctic Ocean. Nansen was inspired by Jeannette’s finding

and the large quantities of driftwood from Siberia found on the

shores of East Greenland, and reports of driftwood found north

of Spitzbergen, and hypothesized that the Arctic Sea ice drifted

westward across the Arctic Ocean from Siberia toward the

Fram Strait. The existence of the TPD was later documented by

Nansen’s Fram expedition in the 1890s (Nansen, 1897), as he set

out to prove that the currents created by the largest Russian riv­

ers emptying into the Arctic Ocean could push a ship across the

North Pole. The TPD as mechanism to move sea ice by a com­

bination of wind and ocean drag has been modeled to explain

oceanographic surface systems in these parts of the Arctic

Ocean (Spall, 2019). The importance of the TPD for the occur­

rence of driftwood on Svalbard has also previously been exam­

ined and documented by Eggertsson (1994). Driftwood can

also archive climate information, and because the wood trans­

ported on or frozen in ice stays afloat for an extended time, it

can be used to trace historical changes in currents and ice con­

ditions (Linderholm et al., 2021). As demonstrated by a set of

ice-tethered observatories (ITO) deployed at the North Pole in

July 2022 (see Figure 1), the speed of the TPD has increased.

Whereas it took Fram, frozen in sea ice, three years to drift

across the Arctic Ocean (Figure 1), it took the ITOs deployed in

June 2022 only seven months to effectively be transported out

into the Fram Strait (Berge et al., 2025).

Geopolitical and Historical Context

Driftwood can be a naturally occurring and renewable resource,

created by trees falling into the water due to erosion of river­

banks and the break-up of ice in the spring. However, the arrival

of human settlements and industry in arctic territories also

impacted the production of driftwood. The larch tree found

in Rijpfjorden started its life shortly after the first Russian set­

tlers arrived on the banks of the Yenisei, and died just as the

Romanov imperial dynasty entered its last turbulent years before

the Russian Revolution (1917). This occurred at a critical junc­

ture in the development of the international timber trade in the

late nineteenth and early twentieth centuries. The forests of cen­

tral Europe no longer seemed inexhaustible because they could

not meet the growing demand for timber from industrialization

and population growth (Lotz, 2015). Thus, the timber industry

frontier moved north and east, and Russia became the world’s

leading timber exporter.

Commercial logging and timber rafting along the Yenisei

River began in the nineteenth century. The abolition of serf­

dom in 1861 had increased labor mobility, and the state also

encouraged settlement in Siberia. But loggers in Siberia strug­

gled to overcome disadvantages such as lack of modern indus­

trial equipment and transportation to the European markets. Ice

conditions are difficult in rivers flowing toward the far north,

and the Kara Sea was also seen as natural barrier. Only after

the Finnish-Swedish explorer Nordenskiöld successfully sailed

to Ob and Yenisei in 1875 did the establishment of commercial

shipping routes seem feasible. Despite oceanographic research

including depth soundings, hydrographic surveys, mapping of

shoals and ice conditions, very few commercial shipments made

it safely across the Kara Sea before 1904.

The outbreak of the Russo-Japanese war in February 1904,

the same year the Siberian larch died along the Yenisei, greatly

changed the strategic importance of the Northern Sea Route (also

known as the Northeast Passage). The Russian Baltic fleet had to

circumnavigate the world before it could reach Japan, only to be

soundly defeated at the Tsushima Strait in 1905. After the war,

Tsar Nicolas II launched the Arctic Ocean Hydrographic expe­

dition (1910–1915) to open the Northern Sea Route as a strate­

gic objective for the state (Kuksin, 1991). As a part of the new

Russian commitment to expand its activities in Arctic waters,

the polar explorer Rusanov sailed to Spitsbergen to take posses­

sion of coal fields and to promote Russian hunting and resource

extraction, thereby strengthening the Russian position in the

ongoing scramble over Svalbard.

After the Russian revolution in 1917, the new Soviet authori­

ties sought to harness the transportation potential of the Yenisei

for trade in bulky commodities (Nielsen and Okhuizen, 2022).

The Soviet industrialization plans and immense appetite for

wood led to intensification of Siberian logging in the 1920s

and 1930s, and at the same time polar navigation techniques

and technology improved. Stalinist forced-tempo industrial­

ization, imported equipment, and skepticism toward Western

approaches to sustainable management made for a massive, if

wasteful, expansion of the Siberian timber industry (Kotchekova,

2024). It has been estimated that up to 50% of the timber was

lost while being rafted on the Yenisei River in the early decades,

providing a considerable source for driftwood in the Arctic

Ocean. Over time, the share of reported losses dropped even as

the transport volume increased, with the peak transport volume

for the Yenisei occurring around 1960 (Hellmann et al., 2015).

By that time, only 2.5% of the logs were reportedly lost during

rafting (Korpachev et al., 2022). The later disintegration and col­

lapse of the Soviet Union also affected the supply of driftwood,

as harvest levels fell during the economic and political turbu­

lence in post-Soviet Russia (Naumov, 2016).

The combination of the TPD and the logging industry in

Siberia has had a significant influence on human presence and

history on Svalbard. Driftwood was an important resource both

for firewood and building materials. Without the extensive log­

ging in Siberia, the total volumes of driftwood reaching Svalbard

would have been far less during the last 100 years. Hence, there

would have been fewer wood falls for the wood-eating bivalves,

and the history of resource extraction on Svalbard would have

been different. Many small cabins built by hunters and trappers

using driftwood from this period still remain and are today pro­

tected as cultural heritage (Reymert and Moen, 2015).

Oceanography | Vol. 38, No. 2

56

Biodiversity and Underwater Cultural Heritage

The Svalbard fjords provide natural laboratories for exploring the

effects of global warming. Fjords on the west coast receive large

quantities of heat energy, organisms, and particles that are trans­

ported northward by the West Spitsbergen Current (e.g., Berge

et al., 2005). Fjords on the northern part of the archipelago are

more influenced by Arctic water masses. Arguably, Rijpfjorden is

among the most extensively studied High Arctic marine ecosys­

tems (e.g., Jordà-Molina, 2023), thought to host a more endemic

Arctic fauna without the influence of boreal species. Finding

Xyloredo nooi both in Rijpfjorden and Smeerenburg shows that

significant knowledge gaps remain regarding biodiversity and

distribution of species that need to be filled before we can ana­

lyze and understand how future warming of the Arctic may influ­

ence and alter biodiversity, ecosystem composition, and eventu­

ally also ecosystem services in the marine Arctic.

Moreover, and due to the fact that investigations of the few

wrecks discovered in cold-water temperatures have shown no

presence of wood-boring mollusks, there has been an assump­

tion that such organisms do not thrive in the High Arctic (Stewart

et al., 1995). With over 1,000 historic shipwrecks estimated to

be in the waters between Greenland and the Svalbard archipel­

ago (Guijarro Garcia et al., 2006), the area could potentially be

a treasure trove of information not only on Svalbard history but

also on 400 years of Europe’s richest maritime history. The pres­

ence of wood-boring bivalves may pose a hitherto unrecognized

threat to this underwater record of centuries of extractive activity

along the Arctic frontier. The newly discovered wreck of Figaro,

a wooden whaling ship that sank in 1908, did not show signif­

icant signs of damage from wood-boring organisms (Mogstad

et al., 2020). Figaro was discovered in Isfjorden on the west coast

of Svalbard ~100 nm south of Smeerenburg (Figure 1; for details

regarding Figaro, see Mogstad et al., 2020). The fact that Figaro

presently is the only investigated historical wreck in the Svalbard

archipelago underscores the profound knowledge gaps related to

the natural and cultural history of the seabed in these areas.

The rate of Arctic warming is to two to four times the global

average (Gerland et al., 2023), which will impact the biological

diversity as we know it today. A likely effect will be to extend

the distribution of boreal species northward. Following this, the

entry of new and more wood-boring organisms to the Arctic

will pose a threat to cultural heritage, as observed in this story.

However, the story and future perspectives may be entirely dif­

ferent for the deep-sea, cold-water species Xyloredo nooi. The

combination of less sea ice and a much-reduced timber indus­

try in Siberia is likely to result in reduced substrate for these spe­

cies. To some extent, this may be partly counteracted by faster

flow of the TPD (Figure 1), reducing the potential time it takes

for a piece of wood to be transported across the Arctic Ocean.

Nevertheless, less wood on the seabed will then reduce the avail­

ability of steppingstones for wood-boring organisms. On the

other hand, more frequent extreme weather events as a result of

global climate change could increase wood input to the ocean.

All of these factors combined, and in the light of the present

knowledge, it is difficult to predict the status and the vulnerabil­

ity of these deep-sea organisms.

SUMMARY AND CONCLUSIONS

The report of wood-boring mollusks in the High Arctic is indic­

ative of a hitherto unknown, but potentially ecologically signif­

icant, element of the Arctic marine biota. Collected in the rela­

tively well-studied fjords of Svalbard, the discovery also points

toward a major gap in knowledge regarding biodiversity and eco­

system composition. Such knowledge gaps are particularly rele­

vant in light of the Norwegian government’s recent decision to

allow exploration and mapping of the seafloor in preparation for

future development of deep-sea mining (Nature, 2024).

Climate change is fundamentally transforming the Arctic.

Half of the summer sea ice has disappeared since the 1980s, and

the rest is projected to be gone within the coming decades (Kim

et al., 2023). The warming extends from the deep ocean to the

upper atmosphere, impacting ocean circulation, weather pat­

terns, ecosystems, and human presence in the region (Gerland

et al., 2023; Nanni et al., 2024). We need to close knowledge gaps

concerning the Arctic biota to understand the present compo­

sition of Arctic benthic organisms and their ecosystems and

to understand and manage changes to these areas. As demon­

strated in this study, the natural and cultural histories of the

Arctic are deeply intertwined, necessitating interdisciplinary

approaches to uncover connections and insights across domains

that might otherwise remain obscure. Climate change coincid­

ing with increased interest from commercial and geopolitical

actors in the region further enhance this need.

SUPPLEMENTARY MATERIALS

The supplementary materials are available online at https://doi.org/10.5670/

oceanog.2025.311.

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ACKNOWLEDGMENTS

The authors are grateful to UiT The Arctic University of Norway for funding the two

research cruises, and to the crew onboard FF Helmer Hanssen for all their help and

assistance. The authors also want to thank the editor and two anonymous reviewers

for providing constructive comments in two rounds of review.

AUTHORS

Jørgen Berge (jorgen.berge@uit.no), UiT The Arctic University of Norway, Faculty

for Bioscience, Fisheries and Economy, Department of Arctic and Marine Biology,

Tromsø, Norway. Torkild Bakken, Department of Natural History, Norwegian

University of Science and Technology (NTNU) University Museum, NTNU,

Trondheim, Norway. Kristin Heggland, UiT The Arctic University of Norway, Faculty

for Bioscience, Fisheries and Economy, Department of Arctic and Marine Biology,

Tromsø, Norway. Jon-Arne Sneli (deceased), Department of Biology, NTNU,

Trondheim, Norway. Øyvind Ødegård, Department of Archaeology and Cultural

History, NTNU University Museum, NTNU, Trondheim, Norway. Mats Ingulstad,

Department of Modern History and Society, NTNU, Trondheim, Norway. Terje Thun,

The National Laboratory for Age Determination, NTNU University Museum,

NTNU, Trondheim, Norway. Geir Johnsen, Department of Biology, NTNU,

Trondheim, Norway, and University Centre in Svalbard, Department of Biology,

Longyearbyen, Norway.

ARTICLE CITATION

Berge, J., T. Bakken, K. Heggland, J.-A. Sneli, Ø. Ødegård, M. Ingulstad,

T. Thun, and G. Johnsen. 2025. Exploring climate change, geopolitics, marine

archeology, and ecology in the Arctic Ocean through wood-boring bivalves.

Oceanography 38(2):52–57, https://doi.org/10.5670/oceanog.2025.311.

COPYRIGHT & USAGE

This is an open access article made available under the terms of the Creative

Commons Attribution 4.0 International License (https://creativecommons.org/

licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and reproduc­

tion in any medium or format as long as users cite the materials appropriately, pro­

vide a link to the Creative Commons license, and indicate the changes that were

made to the original content.

Oceanography | Vol. 38, No. 2

58

MEETING REPORT

COMMUNITY RECOMMENDATIONS ON

BELONGING, ACCESSIBILITY, JUSTICE, EQUITY,

DIVERSITY, AND INCLUSION INITIATIVES

IN OCEAN SCIENCES A TOWN HALL DISCUSSION

By Julien T. Middleton, Sarah Clem, Katherine L. Gallagher, Erin Meyer-Gutbrod, Amadi Afua Sefah-Twerefour,

Margrethe H. Serres, Mona Behl, and James Pierson

INTRODUCTION

Within ocean sciences, a persistent lack of inclusivity neces­

sitates ongoing initiatives to encourage belonging, accessibil­

ity, justice, equity, diversity, and inclusion (BAJEDI; Bernard

and Cooperdock, 2018). Many existing structures and sys­

tems inhibit the full inclusion of minoritized groups, allowing

inequity to persist in the field (Johri et al., 2021; Wang et al.,

2024). Addressing these challenges is crucial to ensure a diverse,

fair, and inclusive academic community and allow holistic ocean

science research (Johnson et al., 2016; Johri et al., 2021).

To aid in addressing this issue, The Oceanography Society

(TOS)’s Justice, Equity, Diversity, and Inclusion (JEDI)

Committee began hosting interactive discussions at Ocean

Sciences Meetings (OSM) in 2022. The 2024 event took the form

of a town hall entitled “Scientific Societies’ Roles in Building

Inclusive Communities.” To facilitate discussion, the town hall

focused on three discussion questions:

• What are some successful models of expanding participation

of minoritized and/or historically marginalized individuals in

ocean and coastal sciences?

• What can be done to make ocean and coastal careers more

accessible?

• How can we build a just and fair scientific and workplace

culture?

During the interactive session, the 40 town hall participants

shared ideas, engaged with peers, and provided anonymous

written feedback on these questions and on topics related to the

mission of the TOS JEDI Committee.

To assess the ongoing efforts of TOS and complement the

in-person discussion, a brief survey was sent to TOS member­

ship before OSM24, made available through QR codes to all

OSM24 attendees, and is available in the online supplementary

materials. The 13-question survey invited participants to share

their lived experiences surrounding bias, discrimination, and

perception of changes in the BAJEDI landscape in recent years.

Survey participants provided optional demographic informa­

tion. Write-in options were available for all demographic ques­

tions. Identifying information was not collected during the town

hall, and survey responses were fully anonymized to facilitate

participants expressing themselves freely. Here, we summarize

the responses received from the community and highlight the

use of community feedback to direct scientific societies, like

TOS, toward effective approaches for broadening participation

in ocean sciences.

ABSTRACT. During the 2024 Ocean Sciences Meeting (OSM24), The Oceanography Society’s Justice, Equity, Diversity, and

Inclusion Committee hosted a town hall on “Scientific Societies’ Roles in Building Inclusive Communities.” The town hall aimed to

assess ongoing efforts to improve belonging, accessibility, justice, equity, diversity, and inclusion (BAJEDI) within ocean sciences,

promote community building and discussions surrounding BAJEDI topics, and highlight the role of scientific societies in equity

efforts. Here, we summarize the resultant communal discussions, which focused on effective models for increasing participation

in ocean sciences, how to make ocean science careers more accessible, and strategies to build a more equitable community culture.

Discussions highlighted several professional societies working to increase BAJEDI within the field and offered tangible action items

to increase accessibility and equity at all career stages. An optional survey was distributed to OSM24 attendees to assess their lived

experiences. Survey results highlighted that although knowledge of BAJEDI issues and training opportunities have increased, bully­

ing and discrimination are still common. We recommend action items, including increased standardization and public accessibility

of demographic data, to continue improving BAJEDI within ocean sciences.

June 2025 | Oceanography

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RESULTS AND DISCUSSION

Demographics of Survey Participants

and Categorization for Analysis

The 2024 survey had 96 respondents, reflecting a 153% increase

in response rate from a similar TOS JEDI survey carried out

during OSM22 (Meyer-Gutbrod et al., 2023). While consider­

ing the survey results, it is important to acknowledge that survey

respondents and town hall attendees represent a self-​selecting

sub-population of the larger ocean sciences population. The

OSM partner societies collected limited information on attend­

ees. While the OSM24 demographic questions were more lim­

ited in scope than the optional demographic information col­

lected as a part of the TOS JEDI survey, the self-reported gender

of attendees shows that women and gender non-conforming

individuals were overrepresented in the TOS JEDI survey popu­

lation (60% and 3%, respectively) compared to the overall con­

ference population (46% and 1%, respectively). Comparing the

survey respondents’ career stages to overall OSM24 attendee

career stages, graduate students were similarly represented

(28% and 26%, respectively) and retirees/emeritus individu­

als were overrepresented (3% and 17%, respectively). All other

career stages were underrepresented in the survey respondent

group compared to the overall OSM24 attendee population:

undergraduates (1% and 6%, respectively) and early to late

career (54% and 67%, respectively). Generally, consistent col­

lection of demographic information with uniform categories

across institutions and professional societies will allow greater

ability to assess equity efforts (Sturm, 2006; Hughes et al., 2022).

Without this information, it is difficult to build robust, data-

based metrics of success.

Responses to the survey were broken down into three

groups based on self-reported, optional demographic infor­

mation: minoritized individuals (54 respondents), heterosex­

ual white women (19 respondents), and heterosexual white

men (20 respondents). Three respondents who did not wish

to provide demographic data were removed from this analy­

sis. The survey used inclusive descriptions of men and women,

and these categories may include cisgender, transgender, and

gender-​expansive individuals. A write-in option allowed trans­

gender and gender expansive individuals who did not wish to

be grouped in the binary “women” and “men” categories to self-​

describe their gender. All individuals falling outside of hetero­

sexual white women and heterosexual white men are considered

within the minoritized individuals category (i.e.,  non-white,

non-heterosexual, and/or self-​reported as belonging to a gender

minority). Survey results were grouped based on these demo­

graphic delineations for two reasons. First, as the historically

hegemonic group within Western academia, heterosexual white

men are known to be less frequently exposed to prejudice and

have fewer firsthand experiences with prejudice and discrimina­

tion (Liao et al., 2016). Second, while there has been an appre­

ciable increase in equity and inclusivity for heterosexual white

women in the geosciences over the past 40 years, minoritized

individuals have not experienced a similar benefit over the same

period (Bernard and Cooperdock, 2018). This is not to say that

heterosexual white women do not still face significant barriers

in academia, only that the barriers impacting individuals in this

group compared to barriers experienced by minoritized indi­

viduals may differ significantly. Throughout this work, we use

the terminology of Douglas et al. (2022), in which marginalized

refers to a group that is devalued based on demographic identity,

while minoritized refers to the negative experiences of under­

represented groups. Within this framework, heterosexual white

women may experience marginalization, although they are not a

strongly minoritized group in ocean sciences as a whole. As our

limited survey population did not allow for a breakdown of spe­

cific minoritized groups, we present an aggregated analysis to

maintain respondent anonymity.

Survey Responses: Perceptions of

BAJEDI in the Ocean Sciences

Survey questions 1 and 2 asked participants about their personal

experience with bias, discrimination, and bullying within ocean

sciences in the past two years. Most respondents had personally

witnessed bias, discrimination, or bullying (58%, Figure 1a), and

38% of respondents had personally experienced such behavior

over the same period (Figure 1b). Demographic composition at

each career stage shows that survey participants in minoritized

groups are currently underrepresented at higher career stages

(Figure 2a). Of our survey respondents, 46% of minoritized

individuals were graduate students. This declines at each stage,

with minoritized individuals composing only 11% of late career

and 7% of retired and emeritus faculty. Heterosexual white men

showed the opposite trend, with 5% of this group at the early

career stage increasing to 25% and 50% at the late career and

FIGURE 1. Whole population responses

from questions 1 and 2 regarding per­

sonal experiences and observations of

bias, discrimination, and bullying within

ocean sciences in the past two years in

The Oceanography Society 2024 Ocean

Sciences survey.

Oceanography | Vol. 38, No. 2

60

retired/emeritus stages, respectively. Heterosexual white women

show a largely normal distribution over the career stages, with

the mid-career stage covering the largest period of an individ­

ual’s career. As OSM24 collected aggregated data that did not

distinguish early, mid, and late career, it is difficult to compare

these distributions with the overall distribution of career stages

at OSM24. Therefore, assessing whether these distributions indi­

cate personal perceptions within each group as to when BAJEDI

work is most “valuable” professionally is outside the scope of

this study. While the increased representation of minoritized

individuals at the graduate and early-career stages is encour­

aging, a longitudinal analysis between 2007 and 2021 examin­

ing 55 ocean sciences graduate programs in the United States

showed that while the recruitment of minoritized individuals

into graduate programs has increased substantially, the gradu­

ation rate for this group has not concurrently increased (Lewis

et al., 2023). Structural equity, which refers to the intentional

design of institutional policies to minimize systemic bias and

incentivize equity work, is necessary to remove existing barri­

ers to the long-term retention of historically minoritized groups

in ocean sciences. Specific examples of structural equity include

funding first-year graduate fellowships accessible specifically

to minoritized groups (as is common for first-year fellowships

for women), requiring anti-bias training for advising faculty,

considering faculty contributions to BAJEDI initiatives during

tenure and promotion review, and funding equity-focused fac­

ulty chairs that offer salary support for BAJEDI work. While

the demographic composition of career stages offers interest­

ing trends, it is important to note that these results represent a

limited sample and cannot be compared to the overall OSM24

attendee demographics, as information connecting conference

attendee gender to career stage is not available.

Survey results show that many individuals, particularly those

in minoritized communities and heterosexual white women,

continue to experience marginalization within ocean sci­

ences (Figure 2b,c). On average, minoritized individuals and

heterosexual white women personally experienced bias, dis­

crimination, or bullying in the past two years at rates that

were statistically higher than those experienced by hetero­

sexual white men (48%, 58%, and 0%, respectively, Figure 2c;

ANOVA F(2, 90) = 3.09, p ≪ 0.05). Similar results were seen when

participants were asked if they had personally witnessed bias, dis­

crimination, or bullying: minoritized individuals and heterosex­

ual white women were significantly more likely to respond in the

affirmative (69% and 84%, respectively), compared to only 15%

of heterosexual white men (Figure 2b; ANOVA F(2, 90) = 3.09,

p ≪ 0.05). Minoritized individuals and women reported statisti­

cally similar levels of both experiencing and witnessing bias and

discrimination (Welch’s t-test, p > 0.05 in both cases). In gen­

eral, prior studies have shown that minoritized individuals and

FIGURE 2. Career stage distri­

bution (a) and responses from

questions 1 (b) and 2 (c) of sur­

vey respondents broken down

into broad demographic cat­

egories. Minoritized individ­

uals and heterosexual, white

women both personally wit­

nessed (b) and personally

experienced (c) similar levels

of bias discrimination, or bully­

ing, and these rates were sta­

tistically greater than those

witnessed or experienced by

heterosexual white men.

June 2025 | Oceanography

61

women generally underreport incidents of harassment (Graaff,

2021). It is important to note that while minoritized individuals

and heterosexual white women both reported high rates of both

personally experiencing and witnessing discrimination, 85% of

heterosexual white men reported that they had not witnessed

any bias, discrimination, or bullying over the same period. These

responses highlight a known phenomenon, whereby men are less

likely than women to recognize instances of bias and discrimi­

nation (Davis and Robinson, 1991; Major et al., 2002; Drury and

Kaiser, 2014; Liao et al., 2016) unless they have personally been

the target of such behavior (Cech, 2024). Results from the survey

indicate a continuing need for strategies to address systemic bias,

discrimination, and bullying in ocean sciences. To that end, we

now turn to the TOS JEDI town hall discussion and the resultant

conversations on successful models for increasing equity, strat­

egies to improve accessibility, and methods for creating a more

just and fair culture within the ocean sciences community.

Successful Models

During the open discussion period of

the town hall, one group of participants

focused on the question, “What are some

successful models of expanding partici­

pation of minoritized and/or historically

marginalized individuals in ocean and

coastal sciences?” Based on this discussion,

we have compiled a list of known affin­

ity groups supporting underrepresented

researchers in ocean sciences (Table 1). This

list has been expanded to include groups

not discussed within the town hall; how­

ever, this summary should not be consid­

ered comprehensive. Finding community

and building connections play crucial roles

in increasing participation and retention

(Canfield et al., 2023; Hansen et al., 2024).

This pursuit also improves the quality of

science produced, as more diverse teams

have been shown to produce higher-impact

science than demographically homoge­

neous teams (Freeman and Huang, 2014).

Here, we include a few examples of groups

at the forefront of attracting, supporting,

and retaining individuals in ocean sciences

to improve BAJEDI.

Organizations focused primarily on

attracting minoritized individuals to ocean

sciences include the Online Conversations

for Equity, Action, and Networking

(OCEAN) project, which amplifies voices

from marginalized groups within ocean

sciences (Johanif et al., 2023), and Black in

Marine Science (BIMS), which uplifts Black voices in marine sci­

ences. These groups offer critical programs to attract and engage

future scientists at the undergraduate level, or earlier. BIMS

YouTube series airs weekly, engaging both adults and children.

Some groups focus more on supporting minoritized students

during their academic careers by offering internships, profes­

sional development, and mentorship opportunities. Such pro­

grams include the Community College Comprehensive Research

Experience (CC-CREW) at the Woods Hole Oceanographic

Institution, Minorities in Shark Science (MISS), National

Center for Atmospheric Research’s Significant Opportunities in

Atmospheric Research and Science (SOARS), and Sea Grant’s

Community Engaged Internship (CEI). MISS ran its pilot pro­

gram “Diversifying Ocean Sciences Project” in 2023 with 100%

of participants rating it as a valuable experience and noting that

networking and feeling like they were part of a community were

the most important experiences. Directed at undergraduates,

Sea Grant’s CEI engages undergraduates and community college

students in place-based research with an emphasis on local and

Indigenous knowledge.

TABLE 1. Known affinity groups supporting underrepresented researchers in the ocean sci­

ences. This list was compiled from the town hall discussion and expanded to include other

groups not discussed within the town hall; however, this summary of groups should not be

considered comprehensive. A more extensive list of affinity groups is available in Table S1 in

the online supplementary materials.

AFFINITY GROUP

Alaska Native Science & Engineering Program (ANSEP)

Asian Americans and Pacific Islanders in Geosciences (AAPIIG)

Black in Geoscience

Black in Marine Science (BIMS)

Black Women in Ecology, Evolution, and Marine Sciences (BWEEMS)

Community College Comprehensive Research Experience at WHOI (CC-CREW)

Community Engaged Internship (CEI)

Earth Science Women’s Network (ESWN)

GeoLatinas

International Association for Geoscience Diversity (IAGD)

Mentoring Physical Oceanography Women+ to Increase Retention (MPOWIR)

Minorities in Shark Science (MISS)

Minorities Striving and Pursuing Higher Degrees of Success in Earth System Science (MS PhDs)

National Association of Black Geoscientists (NABGG)

Online Conservations for Equity, Action, and Networking (OCEAN)

Philippine-American Academy of Science & Engineering (PAASE)

Significant Opportunities in Atmospheric Research and Science (SOARS)

Society for American Indian Science and Engineering Society (AISES)

Society for Advancement of Chicanos/Hispanics and Native Americans in Science (SACNAS)

Society of Women in Marine Science (SWMS)

UN Decade of Ocean Science for Sustainable Development

Unlearning Racism in GEosciences (URGE)

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62

Finally, some programs focus on long-term community

building to improve the retention of minoritized individuals.

These programs include Black Women in Ecology, Evolution,

and Marine Sciences (BWEEMS), Society for Advancement

of Chicanos/Hispanics and Native Americans in Science

(SACNAS), Mentoring Physical Oceanography Women+ to

Increase Retention (MPOWIR), Earth Science Women’s Network

(ESWN), Society of Women in Marine Science (SWMS), and

Unlearning Racism in Geoscience (URGE). BWEEMS and

ESWN work to connect women, elevating their voices and sup­

porting authentic connections with one another. ESWN, estab­

lished in 2002, has an expansive network, connecting over

8,000 women. SACNAS, operating since 1973, supports scien­

tists through multiple opportunities that include the National

Diversity in STEM Conference (NDiSTEM), the “largest multi­

disciplinary and multicultural STEM diversity conference in the

country” (Fenster and Verdier, 2023). MPOWIR focuses on the

retention of women and minoritized genders, referred to collec­

tively as women+ in the MPOWIR lexicon, in physical oceanog­

raphy through organized mentorship and professional develop­

ment opportunities beyond an individual’s home institution. As

of 2018, MPOWIR reported that an impressive 80% of partici­

pants who earned their PhDs between 2005 and 2012 remained

in the field (Mouw et al., 2018). SWMS, founded in 2014 and

with over 460 members as of 2023, utilizes symposia, workshops,

and webinars to engage women in a shared sense of community

and belonging. This organization’s work has “demonstrated the

effectiveness and importance of adaptive affinity-focused groups

and events in ocean sciences” through analysis of their symposia

(Canfield et al., 2023). The URGE program has been aiding the

community in developing meaningful institutional programs

since 2020, with specific directives toward educating non-​

minoritized individuals on the effects of racism on the retention

of people of color in the geosciences, instituting collaborative

institution policy reform, and sharing resources for consider­

ation when designing more equitable institutional policies.

At an international level, frameworks like the Ocean’s Benefits

to People (OBP) and the UN Decade of Ocean Science for

Sustainable Development (2021–2030) continue to support sci­

entists in their career paths. OBP prioritizes the integration of

local communities into ocean governance and policymaking

(Belgrano and Villasante, 2020), while the UN Decade of Ocean

Science for Sustainable Development (2021–2030) presents a

pivotal framework for BAJEDI efforts and initiatives in its goal

to include diverse perspectives in ocean sciences (Polejack, 2021;

Harden-Davies et al., 2022; Sun et al., 2022).

In discussing support structures offered by affinity groups,

town hall participants also touched on the disconnected natures

of many programs. Group members noted that many BAJEDI

programs operate independently, without unifying, inter-​

institutional structures. Group members felt that unifying struc­

tures, particularly for programs focused on undergraduate

education and retention, would provide greater community sup­

port and professional networking. The idea of a unifying, inter-​

institutional structure was underscored by another core topic

that focused on the necessity of strong cohort building within

equity programs. Here, cohort refers to an intentionally orga­

nized group for a minoritized and/or marginalized community

that progresses through education stages together (e.g., a cohort

of graduate students of color who begin a graduate program the

same year). Individuals who participate in the cohort may have

shared life experiences related to their minoritized identity and

may face similar experiences of inequity in ocean sciences. To

build strong cohorts, the group’s discussion identified three guid­

ing tenets: (1) offer individuals facilitated networking opportuni­

ties, (2) remove financial barriers to participation, and (3) engage

in robust post-program follow-up and continued engagement

with cohort members. Within STEM, cohorts focused on reten­

tion of minoritized individuals are shown to be successful when

multi-avenue support structures are available (Hansen et  al.,

2024), as seen in the high retention rate (80%) of the cohort-​

focused MPOWIR program. Within MPOWIR, early-​career

participants are grouped with similar career-stage peers at dif­

ferent institutions than their own, and two senior leaders con­

vene monthly group mentoring over the course of two to three

years. This continuity in mentorship through career transitions

positively supports retention of women in the field (Mouw et al.,

2018). The Possee Foundation is another excellent example of a

unifying, inter-institutional structure that specifically focuses on

cohort-based retention strategies. The Posse Foundation works

with dozens of undergraduate institutions to improve the reten­

tion of students of color in STEM fields, including post-program

community engagement, and boasts an impressive 90% gradu­

ation rate for students in its programs (The Posse Foundation,

2024). Initiatives focused on expanding the participation of

minoritized groups continue to grow, with numerous programs

emerging to address inequities in ocean sciences since 2020.

Mirroring the increase in programs directed toward improving

participation in ocean sciences, 60% of publications related to

ocean equity and justice have been published since 2020 (de Vos

et  al., 2023). While this recent focus on equity initiatives is

encouraging, it is important to acknowledge that the actual effi­

cacy of this groundswell can be difficult to measure, as long-term

holistic demographic information is rarely publicly available.

Accessibility

Scientific institutions continue to implement initiatives to

improve BAJEDI within their communities. These include, but

are not limited to, more equitable hiring criteria and recruitment

practices, implementing codes of conduct, restructuring tenure

review to value equity work, and creating safe spaces for margin­

alized identities, such as LBGTQIA+ spaces. Professional soci­

eties play roles in these actions by providing safe spaces within

chapters, highlighting the work done by affiliated groups, and

June 2025 | Oceanography

63

providing equity models for individuals and institutions to

implement. While these initiatives can help make ocean careers

more accessible, and professional societies have done work to

make these spaces and policies more readily available, accessi­

bility remains a challenge. Responses to the OSM22 survey sug­

gested that gatekeeping was the most significant challenge to

diversifying the ocean sciences (Meyer-Gutbrod et  al., 2023).

Gatekeeping refers to the intentional reduction of access to pro­

fessionally beneficial activities, particularly by limiting mar­

ginalized and minoritized groups. Early engagement, free from

gatekeeping, is critical to increasing access to ocean sciences.

Early engagement should be supported by equitable access to

meaningful professional development experiences through paid

internships (Kreuser et al., 2023) and more flexible introductory

research opportunities.

The survey and group discussions also touched on factors

outside an institution that impact the possibility of successful

BAJEDI programs. In particular, groups discussed how regional

and national political agendas may hamper efforts to improve

equity. Nearly one-third (27%) of the OSM24 survey respon­

dents live in a region with anti-BAJEDI legislation, 43% live in

regions currently unaffected by such legislation, and 30% were

unsure of the local legislative atmosphere. Much of the discus­

sion within this breakout group focused on strategies to make

ocean careers safe for minoritized individuals in light of these

political and legislative landscapes. Participants suggested hav­

ing open conversations with visiting scholars before their arrival

and with applicants during the application process. These may

be facilitated by a brief survey to prospective professional visi­

tors to an institution, which could ask guided questions on what

types of information the visitor would be interested in being

briefed on (example topics include results from previous insti­

tution climate surveys on the experience of minoritized groups

at the institution, and LGBTQ+ topics, including the availabil­

ity of health care). Upfront discussions would allow individuals

to pick environments where they can expect to live safely, even if

that may mean turning down opportunities. Institutions should

also actively advertise resources available to assist individuals,

including appropriate safety policies, reporting measures, and

health resources. This information should be readily available

to current and prospective employees and students. Required

training for principal investigators on the socio-political con­

ditions in geographic regions new to their lab (e.g., visited for

conferences, fieldwork) will aid in preparing for unfamiliar leg­

islative landscapes. Principal investigators are responsible for

educating all trainees on safety in these regions in order to pro­

tect their direct reports and affiliates.

These issues are broader than ocean science and STEM

careers, with significant backlash against DEI progress, increas­

ing legislative attacks aimed at transgender and gender-​

expansive communities, and the elimination of federal DEI

resources by the US government in January 2025, subsequent to

the writing of this article. Ensuring safe working environments

for all individuals, particularly in our current socio-political

climate, was of top concern among our town hall participants.

In addition to addressing barriers to access, the ocean sciences

community must take a leading role in fostering safe and equi­

table access to places and spaces unique to the field, including

shipboard, coastal, and remote environments (for an example,

see McMonigal et al., 2023). Discrimination is still happening

at the institutional level and should be openly acknowledged.

Institutions can and should put resources in place to protect

their workers and students. Furthermore, institutions and col­

leagues can advocate for safe and inclusive legislation as it per­

tains to their working environments.

Just and Fair Culture

As we strive for an increasingly inclusive ocean sciences commu­

nity, the importance of retention cannot be overstated. Standing

in the way of retention is a disconnect between the lived expe­

rience of minoritized individuals and recognition of this lived

experience by individuals who are not marginalized or minori­

tized. Participants in this town hall reflect this divide. As shown

in the OSM24 survey results and previous studies, groups who do

not experience systemic prejudicial bias, in this case, heterosex­

ual white men, appear to be less aware of the lived experiences of

gender and racial minorities (Figure 2b,c; Davis and Robinson,

1991; Major et  al., 2002; Drury and Kaiser, 2014; Liao et  al.,

2016). The survey data demonstrate that minoritized individu­

als and white heterosexual women experience greater marginal­

ization through bias, discrimination, and bullying (Figure 2c).

Increasing awareness of the lived experiences of those on the

receiving end of such behavior may strengthen understanding

in the community, particularly for those who do not personally

experience significant marginalization themselves, and increase

a sense of belonging for marginalized scientists.

To begin addressing this issue, town hall participants sug­

gested policies at the institutional/organizational, government

agency, and professional society levels. Participants discussed

how recent shifts in academic culture have resulted in apprecia­

ble advances in structural equity at the agency and institutional

levels. Institutional policymakers have the power to propel cul­

ture change by examining existing policies and evaluating those

policies from a BAJEDI perspective. Discussion group members

reflected on the need to uplift the voices of minoritized groups

during policy evaluation and reform. Scientists directly impacted

by such policies should feel ownership in improving them. To

this end, it is essential to center the voices of marginalized groups

in reforming inequitable policies, recognize equity work in per­

formance reviews, and ensure measures for accountability.

Promoting BAJEDI in ocean sciences will require a change

in resource allocation, hiring, promotion, tenure evaluation,

and recognition systems. Outdated academic productivity met­

rics center almost exclusively on funding acquisition, paper

Oceanography | Vol. 38, No. 2

64

production, and impact factors, with little or no regard for his­

torical intersectional layers of oppression that unequally impact

marginalized groups. For example, much of the work focused on

BAJEDI topics is executed by the very minoritized and margin­

alized individuals most affected by systemic inequity (Kamceva

et al., 2022). There is little recognition for these efforts, despite

the overall benefit to the community through the creation of

more diverse teams, which are known to produce better science

(Freeman and Huang, 2014). The actions and initiatives that

bring people together, build community, and ultimately advance

science are overlooked and undervalued in promotion and ten­

ure processes (Specht and Crowston, 2022). Broadening met­

rics to include service to affinity groups and incentivizing men­

toring options beyond traditional advisor/advisee relationships

would more accurately celebrate the various types of contribu­

tions that are meaningful to the success of the scientific com­

munity. There was general consensus among town hall attendees

that focusing on building community, increasing awareness, and

supporting cultural change with openness and curiosity would

allow for more inclusive, equitable policies. Reviewing the pres­

ent system and broadening achievements beyond scientific work

would foster a more just, equitable, and resultantly inclusive

academic community.

CONCLUSIONS

Survey results and input from participants at the OSM24 town

hall present a picture of an ocean science community actively

attempting to address persistent inequity within its ranks. A great

deal of work is still needed to achieve equity and foster a sense of

belonging and inclusivity for historically minoritized and mar­

ginalized groups. Survey responses from members of the ocean

sciences community point to increasing inclusivity but continued

challenges, including inequitable representation of minoritized

groups, lack of inclusive research opportunities, and antiquated

academic productivity metrics. The rise of more professional

societies, affinity groups, and other organizations that support

diverse people participating in ocean sciences was identified as

a major strength by town hall participants. Larger professional

societies can support smaller affinity groups by raising visibility,

encouraging inter-group professional networking, and highlight­

ing their achievements in national publications. Table 2 provides

an overview of the major action item recommendations.

The current lack of publicly available demographic informa­

tion continues to hamper the transparent assessment of BAJEDI

initiatives. Without these data, it is impossible to assess changes

in the demographic composition of the ocean sciences com­

munity as a result of BAJEDI-focused programs. Instituting an

opt-in model to collect such data from professional societies

and conference attendees would be a useful step toward closing

this data gap. Collecting and analyzing demographic data would

allow better understanding of the efficacy of current BAJEDI

initiatives and implementation of data-driven improvements.

Greater collaboration with social scientists and higher edu­

cation researchers is needed to accomplish this work in a just,

fair, and robust manner. In addition to thoughtful data collec­

tion and analysis, organizations and professional societies need

to critically and carefully consider how to store and use demo­

graphic data, as it may have personally identifiable information.

Furthermore, organizations and societies should collaborate to

ensure use of consistent categories and data collection methods

across surveys, as is common in large-scale data inter-​calibration

efforts within the ocean sciences. As responsible stewardship of

data requires financial resources, we encourage professional and

scientific societies to seek funding for this purpose.

TABLE 2. Action items to promote equity.

RECOMMENDATION

INTENDED IMPACT

EVIDENCE-BASED

SUPPORT

Collect and maintain an open-access demographic

database collected from surveys with consistent and holistic

demographic categories.

To allow for long-term assessment of the efficacy

of BAJEDI initiatives.

Hughes et al. (2022)

Support and promote affinity groups and smaller

professional societies and their activities.

To promote smaller, grassroots initiatives.

Canfield et al. (2023)

Fenster and Verdier (2023)

Mouw et al. (2018)

Collaborate with research centers and academic institutions

to provide flexible, paid research opportunities.

To lower barriers to entry for research activities.

Kreuser et al. (2023)

Increase the value of BAJEDI actions, which are often

carried out by minoritized and marginalized scientists, in

hiring and promotion decisions.

To increase participation in BAJEDI activities

and equitable valuation of professional BAJEDI

activities.

Specht and Crowston (2022)

Increase communication and collaboration between groups

working on related BAJEDI initiatives.

To increase professional networking and support

opportunities by leveraging the combined power

of currently disparate BAJEDI programs.

Jones and Were (2008)

Singh et al. (2012)

Fund first-year graduate fellowships accessible specifically

to minoritized groups, as is currently common for first-year

fellowships for women.

To increase matriculation of historically under­

represented minoritized groups in the ocean

sciences.

Piper and Krehbiel (2015)

Stolle-McAllister et al. (2011)

June 2025 | Oceanography

65

SUPPLEMENTARY MATERIALS

The supplementary materials are available online at https://doi.org/10.5670/

oceanog.2025.306.

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AUTHORS

Julien T. Middleton (jtmiddleton@ucsb.edu), Marine Science Institute, University

of California, Santa Barbara, CA, USA. Sarah Clem, University of Rhode Island,

Narragansett, RI, USA. Katherine L. Gallagher, School of Marine and Atmospheric

Sciences, Stony Brook University, Stony Brook, NY, USA. Erin Meyer-Gutbrod and

Amadi Afua Sefah-Twerefour, University of South Carolina, Columbia, SC, USA.

Margrethe H. Serres, Woods Hole Oceanographic Institution, Woods Hole, MA,

USA. Mona Behl, University of Georgia, Athens, GA, USA. James Pierson, Center

for Environmental Science, University of Maryland, Cambridge, MD, USA.

ARTICLE CITATION

Middleton, J.T., S. Clem, K.L. Gallagher, E. Meyer-Gutbrod, A.A. Sefah-Twerefour,

M.H. Serres, M. Behl, and J. Pierson. 2025. Community recommendations on

belonging, accessibility, justice, equity, diversity, and inclusion initiatives in ocean

sciences: A town hall discussion. Oceanography 38(2):58–65, https://doi.org/​

10.5670/oceanog.2025.306.

COPYRIGHT & USAGE

This is an open access article made available under the terms of the Creative

Commons Attribution 4.0 International License (https://creativecommons.org/

licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and repro­

duction in any medium or format as long as users cite the materials appropriately,

provide a link to the Creative Commons license, and indicate the changes that

were made to the original content.

Oceanography | Vol. 38, No. 2

66

DIY OCEANOGRAPHY

THE PIXIE

A LOW-COST, OPEN-SOURCE, MULTICHANNEL IN SITU

FLUOROMETER APPLIED TO DYE-TRACING IN HALIFAX HARBOR

By Kyle Park, Dariia Atamanchuk, Aaron MacNeill, and Vincent Sieben

INTRODUCTION

Submersible, or in situ, fluorometers are devices used in fresh­

water and marine environments to measure the presence of

compounds (fluorophores) that fluoresce when exposed to spe­

cific wavelengths of light. These measurements can be used,

for example, as indicators of water quality, contamination, and

flow dynamics. The earliest submersible fluorometers (Wheaton

et al., 1979) were designed with a single channel (i.e., measur­

ing fluorescence at a specific wavelength while rejecting the

rest of the spectrum). However, the presence of multiple fluo­

rescent species in natural waters makes it sometimes challeng­

ing to attribute the measured signal to a single compound with

certainty due to spectral overlap, so multichannel fluorometers

have been employed more recently.

Climate change and its associated impacts are increasing

the demand for high-resolution monitoring of the environ­

ment using optical sensors that enable fast detection and are

small enough to be integrated into mobile platforms. For exam­

ple, harmful algal blooms (HABs) can cause billions of dol­

lars in direct damages to fisheries (Davidson et al., 2020) and

fishery-​dependent communities (Weir et al., 2022), and reduce

the socioeconomic value of recreational areas (Mardones et al.,

2020). Preventative and mitigative actions can be taken if

warning signs, such as the concentrations of the fluorophores

chlorophyll a (Chl-a) and phycocyanin (PC) (Shen et al., 2012),

are monitored and detected early (Davidson et  al., 2020).

In another example, the assessment of marine carbon diox­

ide removal strategies, such as point-​source oceanic alkalinity

enhancement, requires a careful understanding of the near-field

dynamics that are studied using dye tracer experiments (Fennel

et  al., 2023). These experiments use fluorescent rhodamine

water tracer (RWT) dye to make spatio-​temporal measure­

ments of dye plume dispersion. In another example, petroleum-​

derived contaminants such as crude oil can be detected using

ultraviolet fluorometry. Overall, the scope and scale of human

activity put enormous pressure on the global ocean and water­

ways, thus warranting the development and improvement of

autonomous sensors, including fluorometers, for improved

monitoring and response.

Access to this technology as well as to the education required

to take advantage of it, both currently dominated by high-​

income countries, is a challenge recognized by the United

Nations Decade of Ocean Science for Sustainable Development

(2021–2030) (Harden-Davies et  al., 2022). The current price

of relevant industrial, single channel, in situ fluorometers is

$3,400–$7,800 USD (Park et al., 2023). Industrial multichannel

systems such the three-channel RBRtridente (RBR Ltd., Ottawa,

Canada), Turner C3 (Turner Designs, San Jose, CA), or ECO

Puck (Sea-bird Scientific, Bellevue, WA) have price and perfor­

mance characteristics comparable to the single channel devices

on a per-channel basis. To improve access and the use of sensor

technology, the documentation on some oceanographic devices,

their construction, use, and handling have been released to

the public as open source (Butler and Pagniello, 2021; see also

https://tos.org/diy-oceanography for additional open-source

instrument projects published in Oceanography).

ABSTRACT. Fluorometers are ubiquitous tools in the fields of oceanography, limnology, and water quality assessment. Fluorescent

species in our waters range from in vivo chlorophyll, contaminants like crude oil, or intentionally added agents like rhodamine.

Submersible in situ fluorometers can collect real-time data at scales that cannot be matched by discrete bottle samples with lab/​

shore-side analysis. However, accessibility of sensors remains a problem recognized by the United Nations Sustainable Development

Goals. Here, we introduce the PIXIE, an open-source, multichannel, in situ fluorometer that performs high-quality fluorometry

at a low cost. The PIXIE is assembled by simple means from almost entirely off-the-shelf components. The few necessary custom

parts are either easily outsourced or printed by consumer-grade 3D printers. The PIXIE draws an average of 225 mW during mea­

surement and has been tested to depths of 45 m. It has been calibrated to demonstrate a limit of detection 0.01 ppb rhodamine WT

(a fluorescent dye) in a range up to 60 ppb, and a limit of detection of 0.02 ppb chlorophyll a. The PIXIE has been deployed as part of

a dye-tracer experiment in Halifax Harbor, Canada, demonstrating its performance in a quasi-simultaneous profiling of rhodamine

WT dye and chlorophyll a.

June 2025 | Oceanography

67

Open-source/DIY fluorometers exist in the ocean sciences

space, with Chl-a fluorometers and “fluorometry-like” turbid­

ity (Matos et al., 2020) and backscattering sensors (Downing,

2006) being popular. Costs are low in most instances, though

two trends are noticeable. Either fluorometers tend to exhibit

detection limits of 0.1 μg L–1 (or 0.1 ppb) or higher (Leeuw

et al., 2013; Attivissimo et al., 2015; Park et al., 2023), which is

at least one order of magnitude worse than industrial sensors

(Park et al., 2023), or higher performing devices are configured

as benchtop units (Truter, 2015) and have not made the sacri­

fices necessary to package the technology into a form capable

of in situ deployment. The task of maintaining optical and elec­

trical performance in a small, water-tight, pressure-safe hous­

ing is not trivial, and making concessions on size/mass rules out

some of the most attractive use-cases of low-cost in situ fluo­

rometers (Dever et al., 2020; Park et al., 2023). Thus, there is a

gap in extant sensors between the advantages provided by open-

source in situ sensors and the performance provided by indus­

trial in situ fluorometers.

With this gap in mind, we introduce the PIXIE, a low-cost,

open-source, four-channel in situ fluorometer. In lab testing,

the PIXIE performs fluorometry with precision and accuracy

comparable to the sensors available on the market. The default-​

configuration PIXIE can be assembled for $1,392.75 USD with

one equipped channel. Each addition channel costs $525.25 USD,

for an average of $742.13 USD per channel when the instrument

is fully equipped.

For our work, a PIXIE unit was calibrated to demonstrate a

limit of detection (Arar and Collins, 1997; Sieben et al., 2010)

of 0.01 ppb RWT over a range 0 to ~60 ppb. The same unit was

calibrated to demonstrate a limit of detection of 0.02 ppb Chl-a

over a range of 0 to ~80 ppb. Deployed as part of a dye tracer

experiment in Halifax Harbor, Canada, (see Figure 1) to study

the near-field dispersion of RWT added to the cooling outfall of

the Tufts Cove Power Generation Station, the PIXIE was config­

ured to capture both RWT and Chl-a profiles, demonstrating its

multichannel functionality. The in situ data were checked against

discrete water samples collected in conjunction with the profiling

to assure quality, demonstrating how this low-cost, open-source

technology could assist in solving complex oceanographic tasks.

MATERIALS AND METHODS

Open-Source Fluorometer

The materials needed to assemble a PIXIE are available on

GitHub (https://github.com/KylePark0/PIXIE/tree/main), and

fall into one of three categories: documentation, firmware, or

hardware. The documentation includes a comprehensive user

guide that details the design, assembly, calibration, and opera­

tion of the device. Bills of materials (BOMs) are provided for the

mechanical and optical hardware, including vendors, and the

electrical BOM comes pre-packaged to fabricate with PCBWay

(PCBWay, Hangzhou, China). The listed optics include the com­

ponents needed to assemble any of five presets: PC, phycoeri­

thrin (PE), RWT, Chl-a, and crude oil. CAD models for every

component, including machined and 3D-printed parts, are

included. A rendering of the PIXIE with some dimensions (see

Figure 2) is provided, in both normal and exploded views.

The PIXIE can be powered using a range of 5–20 V. It com­

municates with an external terminal or datalogger via RS-232,

while drawing an average of 45 mA during active measurement

(225 mW). Using a dedicated 12 V lithium-ion cell with a nom­

inal capacity of two ampere-hours, the PIXIE can be expected to

measure for 40 hours in 4°C waters. Its off-the-shelf components

are rated for depths of at least 500 m. The housing is composed

of anodized aluminum and borosilicate glass, allowing it to with­

stand a range of solvents used in laboratory calibration of fluoro­

meters. Acetone is used to prepare standards of Chl-a (Arar and

Collins, 1997), a nearly-neutral phosphate buffer solution (PBS)

FIGURE 1. Drone photograph

of the August 2023 Halifax

Harbor tracer release experi­

ment conducted from the div­

ing vessel Eastcom. Insets: The

PIXIE open-source fluorometer

is shown mounted to the side of

a Niskin bottle (top) and during

rhodamine water tracer (RWT)

calibration (bottom) in the lab.

Oceanography | Vol. 38, No. 2

68

is used for solutions of PC (Jaeschke et al., 2021) and PE (Ardiles

et al., 2020), and deionized water is used for RWT. The PIXIE is

compatible with the above solvents but cannot tolerate the sul­

furic acid that dissolves quinine sulfate, the stand-in for crude

oil calibration. Sulfuric acid is used almost exclusively in lit­

erature to prepare fluorescence standards of quinine sulfate

(Kristoffersen et al., 2018).

Sensor Design

Design notes for the PIXIE, available in the PIXIE Complete

User Guide document provided at the GitHub link, are described

briefly here for context. The PIXIE was designed with a focus

on user configurability, and customization if desired. Users can

simply acquire the hardware and assemble the default configura­

tion or use the PIXIE’s documentation if more detailed custom­

ization is needed.

The PIXIE performs fluorometry using standard optics

through an O-ring-sealed glass window. The user configures the

targeted fluorophore for each of the four channels by selecting

the appropriate optical filters and excitation LEDs. The PIXIE

described in this work was equipped with hardware to target

PC, RWT, Chl-a, and crude oil, though only the RWT and Chl-a

channels were used. The PIXIE cannot measure using more than

one channel at a time, but it can cycle between channels fast

enough to achieve quasi-simultaneous measurements.

To extract only the fluorescence excited by the device itself,

the PIXIE modulates the brightness of its excitation LEDs sinu­

soidally. While the change in brightness is imperceptible to the

eye, the resulting fluorescence will have a synchronous bright­

ness that can be distinguished from other sources of light. This

allows PIXIE measurements even in bright laboratory or sun­

lit outdoor conditions. The process of measuring the sinusoidal

fluorescence and converting it to a measure of fluorophore con­

centration, or lock-in amplification, is implemented digitally and

can therefore be adjusted by more technically inclined users. The

PIXIE detects the sinusoidal fluorescence using an AC-coupled

transimpedance amplifier with a software-​configurable gain of

400 MΩ, within a sample volume of 0.1 mL. More technical

details can be found on our GitHub page.

Calibration

The PIXIE’s RWT and Chl-a channels were calibrated in the

laboratory using a set of temperature-controlled standards.

Fluorescence is known to depend strongly on temperature

(Smart and Laidlaw, 1977), so the PIXIE was calibrated across

a range of temperatures and concentrations. The set of tempera­

tures and RWT concentrations were chosen to parallel previ­

ous work in this area (Park et al., 2023) for comparison’s sake.

The protocols used were adapted from a US Environmental

Protection Agency Method 445 on Chl-a fluorometer calibra­

tion (Arar and Collins, 1997). An effort was made to adapt the

protocol to keep the number of expensive lab instruments and

equipment to a minimum, though the protocol applied to Chl-a

required a fume hood. The PIXIE was suspended above a beaker

such that its sensing end was submerged without overflowing

or trapping air bubbles (see Figure 1, bottom inset). A complete

description of the calibration protocols is available in the PIXIE

Complete User Guide document on GitHub.

Field Deployment

A 10 L Niskin bottle (General Oceanics, Miami, FL, USA) was

prepared for use during an RWT tracer release experiment in

Halifax Harbor, as depicted in Figure 1. The bottle was equipped

with a proprietary datalogger that powered an array of exter­

nal sensors, including for temperature and depth. The PIXIE

was also mounted to the Niskin bottle, pointed downward, and

constantly streamed its fluorometry data to the logger via the

RS-232 protocol at a frequency of 16 Hz.

On August 10, 2023, a pre-set amount of RWT was released

from the Tufts Cove Power Generation Station to study the

dye plume. Multiple sensors and techniques were used, includ­

ing the PIXIE-integrated Niskin bottle and an ecoCTD (Dever

FIGURE 2. The PIXIE, in assem­

bled view (left) and in labeled

exploded view (right). For clar­

ity, only one channel is popu­

lated with optics. Cable, exci­

tation LEDs, and some O-rings

are omitted.

June 2025 | Oceanography

69

et al., 2020) equipped with a Cyclops-7F rhodamine fluorome­

ter (Turner Designs). Discrete water samples were later analyzed

in the laboratory using a benchtop fluorometer. The Niskin bot­

tle was lowered into the water column and triggered at depths

ranging from 0.5 m to 45 m. The sampling was conducted on a

release day, a pre-release day (1 day prior) and a post-release day

(1–3 days later). The PIXIE captured the vertical RWT/Chl-a con­

centration profiles to demonstrate its multichannel functionality,

while the Niskin bottle provided a ground-truth measurement

of the RWT concentration at the surface and above the seafloor.

Data collected by each method were used to semi-quantitatively

validate the performance of the PIXIE as an in situ fluorometer.

RESULTS AND DISCUSSION

Calibration

A total of 37 data points was collected during the calibration of

the PIXIE’s RWT channel. These consisted of six standard con­

centrations across six temperature setpoints. The 60 ppb mea­

surement at 5°C saturated the device. A replacement 6.9°C tem­

perature set point was also collected. A total of 37 data points

were collected during the calibration of the Chl-a channel. The

80 ppb measurements at 5°C and 8°C saturated the device. A

replacement 9.6°C temperature set point was also collected.

The raw fluorescence data for each data point were collected

at the PIXIE’s maximum sample rate of 16 samples per second.

In line with previous work (Park et al., 2023), the raw data were

downsampled through a moving average of 16 samples, for an

effective sample rate of 1 sample per second. Fifteen minutes

of raw data were collected for each data point. During the last

five minutes, 300 samples were collected, and the mean of these

300 samples was taken as the calibration data point. The prior

10 minutes of data were inspected to ensure an apparent equilib­

rium fluorescence had been reached.

The six standard concentrations for each fluorophore

were used to generate a best-fit line for each temperature (see

Figure 3). In the 60 ppb RWT case, a 5°C data point was first

extrapolated from the six unsaturated temperature set points

(6.9°C as well as the original five). In the 80 ppb Chl-a case,

5°C and 8°C were first extrapolated from the five unsaturated

temperature set points (9.6 °C as well as the original four). The

parameters of the resulting curves do not change significantly

between the inclusion or exclusion of the extrapolated points.

The coefficient of determination (R-squared) for each calibra­

tion curve exceeded 0.99 for RWT and 0.98 for Chl-a.

FIGURE 3. (a) Rhodamine water tracer (RWT) calibration curves, with a dashed line indicating saturation. The extrapolated point is encircled. Inset: Plot

with concentration-equivalent 10-sigma error bars. (b) RWT temperature compensation “slope of slopes” curve. (c) Chl-a calibration curves, with a

dashed line indicating saturation. Extrapolated points are encircled. Inset: Plot with concentration-equivalent 1-sigma error bars, illustrating sensitivity to

bubbles. (d) Chl-a temperature compensation “slope-of-slopes” curve.

Oceanography | Vol. 38, No. 2

70

To compensate measurements for the temperature of the

sample volume, the slopes of each fit line are plotted, and a best-

fit line is calculated. From the parameters of this fit, the all-cause

temperature exponent can be approximated. The PIXIE achieved

an approximate temperature exponent of –0.019°C–1 for RWT,

consistent with previous results (Park et al, 2023). For Chl-a, the

approximate temperature exponent obtained was –0.008°C–1,

which is consistent with equivalent temperature parameters for

Chl-a from the literature (Watras et al., 2017). The coefficient of

determination for these curves exceeded 0.99.

The standard deviation of each 0 ppb (blank) data point was

calculated. Applying the calibration curves to these blank stan­

dard deviations, the limit of detection was taken as three times

the worst-case standard deviation across blanks. The limits of

detection were found to be 0.01 ppb for RWT and 0.02 ppb for

Chl-a. The upper limit of the PIXIE’s RWT detection range was

found to be 58.9 ppb at 5°C, whereas it was 87.7 ppb at 20°C.

For Chl-a, the upper limit of the detection range was found to

be 78.8 ppb at 5°C, whereas it was 90.2 ppb at 20°C. Further

details about these results can be found in the PIXIE Complete

User Guide on at the GitHub link. Bubbles were observed during

two of the 40 ppb Chl-a calibration trials, resulting in anoma­

lously high standard deviations in those data sets as the bubble

periodically stirred through the sample volume. The inset plot of

Figure 3c illustrates 1-sigma error bars on the 40 ppb, 5°C data

point. This contrasts with the 10-sigma error bars on the 30 ppb,

5°C RWT data point illustrated in the inset plot of Figure 3a.

To directly compare the cross-sensitivity of the two chan­

nels to the opposite fluorophore, the PIXIE’s RWT channel mea­

sured a standard of Chl-a and vice-versa. A complete descrip­

tion of the comparison and its results (Figure S1) is available in

the online supplementary materials.

Field Deployment

Figure 4 depicts the first deployment of the PIXIE in August 2023

during the dye tracer release experiment. Three key stations’

worth of collected data are presented. Pre- and post-​release data

are provided to illustrate the PIXIE’s multichannel functional­

ity. The pre-release station was chosen based on depth and on

the availability of historical Chl-a profile data (Giesbrecht and

Scrutton, 2018), whereas the post-release stations were chosen

for their strong near-surface RWT concentrations as sampled by

the Niskin bottle, so that the measured profile and bottle samples

can be meaningfully compared. The PIXIE data were downsam­

pled to 1 sample per second to parallel the calibration results and

to align with the logger’s depth sensor data. With default gain

settings, the device saturation limits at 18°C are 82.3 ppb and

88.5 ppb for RWT and Chl-a, respectively. The channels’ data

are calibrated assuming a uniform temperature of 18°C. This

temperature is chosen to match the recorded in situ tempera­

ture of the surface Niskin bottle samples, rounded to the near­

est degree. The August surface bottle samples fell within a range

of 16° to 20°C, so the theoretical error in measurement is no

more than 5.1% (Smart and Laidlaw, 1976) for RWT and even

8/8/2023 16:14

b

8/10/2023 14:21

c

8/10/2023 16:54

d

FIGURE 4. (a) GPS paths of Eastcom on August 8, 2023 (violet path) and August 10 (indigo path). Stations 1, 2, and 3 indicate locations of the vertical

profiles in (b), (c), and (d), respectively. Inset: Station 2, magnified, indicates Tufts Cove Power Generation Station, the release site of the RWT. Red text in

the following indicates UTC time of profile start. (b) August 8 (afternoon) pre-release profiles show zero RWT response (top) and a Chl-a profile (bottom).

Solid curves indicate downcast, and dot-dashed curves indicate upcast. (c) August 10 (morning) post-release profiles stationed next to the RWT outflow;

RWT channel saturates near the surface, decently agrees with Niskin bottle sample (black asterisks). (d) August 10 (afternoon) post-release profiles were

made further along the anticipated path of the dye plume. Note modest underestimation of Niskin bottle RWT sample.

June 2025 | Oceanography

71

less for Chl-a. This would slightly overestimate the RWT con­

centrations in deeper/colder water, but no RWT was detected

from the bottom-​depth Niskin bottle samples.

The map provided in Figure 4a illustrates the GPS paths of the

diving vessel Eastcom used for the deployment. The labeled sites

indicate the profile locations: Stations 1, 2, and 3 in Figure 4b,

4c, and 4d, respectively. The bright colored curves indicate mea­

surements while downcasting, whereas the darker dot-dashed

curves indicate upcasting. The results from the Niskin bottle sam­

ples are indicated with black asterisks. The bottom-depth Niskin

bottle samples were found to have no detectable RWT across the

entire data set, in agreement with the PIXIE measurements.

The profiles in Figure 4b were captured on August 8, 2023,

two days prior to dye release. No dye was detected while some

Chl-a was detected at Station 1, the location of the DRDC

(Defence Research and Development Canada) Atlantic Acoustic

Calibration Barge. The vertical Chl-a profile measured by the

PIXIE shows qualitative agreement with historical observations

(Giesbrecht and Scrutton, 2018). The Chl-a concentration maxi­

mized by 10 m depth and returned to zero/background by 15 m

depth on downcast, though the significant difference in time of

day, season, and year confounds their quantitative comparison.

The upcast profile appears in sharp contrast to the presented

and historical downcast profiles. Because this station achieves

the greatest cast depth of 45 m among the dataset, this discrep­

ancy between downcast and upcast may indicate a pressure hys­

teresis effect (Shigemitsu et al., 2020) that is uncharacterized and

warrants future investigation.

The profiles in Figure 4c were captured on August 10, 2023,

during the RWT release at Station 2, directly in front of the

Tufts Cove Power Generating Station effluent where the RWT

was released. The RWT channel saturates immediately below

the surface (>82.3 ppb RWT), confined to an apparent stratum

between 1 m and 5 m depths. This indicates a subduction of the

RWT plume that can be confirmed visually in Figure 1, but the

exact mechanism of this stratification is beyond the scope of

this article. The surface-depth Niskin bottle sample recorded an

RWT concentration of 217.8 ppb, clearly in excess of the PIXIE’s

saturation limit. A second, near-surface bottle sample (3.7 m)

recorded a concentration of 10.7 ppb, in good agreement with

the PIXIE’s measurement of 14.5 ppb. The discrepancy between

bottle and PIXIE measurements at this depth could be attributed

to the difference in interrogated volume at this point. The profile

suggests that the bottle sample was taken at the edge of a steep

RWT gradient. The point sampling of the PIXIE’s measurement

is therefore more sensitive to depth than the ~1 m concentration

gradient over which the Niskin bottle averages.

The profiles in Figure 4d were captured on August10, 2023,

three hours later at Station 3, along the anticipated path of the

RWT plume. The RWT channel detected a weaker but cer­

tainly present signal (10 ppb) in the first 2 m and returned to

zero by 5 m depth. The surface Niskin bottle sample recorded

an RWT concentration of 15.7 ppb, in modest agreement with

the PIXIE’s measurement. The Chl-a channel shows a simi­

lar characteristic to that observed at the previous station, with

no apparent dependence on the presence/absence of the large

(>200 ppb) RWT plume.

To further validate the performance of the PIXIE, the

August 10, 2023, profile at Station 3 can be compared to the near­

est RWT transects captured by the ecoCTD, occurring just after

the Niskin bottle samples were collected. See the online supple­

mentary materials for a summary of the comparison of the two

sets of profiles along with a waterfall plot (see Figure S2).

CONCLUSIONS

The PIXIE is a low-cost, open-source, multichannel fluoro­

meter that demonstrates performance comparable to indus­

try standards. It can be assembled at a cost to the end user of

$741.38  USD per channel on average, and alternate configu­

rations can be even less expensive. While this cost should not

be compared to the internal cost-per-unit of industrial in situ

fluorometers and the end user must consider the value of the

support and quality assurance industrial devices enjoy, the

PIXIE nevertheless represents an open-source option with sim­

ilar performance and a low barrier to entry. The PIXIE’s limit of

detection is 0.01 ppb RWT and 0.02 ppb Chl-a, which is on par

with other in situ fluorometers. The PIXIE was successfully field

deployed and validated as a part of a dye-tracer experiment in

Halifax Harbor. The full availability of the PIXIE’s source files,

from hardware to firmware, allows the end user to customize

the PIXIE as much or as little as desired. The PIXIE makes a

transformative leap in accessibility that can meet the growing

demands for spatio-temporal data from our planet’s waterways,

without sacrificing measurement quality.

POSSIBLE FUTURE DEVELOPMENT

A road map of future work is proposed within the PIXIE

Complete User Guide available on the GitHub project page.

Hysteresis has been identified (Briggs et al., 2011; Cetinić et al.,

2012) as a common problem in fluorometers and similar in situ

devices, and the degrees along which the PIXIE exhibits it should

be studied explicitly. With some modifications to the front end,

the PIXIE could include turbidity and backscattering as poten­

tial channel types along with its current fluorometric channels.

Internal temperature sensing can be integrated through firm­

ware, and external (in situ) temperature sensing could be per­

formed in place of one of the fluorometric channels with only

minor hardware changes. More details toward each of these pro­

posed areas of future work can be found on GitHub.

SUPPLEMENTARY MATERIALS

The supplementary materials are available online at https://doi.org/10.5670/

oceanog.2025.309. To access the PIXIE fluorometer files on GitHub, go to:

https://github.com/KylePark0/PIXIE/tree/main.

Oceanography | Vol. 38, No. 2

72

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ACKNOWLEDGMENTS

We would like to thank Teo Milos, Mickey Jackson, Chidinma Onumadu, and

Rehan Khalid for their senior-year project contributions in the end-cap design.

We also would like to thank Iain Grundke, Edward Luy, and James Smith, from

Dartmouth Ocean Technologies Inc. for advice in the early stage of the proj­

ect. This work was funded in part by the Canada First Research Excellence Fund

(CFREF) through the Ocean Frontier Institute (OFI) and Transforming Climate

Action (TCA), the National Sciences and Engineering Research Council (NSERC)

of Canada, and the Canadian Foundation for Innovation John Evans Leadership

Fund. We would like to thank Ruth Musgrave, Ruby Yee, and Mathieu Dever for

their contribution of fluorometry data from their transect study to this work. We fur­

ther acknowledge the funding sources of their contribution; the transect study

was funded in part by NSERC, the OFI, and the Trottier Family Foundation. The

fieldwork in Halifax Harbor was supported in part by the Carbon to Sea Initiative,

a multi-funder effort incubated by Additional Ventures, and the Thistledown

Foundation. We would like to thank Claire Normandeau, Jessica Oberlander, and

Lindsay Anderson for their help in analyzing RWT samples in the laboratory. We

would like to acknowledge support from Douglas Wallace in providing scientific

guidance and access to the infrastructure and materials at the CERC.OCEAN labo­

ratory. The maps provided in Figure 4 and Figure S2 contain information licensed

under the Open Government Licence – Canada.

AUTHORS

Kyle Park (kyle.park@dal.ca), Department of Electrical and Computer Engineering,

Dalhousie University, Halifax, Canada. Dariia Atamanchuk, Department of

Oceanography, Dalhousie University, Halifax, Canada. Aaron MacNeil and

Vincent Sieben, Department of Electrical and Computer Engineering at Dalhousie

University, Halifax, Canada.

ARTICLE CITATION

Park, K., D. Atamanchuk, A. MacNeill, and V. Sieben. 2025. The PIXIE: A low-cost,

open-source, multichannel in situ fluorometer applied to dye-tracing in Halifax

Harbor. Oceanography 38(2):66–72, https://doi.org/10.5670/oceanog.2025.309.

COPYRIGHT & USAGE

This is an open access article made available under the terms of the Creative

Commons Attribution 4.0 International License (https://creativecommons.org/

licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and repro­

duction in any medium or format as long as users cite the materials appropriately,

provide a link to the Creative Commons license, and indicate the changes that

were made to the original content.

June 2025 | Oceanography

73

OCEAN EDUCATION

HANDS-ON POST-CALIBRATION

OF IN VIVO FLUORESCENCE USING

OPEN ACCESS DATA

A GUIDED JOURNEY FROM FLUORESCENCE TO PHYTOPLANKTON BIOMASS

By Pierre Marrec, Amanda Herbst, Stace E. Beaulieu, and Susanne Menden-Deuer

PURPOSE OF ACTIVITY

The goal of this activity is to help students become acquainted

with key procedures in oceanographic data acquisition, pro­

cessing, validation, and management. These skills are learned

through using sensor-based underway fluorescence and dis­

crete chlorophyll a (Chl-a) measurements. By encompassing a

wide range of skills necessary for oceanographic research—from

at-sea operations, to precise lab work, to data management—

this activity showcases the diverse learning opportunities that

oceanography offers for educating science and engineering stu­

dents. This activity highlights the critical, yet often overlooked,

steps required to process and validate high-resolution data from

autonomous sensors, such as those mounted on ocean observ­

ing platforms (e.g., research vessels, moorings, gliders), before

utilizing them to investigate relevant oceanographic processes. It

offers students the opportunity to develop proficiency in the var­

ious steps of managing open-access data from diverse sources,

while also introducing them to the principles of findable, acces­

sible, interoperable, and reusable (FAIR) data practices in sci­

entific research (Wilkinson et al., 2016). Additionally, it famil­

iarizes them with the requirements of the Open-Source Science

Initiative (OSSI) for open, transparent, accessible, inclusive,

and reproducible science. Emerging mandates that make fund­

ing availability contingent on open data managing and sharing

procedures make the skills delivered in this activity essential for

researchers and technicians (Kaiser and Brainard, 2023).

AUDIENCE

This manuscript is designed for instructors, serving as a guide

to the various steps involved in sharing this activity with stu­

dents. The intended audience for this project is undergraduates

enrolled in advanced environmental science courses. However,

the activity could be adapted for a less advanced student audi­

ence by focusing only on a subset of the activities (e.g., plot­

ting and interpreting the data). Moreover, the activity is thor­

oughly documented, and all necessary data are provided in

the format required for sequential steps so that instructors can

choose the appropriate starting points for their students. This lab

could also be modified to suit students in a statistics or data sci­

ence course. The project was developed with coauthor Amanda

Herbst as part of her SURFO (Summer Undergraduate Research

Fellowship in Oceanography) REU (Research Experience for

Undergraduates) at the University of Rhode Island Graduate

School of Oceanography (URI-GSO). All the fundamental steps

of this project can be completed using basic computer resources

(e.g.,  Open Office Calc, Microsoft Excel) and do not require

students to have programming skills. However, it also offers

the opportunity for students to enhance their proficiencies in

coding (e.g., using R, MATLAB, or Python) by automating and

streamlining data management steps. Additionally, this project

could serve as a self-study guide for advanced students who may

not yet be familiar with the procedures and importance of data

quality control and management.

APPROACH

The approach taken in this laboratory is to familiarize students

with the essential steps for accessing, validating, sharing, and

interpreting phytoplankton biomass inferred from the fluores­

cence signal acquired by sensors mounted on different types

of ocean observing platforms. The laboratory session includes

two main activities: (1) accessing both underway fluorescence

and discrete Chl-a measurements extracted from samples col­

lected during oceanographic cruises, and (2) post-calibrating

the fluorescence data with discrete Chl-a concentrations, inter­

preting the results, and publishing post-calibrated data. These

activities were conducted as part of the OCG561 – Biological

Oceanography Laboratory course at the University of Rhode

Island’s Graduate School of Oceanography, taught by coauthor

Menden-Deuer. The graduate students enrolled in this course

came from diverse backgrounds in oceanography, including

physical, chemical, geological, and biological disciplines. The

time allocations provided are approximate, and we encourage

Oceanography | Vol. 38, No. 2

74

instructors to adapt both the teaching approach and the struc­

ture of the activities to suit their specific student audiences. The

activity was performed during a single 3-hour laboratory class,

but based on our experience, dividing this activity into two sec­

tions and separate 1.5-hour classes, with at home preparation

taking no more than 1 hour (before each 1.5-hour classes) may

be better suited to student’s learning pace. Below, we present a

suggested structure for the activity, informed by our experience

teaching this lab and by student feedback.

BACKGROUND LECTURE (15 minutes)

Ideally, dedicate lecture time prior to the lab activities to intro­

duce the necessary concepts. Use the background sections pro­

vided as a guide for this session. To help provide context for stu­

dents and instructors without direct experience in oceanography,

we have included figures in the online supplementary materials

showing R/V Endeavor, the fluorometers installed on the under­

way system, and fieldwork from this project. This foundational

lecture is essential for preparing students for the lab.

SECTION 1 (1 hour of homework, 1.5 hours in class)

The data provided stem from six separate R/V Endeavor cruises.

A few days before the lab session, assign each student a unique

cruise dataset, ensuring one of each of the six cruises is covered

by at least one student. Provide each student with the lab instruc­

tions document, the corresponding .csv file, and the activity

template (all available in the online supplementary materials).

Groups of two to three students can also be considered.

As part of their homework (at most 1 hour), students should

review the instructions for both parts of the activity and work

through the first steps of Part 1 of Section 1. During the lab, the

instructor will guide students through the activity step-by-step,

ensuring everyone is able to complete the assigned tasks.

The instructor has access to all the final templates (in the

online supplementary materials) and formatted example figures

(created in MATLAB) to demonstrate expected results. Students

are encouraged to format their own figures, allowing for student

independence and creativity.

SECTION 2 (1 hour of homework, 1.5 hours in class)

Similar to Section 1, students should complete the steps of Part 1

independently before the lab session. The lab will begin by

reviewing their progress, focusing on the required linear regres­

sion. The instructor will compile students’ results and compare

them to the expected outcomes provided in the supplemen­

tary materials.

The second part of this section involves collaborative group

work, where students combine their results to address the pro­

posed questions. The activity concludes with a group discussion

on the significance of fluorescence data post-calibration, as well

as an exploration of data quality processes, FAIR principles, and

open-access data.

CLASSROOM DISCUSSIONS

Throughout both activities, we recommend incorporating

“council moments” where the instructor pauses the session to

address proposed questions and facilitate discussions. We pro­

vide sample questions and discussion topics.

BACKGROUND

We are in an era of big data, where high-resolution sensors mea­

sure and transmit information at unprecedented rates, partic­

ularly in the field of oceanography. Oceanographic data come

from a wide variety of sources, including sensors on ships,

observing platforms, and satellites. For these data to be use­

ful and accessible to diverse users, data need to be processed in

ways that adhere to strict scientific standards and made avail­

able as open access through data portals. Formalizing data han­

dling approaches has led to the development of FAIR principles

that make data findable, accessible, interoperable, and reusable

(Wilkinson et  al., 2016). We aim to demonstrate that critical

aspects of data validation and management require human-in-

the-loop intervention to ensure that data remain FAIR to the

scientific community.

Oceanic physical parameters (e.g.,  temperature, salinity,

depth) and biogeochemical parameters (e.g., dissolved oxygen,

bio-optical properties, nitrate, and carbonate system chemis­

try components) are routinely measured using sensors. These

sensors can be deployed on different platforms (research ves­

sels, mooring buoys, profiling floats, gliders) and can generate a

substantial volume of data. Interpreting environmental param­

eters recorded by autonomous sensors can be challenging, and

post-processing is required, even if they have been calibrated by

the manufacturer before deployment. Several factors can make

the manufacturer’s calibration insufficient for ensuring accu­

rate measurements, including sensor drift, mechanical issues,

and biofouling. While manufacturer-calibrated “raw” data offer

valuable insights into the relative changes in a given parame­

ter during deployment, our goal is to demonstrate the critical

importance of post-calibration to obtain accurate absolute val­

ues. These values are essential for making meaningful compar­

isons and supporting oceanographic research. Biogeochemical

parameters, such as dissolved oxygen or chlorophyll a (Chl-a)

fluorescence, provide good examples of the challenges asso­

ciated with post-calibration for research purposes, as they

require human-in-the-loop (HITL) calibration and valida­

tion (Palevsky et al., 2024). Using data obtained directly from

the sensor, with raw voltages/signals converted into parameter

concentrations using manufacturer-provided coefficients and

equations, can lead to erroneous absolute values and interpre­

tations. Therefore, developing and applying robust procedures

for both automated and HITL post-deployment data process­

ing is essential to produce science-ready data from bio-optical

and chemical sensors.

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75

PHYTOPLANKTON

Phytoplankton are photosynthetic single-celled microscopic

algae. They are primary producers that form the base of food

webs in aquatic ecosystems and play a key role in the global car­

bon cycle. Although phytoplankton only make up 0.06% of the

global primary producer biomass, they are responsible for nearly

half of Earth’s primary production (Stoer and Fennel, 2024).

Nearly all marine organisms rely directly or indirectly on the

organic matter or oxygen produced by phytoplankton through

photosynthesis. The key roles phytoplankton play in ocean eco­

systems and global biogeochemical cycles make phytoplankton

an essential component of oceanographic studies, from food

web processes to climate change.

HOW TO MEASURE PHYTOPLANKTON BIOMASS

USING A FLUOROMETER

Chl-a is commonly used as a proxy for phytoplankton biomass,

as all photosynthetically active phytoplankton use Chl-a as a pig­

ment to produce organic matter through photosynthesis. While

Chl-a concentration is relatively easy to quantify, Chl-a should

always be considered cautiously as a proxy for phytoplankton

biomass because of:

• Species Variability. Different phytoplankton species have

varying Chl-a concentrations per unit of biomass (often

expressed as C:Chl-a ratio, Geider, 1987; Smyth et al., 2023).

• Environmental Factors. Light availability, nutrient concentra­

tions, and other environmental conditions can influence and

rapidly change the amount of Chl-a phytoplankton cells con­

tain (Graff et al., 2015; Jakobsen and Markager, 2016).

• Phytoplankton Physiology. The growth and physiologi­

cal state of phytoplankton can affect Chl-a concentration

(Geider, 1987).

• Other Pigments. Not all phytoplankton rely solely on Chl-a.

Some species use different pigments for photosynthesis, and

pigments can interfere with fluorescence profiles.

Chl-a molecules fluoresce in the red wavelengths (695 nm)

due to higher absorption of light by Chl-a at the 460–470 nm

(blue) wavelength (Figure 1, Ocean Optics Web Book). Therefore,

Chl-a concentration can be quantified by measuring the emitted

fluorescence, with the intensity of the fluorescence signal being

proportional to the concentration of Chl-a pigment. The fluores­

cence intensity is first measured in volts (V) by the fluorometer

and then converted into Chl-a concentration using a set of coef­

ficients from calibrations performed by the manufacturer. Given

the sensitivity of fluorescence to ambient conditions, (e.g., light;

Graff et al., 2015), fluorescence may not be a reliable indicator of

actual Chl-a concentration.

Digression. A demonstration of these principles can be done

with a blue laser (e.g., pointers <$10 online) and a coastal water

FIGURE 1. (a) Illustration of the chlorophyll a (Chl-a) fluorescence principle and the

functioning of a fluorometer, representing the interactions between the pigment,

the light used for excitation, and the sensor used for detection of the emitted red

fluorescence. The (b) absorption and (c) fluorescence spectra of Chl-a in diethyl

ether (Dixon et al., 2005) are represented. Note the offset between absorption and

fluorescence peak wavelengths (EX: 420 nm and EM: 670 nm) in diethyl ether and

the wavelengths used by the fluorometer to detect Chl-a fluorescence in vivo in sea­

water (EX: 460–470 nm and EM: 695 nm).

Oceanography | Vol. 38, No. 2

76

(or lake, or any phytoplankton-rich water) sample, or even bet­

ter, with a phytoplankton culture in a test tube. With all human

eyes protected from exposure, point the blue laser at the tube in

the dark, and the Chl-a molecules present in the phytoplank­

ton will be seen to emit red light through fluorescence. Laser

light emission can be harmful to the eyes. Ensure you take pre­

cautions to avoid directing the laser beam toward anyone’s eyes.

Fluorometers used by oceanographers use exactly the same prin­

ciple, with a blue light exciting Chl-a present in natural assem­

blages of phytoplankton and recording the intensity of the red

light thus emitted.

LAB ACTIVITY

MATERIALS AND SKILLS NEEDED

The instructions for the lab activities are provided in the online

supplementary materials. The data required for the lab activi­

ties are also provided in the supplementary materials and are

accessible online through open-access databases and portals. To

facilitate the activities, open-access templates (OpenDocument

Spreadsheet, .ods) are included in the supplementary materials.

Additionally, .ods files containing the expected results for each

activity are provided to ensure students can complete all tasks,

even if they face challenges with specific steps. Instructors will

also find png-format figures illustrating each activity in the sup­

plementary materials.

Students need individual computers with internet access

and a spreadsheet application, such as OpenOffice Calc (open

access) or Microsoft Excel, to complete the activities. They

should be comfortable using spreadsheet software and familiar

with basic functions like copying and pasting, calculating aver­

ages and standard deviations, creating plots, and performing

linear regressions.

Instructors should be familiar with concepts in oceanogra­

phy (e.g.,  phytoplankton and fluorescence). While experience

with deploying oceanographic instruments, such as fluorom­

eters, and analyzing the resulting data can be helpful, it is not

required. However, proficiency in data handling and analysis

using spreadsheet software is highly recommended, as students

may encounter difficulties during the activities that require

additional support.

SECTION 1. ACCESSING AND EXPLORING

SENSOR-BASED FLUORESCENCE AND DISCRETE

CHL-A DATA (1.5 hours)

Accessing and working with observational data can be challeng­

ing due to material or geographical constraints that limit data

availability. Here, we aim to familiarize students with openly

accessible oceanographic data and to help them develop skills in

analyzing sensor-based fluorescence and discrete Chl-a data col­

lected as part of the Northeast US Shelf Long-Term Ecological

Research (NES-LTER) project. Students will work with authen­

tic data and learn quality control procedures, with the goals

of acquiring valuable skills and addressing critical questions

about data quality assurance and the management of obser­

vational datasets.

PART 1. SENSOR-BASED FLUORESCENCE CHL-a DATA

Goal. Access and work with authentic raw underway fluores­

cence data, followed by preliminary interpretation of these data.

Expected Outcomes. Develop familiarity with underway fluo­

rescence data, including the challenges of handling raw datasets

and navigating complex formats, such as date/time. Produce fig­

ures to interpret general patterns in the data and engage students

in critical discussions about the observed trends.

Narrative. Fluorometers that record Chl-a fluorescence are

widely used by the scientific community to estimate phyto­

plankton biomass in water bodies and to investigate the dynam­

ics of phytoplankton communities. Chl-a fluorescence data

can be found on many open access databases. Some examples

from US-based research programs are the University-National

Oceanographic Laboratory System (UNOLS) Rolling Deck to

Repository (R2R), the Environmental Data Initiative (EDI),

the Ocean Observatories Initiative (OOI), and the Biological &

Chemical Oceanography Data Management Office (BCO-DMO).

Here, we use data from six NES-LTER cruises (EN644, EN649,

EN655, EN657, EN661, and EN668) on R/V Endeavor. During

each cruise, a pump located near the ship’s bow collects water

from 5 m below the ocean’s surface through a system of tubing

throughout the ship—called an underway system. Such under­

way systems are present on most oceanographic research ves­

sels. The underway data are recorded along the cruise tracks and

include a suite of navigation (e.g.,  latitude, longitude, speed),

meteorological (e.g., wind speed and direction, light intensity),

and oceanographic (e.g.,  temperature, salinity, Chl-a fluores­

cence) data. On R/V Endeavor, some of the oceanographic data

collected are obtained from an underway water flow-through

system that includes temperature and salinity sensors, and two

fluorometers, a WETLabs ECO-FLRTD and a WETStar fluo­

rometer. Fluorescence is measured and recorded every second

along the ship track. The WETLabs ECO-FLRTD reads Chl-a

fluorescence by exciting at a wavelength of 460 nm, the WETStar

fluorometer excites at 470 nm, and both fluorometers read emis­

sions at 695 nm (Figure 1). The raw fluorescence is recorded in

volts (V) and then converted to Chl-a concentration expressed

in units of mg m–3 based on a manufacturer calibration using a

scale factor and blanks including pure water and dark counts.

Ship-provided raw underway data are publicly available through

the R2R data portal. Raw underway fluorescence data are

stored within the TSG Sea-Bird SBE-21 datasets, along with

other underway data such as temperature, conductivity, salin­

ity (Sosik, 2019, 2020a, 2020b, 2020c, 2021a, 2021b). These

raw data can be challenging to access because of their formats

June 2025 | Oceanography

77

(multiple, non-concatenated, .raw files), which are basically text

with separations (e.g., commas, but also tabs) between columns,

and without column headers. As part of the NES-LTER proj­

ect, curated 1-min temporal resolution data, including all nav­

igation and meteorological and oceanographic measurements,

can be accessed through the NES-LTER REST API in a comma-​

separated values (.csv) format that also includes all the column

headers. To facilitate access, we provide the underway data as

supplemental .csv files for several cruises as downloaded from

the NES-LTER REST API at the time this article was written.

The data show that the two fluorometers recorded slightly dif­

ferent values during each cruise but generally followed a sim­

ilar pattern (Figure 2 and in online supplementary materials).

During the winter 2021 (February) EN661 NES-LTER cruise,

the WetStar fluorometer was malfunctioning during the first two

days of the cruise, as indicated by the major differences observed

when comparing the two fluorometer values (Figure 2). A clean­

ing of the WetStar fluorometer was performed during the cruise

once the problem was identified, resulting in a better match

of the sensors afterward. We included these data here because

such technical problems occur frequently and highlight the

importance of cleaning oceanographic instruments before each

deployment, and also the importance of real-time monitoring of

the sensors’ displays during a cruise. The difference between the

two fluorometers appears to follow a diel cycle (Figure 2c and in

online supplementary materials), with a larger difference during

daylight hours, highlighting the fact that instruments measuring

the same parameters can produce different data and that those

deviations can be modified by external influences. This diel pat­

tern might be linked to non-photochemical quenching of Chl-a

molecules during the daytime (Marra, 1998; Xing et al., 2012),

when light intensity is high, with one of the instruments being

more sensitive than the other to this process.

PART 2. DISCRETE DATA FOR EXTRACTED CHL-a

Goal. Access and analyze authentic discrete Chl-a data, followed

by preliminary interpretation. Gain familiarity with the dataset

required for Section 2 of this lab activity.

Expected Outcomes. Build an understanding of discrete Chl-a

data, including how they are collected, the uncertainties associ­

ated with discrete sampling, and the quality control procedures

applied. Conduct basic statistical analyses (e.g., averages, stan­

dard deviations) and interpret the resulting data.

Narrative. Discrete Chl-a data have historically been collected

during oceanographic cruises, primarily from water sampled

throughout the water column using Niskin bottles mounted on

a CTD-Rosette. The general procedure for discrete Chl-a mea­

surements involves filtering a known volume of seawater to

retain all phytoplankton cells on the filter, extracting the Chl-a

retained on the filter with a solvent, and then quantifying the

amount of Chl-a in the solvent by fluorescence. Additionally,

high-performance liquid chromatography (HPLC) can be used

to quantify Chl-a concentration. These methods for sampling,

filtering, extracting, and quantifying are relatively simple and

can be performed as a lab activity, depending on resources avail­

able to students.

During NES-LTER cruises, discrete Chl-a samples for the

calibration of the underway fluorometers were collected from

a spigot connected to the underway system so that the samples

contained water that had just run through the two fluorometers

(Menden-Deuer et al., 2022). Additional discrete Chl-a samples

are routinely collected from the Niskin bottles mounted on the

CTD-Rosette at each sampling station at various depths (Sosik

et al., 2023), including at the surface (3–7 m depth). While these

additional data could be used to post-calibrate the underway

FIGURE 2. Examples of (a) underway raw fluorescence (in volts, V), and

(b) manufacturer calibrated fluorescence (mg Chl-a m–3) recorded by the

WetStar (dark green) and the ECOFl (light green) fluorometers vs. time

during the EN661 Northeast US Shelf Long-Term Ecological Research

(NES-LTER) cruise in winter 2021. (c) Difference of the manufacturer-​

calibrated fluorescence signals between the two fluorometers

(mg Chl-a m–3), with light green shaded area representing nighttime (here

defined from 7 p.m. to 7 a.m. local time).

Oceanography | Vol. 38, No. 2

78

fluorometers, we will focus here only on the discrete under­

way Chl-a data. Before collection, the date and time of sam­

pling were recorded along with the current fluorometer read­

ings. Fifteen to 20 samples were collected on a random timeline

during the cruise, while ensuring collection of half the samples

during the day and about half during the night, to capture the

effects of nonphotochemical quenching (Marra, 1998; Holm-

Hansen et al., 2000). Additional effort was devoted to maximiz­

ing the dynamic range of fluorescence and corresponding Chl-a

concentrations, based on real-time observations of the under­

way fluorescence signals (e.g., during periods of unusually low

or high fluorescence). A collection container with a volume

between 500 mL and 1 L was rinsed three times with underway

water, then filled. Three plastic 152 mL bottles were then filled to

the top with the underway water in triplicates. Immediately after

collection, the entire volume of each triplicate was filtered onto

Whatman GF/F 25 mm filters using gentle vacuum (not exceed­

ing 150 mm Hg) in a light-limited environment to avoid any

degradation of the Chl-a pigments. The filters were then each

placed in glass tubes containing 6 mL of 95% ethanol, capped,

and stored in the dark at room temperature to extract the Chl-a

for approximately 12 hours (±2 hours). After the extraction

period, the fluorescence of the samples was recorded with a

Turner 10AU fluorometer first as is, and then with the addition

of acid to correct for phaeopigments (Wasmund et al., 2006).

The discrete underway sample data were digitized and orga­

nized, then Chl-a concentration, in mg m–3 (= μg L–1), was cal­

culated using coefficients obtained from the in-lab fluorometer’s

calibration; this was performed before each cruise based on pure

Chl-a standards (Sigma-Aldrich, from Anacystis nidulans algae).

Each data point was then given a quality flag based on the IODE

(International Oceanographic Data and Information Exchange)

quality flag scheme (IOC, 2013) so that only the highest quality

data would be included in the post-calibration. Discrete under­

way Chl-a data from six NES-LTER cruises are available on the

EDI data portal (Menden-Deuer et al., 2022).

SECTION 2. USING DISCRETE CHL-a TO

POST-CALIBRATE SENSOR-BASED FLUORESCENCE

(1.5 hours)

There can be substantial differences between manufacturer-​

calibrated continuous fluorescence data and discrete Chl-a con­

centrations. Manufacturer-calibrated fluorescence values con­

verted to Chl-a concentrations (mg m–³) should be interpreted

with caution because the calibration is typically performed

using either pure Chl-a extracts or single-species phytoplank­

ton cultures that may not accurately reflect the local phyto­

plankton community, environmental conditions (e.g., tempera­

ture), or optical properties encountered in the field. Factors

such as species composition, physiological state, light his­

tory, and colored dissolved organic matter (CDOM) can all

influence the fluorescence signal independent of actual Chl-a

concentration. The optical components of the fluorescence sen­

sor may also be biofouled during deployment. Although this

is minimized by cleaning the sensors before and after each

deployment and by maintaining a high flow rate, any biofoul­

ing can still alter the recorded optical signal. As a result, with­

out cross-validation, these manufacturer-derived values can be

substantially different from in situ Chl-a. Therefore, it is crucial

to acknowledge, correct for, and interpret the uncertainty and

imprecision in in vivo fluorescence data to interpret the fluo­

rescence signal (Cullen, 1982; Falkowski and Kiefer, 1985; Xing

et al., 2017). To obtain reliable, accurate, high-resolution Chl-a

data from in vivo fluorescence, the continuous fluorometer data

must undergo post-​calibration against discrete Chl-a values.

The steps required for this data management are the subject of

this hands-on exercise.

PART 1. PLOTTING SENSOR-BASED CHL-a FLUORESCENCE

VS. EXTRACTED CHL-A CONCENTRATIONS

Goals. Linking sensor-based underway chlorophyll-a (Chl-a)

fluorescence and discrete Chl-a data. Introduce methods required

for post-calibrating sensor-based Chl-a fluorescence data.

Expected Outcomes. Develop familiarity with linear regres­

sion, including the concepts of slope, intercept, and coefficient

of determination. Understand the significance of linear regres­

sion results and their application in post-calibrating underway

Chl-a fluorescence data.

Narrative. It is now time to compare the discrete Chl-a concen­

trations with the corresponding underway fluorescence values

observed when sampling (Figures 3 and 4). The goal here is to

identify whether both fluorometers are equally well suited to use

for the post-calibration and to identify the coefficients that will

FIGURE 3. Raw underway fluorescence (mg Chl-a m–3) during the EN661

NES-LTER transect cruise (February 3 to February 7, 2021, winter in the

Northern Hemisphere) from the WetStar (dark green) and the ECO-Fl (light

green) fluorometers. The discrete Chl-a concentrations collected in tripli­

cate during the cruise are represented by black dots. Only discrete Chl-a

data with an IODE Quality Flag = 1 (good) are shown. Note the change in

fluorescence from the WetStar fluorometers on 02/05/2021, which cor­

responds to the change observed after the cleaning of the instruments.

June 2025 | Oceanography

79

Chl-a concentrations were generally higher in inner shelf

waters (northern half of the transect) than in the outer shelf

waters (southern half of the transect). This difference can be

attributed to the shallower depth and greater influence of coastal

inputs in the inner shelf region, which result in more nutrients

for phytoplankton growth. In contrast, the outer shelf waters are

more oligotrophic, similar to some open ocean regions.

During summer, nitrate (an essential nutrient for phyto­

plankton growth) is completely depleted in the surface waters

of the NES, indicating that phytoplankton growth is likely based

on remineralized nutrients through the microbial loop, favoring

the growth of small phytoplankton cells (Marrec et al., 2021).

However, in the summer of 2019, an intense bloom of large

FIGURE 4. Discrete Chl-a concentrations (mg m–3) plotted against

the matching fluorescence values from (a) the ECO-Fl fluorome­

ter (mg m–3), and (b) the WetStar fluorometer (mg m–3) during the

EN644 summer 2019 cruise (August). The green dashes repre­

sent the line of best fit from a model I linear regression, with the

equation, including the slope and intercept, shown as an insert

on each figure. The shaded green area represents the 95% confi­

dence interval obtained for the linear regression model.

be used for the post-calibration of the fluorometer. Some basic

statistical concepts such as linear regression will be introduced.

Note that on most oceanographic cruises, only one fluorome­

ter is available to record underway fluorescence, meaning that

selection of one of two fluorometers is not possible.

PART 2. POST-CALIBRATION TO ESTIMATE CHL-a

CONCENTRATION FROM IN VIVO FLUORESCENCE

Goals. Post-calibrate the underway fluorescence data by apply­

ing the relationships established in Section 2, Part 1, between

the raw fluorescence measurements and the discrete Chl-a con­

centration data. Compare the raw fluorescence values with the

post-calibrated data collected during the three summer cruises

and interpret the resulting figures.

Expected Outcomes. Gain insight into the significance of post-​

calibrating raw fluorescence data for analyzing the inter-​annual

variations in phytoplankton biomass within a highly dynamic

coastal ecosystem.

Narrative. After identifying the best suited fluorometer, the

goal is to apply the relationship obtained from the linear regres­

sion to the continuous underway measurements for each cruise

(Figure 2 and in online supplementary materials) and ulti­

mately to create a new data package that includes all these post-​

calibrated measurements to share with the scientific community.

We also present here an illustration of why post-calibration of

fluorescence data is essential (Figure 5) and invite the students

to interpret the results obtained by comparing post-calibrated

fluorescence among three summer NES-LTER cruises.

When looking at the data from the three summer NES-LTER

cruises together, the first observation is that the fluorescence sig­

nal in 2019 has a much higher magnitude and is more variable

and “noisy” compared to the signals from the summers of 2020

and 2021. Based on the raw fluorescence values, the concentra­

tion of Chl-a was higher, indicating higher phytoplankton bio­

mass in the surface waters of the NES in 2019 than in 2020 and

2021. Additionally, there seemed to be higher concentrations of

Chl-a in surface waters along the 2020 transect than in 2021.

The fluorescence signal in 2019 remains more variable and

higher than during the other two cruises after post-calibration.

Interestingly, while the raw fluorescence data suggested more

Chl-a in 2020 than in 2021, post-calibration revealed that the

Chl-a concentrations were actually very similar. This under­

scores the importance of post-calibration when comparing

fluorescence values from different cruises.

Some essential background information about the oceano­

graphic context of the NES may be helpful for instructors to inter­

pret the data obtained. To support this, we included an introduc­

tion to the seasonal dynamics of the phytoplankton community

in NES waters in a dedicated section of the Lab Instructions doc­

ument, available in the supplementary materials.

Oceanography | Vol. 38, No. 2

80

diatom cells was observed along the transect. This bloom was

comprised of nitrogen-fixing bacteria living in symbiosis with

a diatom species (Hemiaulus), providing the necessary nitrogen

that was not available as nitrate (Castillo Cieza et al., 2024).

We demonstrated that post-calibrating Chl-a fluorescence

values are essential for accurate comparison, as the calibration

substantially altered the estimated Chl-a concentrations. In this

study, we used fluorescence values from different cruises, where

fluorometers either underwent manufacturer calibrations or

were replaced by spare instruments of the same model. A similar

approach can be applied when comparing fluorescence values

from the same study area but obtained from different research

vessels or other platforms such as moorings, CTDs, or gliders.

Without proper post-calibration, raw Chl-a fluorescence values

cannot be reliably compared.

FEEDBACK FROM STUDENTS AND

RECOMMENDATION TO INSTRUCTORS

The exercise described here was repeatedly tested with stu­

dents in class and in self-paced assignments. The major feed­

back from students was that they struggled with obtaining the

data from online repositories in reproducible ways. Different

versions of the same spreadsheet tool interpreted dates and

number formatting differently. To accommodate these chal­

lenges—which could not easily be alleviated as students may

have many different software types and settings—we have

developed a more explicit step-by-step guide and provided

standardized files for each intermediary step, so students can

access properly formatted files for each step and can avoid lack

of data accessibility or formatting issues. These elements raise

awareness for students as they will certainly encounter similar

challenges related to data management in their own research

or classes. This requirement for troubleshooting often fosters

learning and confidence in the gained competency, as students

overcome obstacles and find solutions independently. As large-

scale open-access databases become increasingly prevalent, the

skills developed through this activity are essential and founda­

tional for many researchers.

STUDENT BENEFITS

Our proposed activity offers students a valuable opportu­

nity to better understand the limitations of relying on raw,

manufacturer-​calibrated Chl-a values, and more broadly, on

any biogeochemical data obtained from sensors. This serves

as a general example of working with calibrated instruments.

Data users may assume that fluorescence-derived Chl-a con­

centrations provided by manufacturers represent accurate and

true measurements of Chl-a and possibly by extension, biomass.

However, as demonstrated in this study, this is not the case.

This exercise shows students critical concepts in data valida­

tion and underscores the need for quality control by research­

ers. This is exemplified by differences between fluorometers with

varying specifications that can lead to discrepancies between

nighttime and daytime measurements (Figure 2c). These vari­

ations suggest that non-photochemical quenching (NPQ) of

Chl-a molecules occurs during daylight hours when light inten­

sity is high (Marra, 1998; Xing et al., 2012), with some instru­

ments being more sensitive to this process than others. Ideally,

FIGURE 5. (a) Map and bathymetry of summer (in Northern Hemisphere) NES-LTER transect cruises from August 2019 (EN644, green), July 2020 (EN655,

light green), and July 2021 (EN668, yellow) from Narragansett Bay, Rhode Island, to the shelf break. (b) Raw underway fluorescence (mg Chl-a m–3) from

each cruise vs. latitude (°N; note the reverse x-axis from higher latitudes in the north [left] to lower latitude in the south [right]). (c) Post-calibrated under­

way fluorescence (mg Chl-a m–3) vs latitude. For clarity, only data from the outbound leg of the transect (north to south) are shown.

June 2025 | Oceanography

81

only nighttime fluorescence data should be used for post-​

calibration, while daytime values should be corrected for NPQ

(Carberry et al., 2019). In our case, we show that the NPQ effect

is negligible for our post-calibration. Using discrete data, we

show that the relatively high variance in our calibration is likely

due to the inclusion of both daytime and nighttime data.

Students also engaged with the importance of clarifying what

an instrument measures and what the measurement represents.

The concept of C:Chl ratios is fundamental in biomass assess­

ments in oceanographic studies and plays a key role in student

learning outcomes by highlighting how data or model estimates

are influenced by the conversion factors used. We encourage

educators to engage students in discussions on the deep Chl-a

maximum (DCM) in oligotrophic waters and the effects of

photo­acclimation on cellular Chl-a content. The DCM has often

been interpreted in scientific literature and textbooks as a bio­

mass maximum. However, it primarily reflects photoacclima­

tion processes and variations in the C:Chl-a ratio (Mignot et al.,

2014; Cullen, 2015; Maranon et al., 2021). This serves as a crucial

example of why Chl-a should be used with caution as a proxy for

phytoplankton biomass.

Lastly, and this is our central topic, our goal was to empower

students with the formal tools of data science, data manage­

ment, and FAIR practices. A career in data science and man­

agement can represent a career pathway in itself or a bridge to

other professional opportunities for students. Expertise in data

science is highly transferable and can be applied across a wide

range of professional fields, within sciences and beyond. A nota­

ble example is Amanda Herbst, a coauthor of this study, who

after completing a summer internship using the skills covered

here, pursued a Master of Environmental Data Science degree

at the Bren School of Environmental Science and Management

at the University of California, Santa Barbara, and who recently

accepted a position as Environmental Analyst for the New

England Interstate Water Pollution Control Commission

(NEIWPCC) and will be working at the New York State

Department of Environmental Conservation.

Students are exposed to the vast universe of freely available

data and how to handle them. When sourced from data portals

with rigorous quality control procedures and well-documented

metadata, these datasets can be valuable resources for research

and analyses at minimal cost. Many students, researchers, and

institutions face financial constraints when conducting field

studies, which often require expensive platforms (e.g., research

vessels) and instrumentation (e.g.,  biogeochemical sensors).

By increasing awareness of existing high-quality, open-access

datasets, the oceanographic community could make signifi­

cant advancements. In fact, some long-term observational data­

sets remain underutilized despite being collected, processed,

and stored following state-of-the-art standards (e.g., NSF Dear

Colleague Letters 2024). Leveraging these resources could

greatly enhance our understanding of oceanographic processes.

CONCLUDING REMARKS

The main goal of this contribution to Oceanography’s Ocean

Education article category is to emphasize to students the

importance of proper handling and sharing of post-calibrated

data by publishing it in open-access data portals. All the data

used in this hands-on activity are openly available, allowing

researchers worldwide to access and utilize them. However,

as demonstrated, interpreting raw Chl-a fluorescence has lim­

itations. Therefore, providing the scientific community with

high-quality post-calibrated Chl-a fluorescence data is essential

for advancing research.

An important aspect of sharing high-quality data in open-​

access repositories is to include all information necessary for

understanding how the data were acquired and analyzed. This

additional information, known as metadata, includes intel­

ligible and descriptive data product names, precise tempo­

ral and spatial coverage, accurate and complete lists of science

keywords, and concise yet readable descriptions of the data

products. Instrument calibration documentation (e.g.,  man­

ufacturer calibration) and data analysis workflows are also

crucial metadata components. Publishing open-access data

packages following FAIR principles ensures that the science

is open, transparent, accessible, inclusive, and reproducible

(Wilkinson et al., 2016).

In our case, we created an EDI data package that compiles

post-calibrated underway fluorescence data for six NES-LTER

cruises, spanning from summer 2019 to summer 2021, as part of

coauthor Amanda Herbst’s summer 2021 REU project. The REU

research project included all aspects of the research this exer­

cise drew on, including cruise participation to acquire calibra­

tion data. The NES-LTER Information Management team sup­

ported us in the creation of this data package (Menden-Deuer

et al., 2022). Essential steps in creating a data package include a

clear description of the methods used to process the data, data

quality checks, and additional metadata to improve findability.

These steps benefited greatly from the experience of data man­

agers, who play an essential role in modern research projects.

Please note that publishing the data package is not included in

this activity, as all sample data are already published, and multi­

ple publications of the same data package are not desirable.

SUPPLEMENTARY MATERIALS

The supplementary materials are available online at https://doi.org/10.5670/

oceanog.2025.314.

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ACKNOWLEDGMENTS

This work was supported by awards from the National Science Foundation

(NES-LTER Phase 1: OCE-1655686, NES-LTER Phase 2: OCE-2322676). AH was

supported by a Summer Undergraduate Research Fellowship in Oceanography

(SURFO; National Science Foundation REU grant # OCE- 1757572). Support

through the NASA campaign EXport Processes in the global Ocean from RemoTe

Sensing (EXPORTS; grant 80NSSC17K0716) is acknowledged. We thank the stu­

dents, staff and PIs of the NES-LTER project for their support, and the leadership

of Heidi Sosik (Woods Hole Oceanographic Institution). We thank the captains

Armanetti, Beuth, and Carty, the R/V Endeavor Crew, and the work of the marine

technicians at the University of Rhode Island. Brian Heikes, David Smith, and

Jamie Buck are acknowledged for all the effort they put into the SURFO program.

We appreciated the enthusiasm and effort of the University of Rhode Island stu­

dents in the Graduate School of Oceanography class OCG561 (2024), who tested

this lab activity and substantively improved the final product.

AUTHORS

Pierre Marrec (pmarrec@uri.edu), Graduate School of Oceanography, University

of Rhode Island, Narragansett, RI, USA. Amanda Herbst, Graduate School of

Oceanography, University of Rhode Island, Narragansett, RI, USA, and Bren School

of Environmental Science & Management, University of California, Santa Barbara,

CA, USA. Stace E. Beaulieu, Woods Hole Oceanographic Institution, Woods Hole,

MA, USA. Susanne Menden-Deuer, Graduate School of Oceanography, University

of Rhode Island, Narragansett, RI, USA.

ARTICLE CITATION

Marrec, P., A. Herbst, S.E. Beaulieu, and S. Menden-Deuer. 2025. Hands-on

post-calibration of in vivo fluorescence using open access data: A guided jour­

ney from fluorescence to phytoplankton biomass. Oceanography 38(2):73–82,

https://doi.org/10.5670/oceanog.2025.314.

COPYRIGHT & USAGE

This is an open access article made available under the terms of the Creative

Commons Attribution 4.0 International License (https://creativecommons.org/

licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and repro­

duction in any medium or format as long as users cite the materials appropriately,

provide a link to the Creative Commons license, and indicate the changes that

were made to the original content.

June 2025 | Oceanography

83

THE OCEANOGRAPHY CLASSROOM

TAP

TEACHING ANALYSIS POLL FOR STUDENT FEEDBACK

By Robert Kordts, Mahaut de Vareilles, Kjersti Daae, Eirun Gandrud, Anne D. Årvik, and Mirjam S. Glessmer

Many university instructors receive end-of-semester responses

to standardized student questionnaires (student evaluations of

teaching, SETs) collected through online systems. But how well

do SETs work to improve teaching and student engagement in

learning? Research has found a large number of challenges and

problems with SETs, including, (1) they do not assess teaching

quality; (2) they often use quantitative, predefined scales that

leave little space for additional comments; (3) they often have

unclear goals, with course improvement not being the main one;

and (4) there is often little student engagement, indicated by low

response rates for online evaluation.

At the Geophysical Institute (GFI), University of Bergen

(UiB), we consider high-quality feedback from students to

instructors important in order to improve course outcomes.

However, we wanted to move away from SETs and so looked

for alternative feedback methods that would better represent

student views (respecting both their qualitative and quanti­

tative aspects) and could be presented to the instructors in a

motivating way.

We chose to experiment with the Teaching Analysis Poll

(TAP; Hawelka, 2019) that was, to our knowledge, developed

at the University of Virginia and has been used in different

higher-education institutions, countries (e.g., United States,

Germany, Switzerland), and disciplines. The recommended

TAP procedure for face-to-face classes takes about 30 minutes

and is performed by an external facilitator who collects student

feedback on three aspects, which are then communicated back

to the class instructor:

1. Which aspects of the course facilitate your learning?

2. Which aspects of the course hinder your learning?

3. What suggestions do you have for improving the obstructive

aspects?

Box 1 provides a detailed description of the TAP procedure as

employed by the authors.

The method can easily be adapted to different teaching sit­

uations. As facilitators, we have experience with TAP in both

small courses with two or three student groups and very large

courses with several hundred students; both face-to-face and

online (using online collaborative writing and poll tools); and

with both TAP on the course level and TAP on the study-​

program level (with students commenting on aspects related

to the program curriculum). See the variants described in

Johannsen and Meyer (2023).

At GFI, TAP implementation was part of a larger educa­

tion initiative, iEarth Center for Integrated Earth Science

Education, and of an ongoing collaboration with the UiB uni­

versity pedagogy group. Between 2022 and 2024, we conducted

seven TAPs in selected geoscience courses (many of which had

a focus on active learning), and two courses repeated the TAP

after one year. People involved were administrative staff at GFI,

a university pedagogy colleague, and two students who served

as TAP co-facilitators and helped analyze the data.

Because one of TAP’s characteristics is confidentiality, we

will not detail TAP results. However, to provide an overview

of the topics mentioned, we analyzed all TAP reports based

on the categories identified by Hawelka (2019). Hawelka’s sys­

tem includes eight main categories and several subcategories,

ranging from comments about interactions between students

and instructors to students’ understanding of the task, their

motivation, their learning strategies, and their self-regulation

for learning, to general resources and overall ratings about

the course and about its structural conditions. Table 1 shows

samples of the Hawelka (2019) categories that appeared most

often in the TAPs together with examples of students’ positive

or negative quotes.

TAP results provide not only general positive or nega­

tive views (Category No. 7) but also comments on more spe­

cific points, such as the learning materials (Category 6.2) or the

lecturer’s presentation style (Category 1.1). In fact, most com­

ments found in the TAP were about aspects that the instruc­

tors typically can change. Rather surprising to us, the students

commented on aspects that support their learning progress

(Category 5.2), specifying positive and critical examples. This

indicates that the TAP stimulates the students to evaluate what

others, such as the instructors, do, as well as what they need for

their own learning success. This is a huge advantage of the TAP

compared to traditional SET methods. Finally, some TAP feed­

back relates to aspects that instructors alone typically cannot

change (Category 8).

Oceanography | Vol. 38, No. 2

84

BOX 1. TEACHING ANALYSIS POLL (TAP)

AT THE GEOPHYSICAL INSTITUTE, UNIVERSITY OF BERGEN

Getting Constructive Student Feedback for Interim Course Improvement

We find the TAP method particularly useful because of the limited investment and effort it requires, it represents anonymized

students views (while respecting both their quantitative and qualitative aspects), and it provides constructive feedback to the

instructor midway through the course in a motivating and actionable way.

In the hope that more courses apply this method, we share a step-by-step description, with practical tips, of how we imple­

ment TAP. For further information and other examples of TAP implementation, we recommend starting with Hawelka (2019) and

Johannsen and Meyer (2023).

STEP 1. Find a Facilitator to Conduct the Tap

The facilitator is the person who will conduct the poll with the students in the absence of the instructor and report the student

feedback to the instructor after the poll. It is important that this person is neutral, that is, has no conflict of interests with either

instructor or students. The facilitator should be familiar with the TAP method but does not necessarily need to be an educator.

Indeed, at GFI, the TAPs have worked well when performed by the research advisor (administrative staff) or students external to

the course.

The facilitator and instructor then agree on a time to conduct the TAP. We typically choose 20–30 minutes at the end of a class,

midway through the course. Though time is valuable to instructors and students alike, our experience at GFI is that both instruc­

tors and students who have been part of a TAP found it worth their time, with several instructors requesting TAPs in following

years. Holding the TAP toward the end of a class period is helpful because the students are already in place with their minds

fresh on the topic.

STEP 2. Student Group Discussions (10–15 min)

After the instructor has left, the facilitator briefly explains the purpose and procedure of a TAP and asks the students to form small

groups of three to five students. Feedback from up to five groups is usually representative of the majority student view, so for

large class sizes, we recommend taking a random sample of five student groups.

The groups are asked to discuss and collaboratively fill out a form (paper or online) that contains the following three questions

(this takes about 10 minutes):

1. Which aspects of this course facilitate your learning?

2. Which aspects of this course hinder your learning?

3. What suggestions do you have for improving the obstructive aspects?

STEP 3. Polling (10–15 min)

The facilitator collects the forms, reads them aloud to all, solicits clarification where needed, and asks the students to raise their

hands if they support a statement. We have found that for very small classes (e.g., only two groups), it might be worth asking stu­

dents to vote in a more anonymous way to avoid having peer pressure influence the vote. We stress the importance of making

sure that any unclear statement is fully understood by all before voting. For example, a statement such as “instructor talks too

fast” could mean there is a language/communication issue, or it could mean that the amount of content planned for one single

class is too large. It is important to clarify such aspects so the instructor can better work with the feedback.

STEP 4. Feedback and Analysis

After the TAP, the facilitator meets with the course instructor to discuss the anonymized student feedback (and potential conclu­

sions), focusing on statements that received support from 50% or more of the students.

In our experience, the meeting between the facilitator and instructor usually suffices for the instructor to be able to work on

the feedback towards improving teaching and learning in the class. However, we also offer the possibility for the instructor to

schedule a meeting with staff at the university pedagogy group should they feel better guidance is needed for addressing some

issues. The instructors are responsible for telling their students what they have learned through the TAP. Additionally, instructors

should explain which aspects they can and will change, which they will not change, and provide rationale for their decisions.

June 2025 | Oceanography

85

We believe that instructors should respond to a TAP session

by telling their students what they learned from it. Additionally,

they should explain to students which aspects they can and will

change, as well as those they will not, providing the rationale

for their decisions. In our specific case, forwarding some of the

student feedback to the study administration led to some struc­

tural improvements, such as better equipment in classrooms.

The feedback we received from the instructors was all positive—​

important, considering that they had to invest 30 minutes of

their valuable class time to administering the TAP.

If you are interested in trying out TAP as a feedback

method, we recommend aligning your evaluation approach

with the instructors’ and study programs’ needs and goals.

The TAP could be part of a larger transformation pro­

cess that could also, for instance, include introducing active

learning or alternative teaching methods. To gain experi­

ence with TAP, it is useful to employ two facilitators, to start

small with a few courses, and then to build a team of people

who can facilitate TAPs. Because staff time is often limited,

TAP facilitators could include students, which is something

we have done and have found to work well. We know of at

least one university (University of Erlangen-Nuremberg) that

trains students to be TAP facilitators. Working together with

students in this way is a great example of student-staff part­

nership and co-creation. Feel free to contact us to discuss TAP

(https://cocreatinggfi.w.uib.no/contact/).

REFERENCES

Hawelka, B. 2019. Coding Manual for Teaching Analysis Polls. University of

Regensburg: Center for University and Academic Teaching (ZHW), https://www.

uni-regensburg.de/assets/zentrum-hochschul-wissenschaftsdidaktik/forschung/

manual-tap-2019.pdf.

Johannsen, T., and H. Meyer. 2023. Improving Teaching Quality In Higher

Education: A Practitioner’s Guide To Using Formative Teaching Analysis Poll.

European Society for Engineering Education (SEFI), https://doi.org/​10.21427/​

8REM-2V61.

AUTHORS

Robert Kordts (robert.kordts@uib.no), Mahaut de Vareilles, Kjersti Daae,

Eirun Gandrud, Anne D. Årvik, and Mirjam S. Glessmer, University of Bergen,

Bergen, Norway.

ARTICLE CITATION

Kordts, R., M. de Vareilles, K. Daae, E. Gandrud, A.D. Årvik, and

M.S. Glessmer. 2025. TAP: Teaching Analysis Poll for student feedback.

Oceanography 38(2):83–85, https://doi.org/10.5670/oceanog.2025.305.

COPYRIGHT & USAGE

This is an open access article made available under the terms of the Creative

Commons Attribution 4.0 International License (https://creativecommons.org/

licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and repro­

duction in any medium or format as long as users cite the materials appropriately,

provide a link to the Creative Commons license, and indicate the changes that

were made to the original content.

TABLE 1. Relevant categories from Hawelka (2019) identified in GFI TAP, 2022–2024. The first and second columns indicate the category titles, number

of responses (n), and definitions. The third and fourth columns show example GFI TAP responses in each category.

CATEGORY TITLE

CATEGORY DEFINITION

EXAMPLE RESPONSES TO THE QUESTIONS…

WHAT FACILITATES LEARNING?

WHAT HINDERS LEARNING?

Learning Materials, 6.2

(n = 22)

The lecturer provides helpful learning

resources for self-study.

“the [Learning Management System’s]

page is tidy”

“[we want] more exam-relevant

problems”

Presentation, 1.1

(n = 16)

Lecturers use adequate rhetoric

and visual means to present the

learning material in an intelligible and

stimulating way.

“[Instructor] is very good at explaining

concepts in a pedagogical way”

“[Instructor should] talk slower and

clearer”

Monitoring students’

learning progress, 5.2

(n = 13)

The teacher supports the students

in monitoring their learning progress

through feedback, formative

assessment, and similar strategies.

“Quiz at the end of lecture”

“The lab report seems to be more

work than learning”

General framework, 8

(n = 12)

This category includes all feedback

about the course, the lecturer, and

learning outcomes.

“The small size of the class”

“Classroom: Screens are hard to see,

some screens do not work”

Overall rating, 7

(n = 11)

This category includes the

organizational and curricular

framework of the course.

“Good introduction to different

courses that come later in program”

“Workload of this course more like

10 ECTS than 5”

Oceanography | Vol. 38, No. 2

86

BOOK REVIEW

A PHILOSOPHICAL VIEW

OF THE OCEAN AND HUMANITY

SECOND EDITION

Book by Anders Omstedt, 2024, Springer Cham, 178 pp., ISBN (hardcover): 978-3-031-64325-5,

ISBN (eBook): 978-3-031-64326-2, https://doi.org/10.1007/978-3-031-64326-2

Reviewed by Emma Coleman

Anders Omstedt is a Swedish oceanographer, author, and

professor emeritus in the Department of Marine Sciences,

University of Gothenburg. The second edition of his book enti­

tled A Philosophical View of the Ocean and Humanity, published

in 2024, is heavily influenced by the United Nations Decade of

Ocean Science for Sustainable Development (2021–2030). In

33 short chapters, Omstedt explores an array of topics spanning

oceanography, philosophy, and science communication. Despite

the broad nature of the topics, he always returns to probe the cen­

tral relationship between humans and the ocean. From promot­

ing the power of dreams as a key tool for creatively imagining

the future to giving succinct overviews of the major challenges in

ocean science today, Omstedt maintains an interesting conversa­

tion with the ocean throughout the book, recognizing it as a part­

ner with an active role to play in changing human behavior.

This second edition is divided into three sections. Parts  I

and III are entirely new. The first edition, published in 2020, is

present in a largely rewritten form in Part II. The second edition

also includes new illustrations along with forewords by Bernt

Gustavsson, Örebro University, and Markus Meier, Leibniz

Institute for Baltic Sea Research Warnemünde. The new content

adds necessary depth to the book, and I encourage readers to

engage with the updated edition.

In Part I, Omstedt “illustrate[s] how analytical thinking and

intuition can be trained by observing how we think and feel”

(p. 3). Here poetry, art, and dreams are introduced as tools that

can support and foster scientific curiosity and discovery. Omstedt

explores the merits of creative thinking in the Anthropocene and

highlights the insights these tools offer in the face of global chal­

lenges. Part II outlines “the threats the ocean faces through var­

ious human activities…[and the need to] work across many

academic disciplines, using transdisciplinary approaches and

developing new skills for conversation” (p. 129). Two perspec­

tives are interwoven throughout Part II. One gives an analyti­

cal overview of ocean science problems, and the other is repre­

sented by an intuitive conversation between a marine scientist

and the ocean. By paralleling these seemingly disparate modes of

thinking, readers are given an example of how both scientific and

artful inquiry work together to reframe our understanding of the

ocean and ourselves. Finally, Part III “deepens the description of

humans’ relationship to the ocean and our way of thinking with

inspiration from literature and philosophy” (p. xiii). In this sec­

tion, Omstedt grounds the ideas and cognitive tools introduced

in Parts I and II by complementing analytical research with the

insights gained from engagement with art and literature.

Throughout A Philosophical View of the Ocean and Humanity,

scientific and spiritual stories are combined to encourage changes

in human behavior. Omstedt asks the reader to meditate on ques­

tions about Earth and its ocean, as well as about life and our place

in it. In addition to scientific facts, Omstedt draws from mythol­

ogy, song, and novels, weaving together a story of the ocean and

humanity. Through this weaving, the book provides a multi­

faceted reading experience that challenges traditional Western

scientific paradigms by embracing critical reflection, personal

feelings, and creative thinking. Readers may be fascinated with

the oceanography-based chapters of Part  II or resonate more

closely with the dreamscapes illustrated in Part I. Thus, this book

is suited to a wide audience, as it pieces together creative and log­

ical ways of knowing in a broad meditation on the ocean and

humanity, one that opens new avenues of thought for change­

making. Oceanographers, climate scientists, science writers, and

scholars of science and technology studies may find the content

of this text particularly useful for informing their own work.

Omstedt makes it clear that ways of being and knowing out­

side of traditional science paradigms are necessary—not only for

enriching human lives, but for doing better science. He uses clear

language when articulating his philosophy. Omstedt avoids mak­

ing technical recommendations and focuses instead on human

understanding of the ocean on a philosophical level, and par­

ticularly, how that understanding shapes the practice of science.

It is a push that is especially useful for today’s oceanographers

and climate scientists who are pursuing their research in increas­

ingly unstable times. Taking the time to consider and commit

(or recommit) to the ethical and philosophical underpinnings

June 2025 | Oceanography

87

of one’s research is a worthwhile process because it engenders

a deeper understanding of the necessary network of support.

Furthermore, expanding one’s network to include non-​human

actors like the ocean can, as Omstedt emphasizes, reorient

research in a direction that more closely aligns with actual change.

Although science provides one set of methodologies for

investigating and understanding the physical world, it does not

always have the best tools for influencing or changing human

behavior in the context of global crises. In chapter 10, for exam­

ple, Omstedt interrogates human understanding of intelligence

through an exploration of art and dreams. Omstedt’s analy­

sis of unconscious knowledge is reminiscent of cognitive lin­

guist George Lakoff’s understanding of framing. Lakoff points

out that “real reason is mostly unconscious (98%) [and] requires

emotion…ideas and language can’t directly fit the world but

rather must go through the body” (Lakoff, 2010, pg. 72). It is

critical for scientists and science writers to consider the felt or

embodied experience, especially when attempting to under­

stand or change human behavior. Rethinking how we motivate

change is now more important than ever, given the ever esca­

lating effects of climate change (Tollefson, 2025). No single sci­

entific discipline holds all the knowledge needed for under­

standing the many facets of climate change, nor does Western

science as a whole. There is increasing recognition that the tools

humanity needs for mitigating and adapting to a changing cli­

mate will come from diverse sources, including STEM, social

sciences (Dudman and de Wit, 2021; Berg and Lidskog, 2024),

Traditional Ecological Knowledge (Kimmerer, 2012), and the

co-production of knowledge (Jasanoff, 2021).

Knowledge production outside of disciplinary divides is

not new in the field of oceanography, which has embraced

interdisciplinary collaboration since its foundation. The

Intergovernmental Oceanic Commission (IOC) was created in

1960 during the 11th general conference of the United Nations

Educational, Scientific, and Cultural Organization (UNESCO)

(UNESCO, 1961). The IOC facilitates communication and col­

laboration among member states regarding oceanic and coastal

management and research initiatives. Former IOC Executive

Secretary Gunnar Kullenberg writes about the history of ocean

science in his 2020 book, Ocean Science and International

Cooperation: Historical and Personal Reflections. This text

would complement Omstedt’s by providing readers with addi­

tional historical context for the expansive and interdisciplin­

ary research methods for which he advocates. Today, one way

collaboration can be seen is through the US National Science

Foundation’s Ocean Observatories Initiative, which shares real-

time data from hundreds of instruments. As Levine et al. (2020)

explain, the democratization of these data presents opportuni­

ties for oceanographers, especially those early in their careers, by

increasing data access. The equity these initiatives provide allows

more scientists to actively engage with the ocean as a research

partner. Collaborative research, including the Challenger, Vega,

and Albatross expeditions that Omstedt highlights, are essential

parts of oceanographic history. Omstedt advocates not only for

the continuation but the expansion of this legacy.

A Philosophical View of the Ocean and Humanity contains

many short chapters and, due to the brevity of each, the book

is best suited for readers who have some background in science,

oceanography, or communication studies. The book spends less

time interrogating the finer details of ocean science research

and reads more broadly as a rethinking of the field’s underlying

ontology and epistemology. Readers may find the structure of

this book (especially Part I) surprising, but it offers a rich oppor­

tunity for thoughtful discussion and reflection. The discussion

questions at the end provide direction for future engagement,

and thus the book would be particularly well suited for use in

an upper-level undergraduate or graduate classroom setting

where its content may be analyzed in the context of other ocean­

ographic or science and technology studies literature.

In addition to being a book about science, oceanography,

and dreams, this book is also about science communication as it

explores what kinds of thinking, discussion, and action are nec­

essary for changing human behavior. At times, the brief chap­

ters limit some nuance, but when read collectively, strong central

themes emerge that make this a book worth reading. Omstedt

interrogates the philosophical relationship between humanity

and the ocean by weaving together different kinds of understand­

ing, from scientific expeditions to art and dreams. With half of the

UN Ocean Decade behind us, Omstedt’s book provides encour­

agement to slow down and reflect upon our relationship with the

ocean so that we can make the most of what time remains.

REFERENCES

Berg, M., and R. Lidskog. 2024. Global environmental assessments and trans­

formative change: The role of epistemic infrastructures and the inclusion of

social sciences. Innovation: The European Journal of Social Science Research,

https://doi.org/​10.1080/13511610.2024.2322642.

Dudman, K., and S. de Wit. 2021. An IPCC that listens: Introducing reciprocity to cli­

mate change communication. Climatic Change 168(2), https://doi.org/10.1007/

s10584-021-03186-x.

Jasanoff, S. 2021. Knowledge for a just climate. Climatic Change 169(36),

https://doi.org/10.1007/s10584-021-03275-x.

Kimmerer, R.W. 2012. Searching for synergy: Integrating traditional and scien­

tific ecological knowledge in environmental science education. Journal of

Environmental Studies and Sciences 2(4):317–323, https://doi.org/10.1007/

s13412-012-0091-y.

Lakoff, G. 2010. Why it matters how we frame the environment. Environmental

Communication 4(1):70–81, https://doi.org/10.1080/17524030903529749.

Levine, R.M., K.E. Fogaren, J.E. Rudzin, C.J. Russoniello, D.C. Soule, and

J.M. Whitaker. 2020. Open data, collaborative working platforms, and interdis­

ciplinary collaboration: Building an early career scientist community of practice

to leverage Ocean Observatories Initiative data to address critical questions in

marine science. Frontiers in Marine Science 7:593512, https://doi.org/10.3389/

fmars.2020.593512.

UNESCO. 1961. Records of the General Conference, 11th session, Paris, 1960:

Resolutions. 250 pp., https://unesdoc.unesco.org/ark:/48223/pf0000114583.

Tollefson, J. 2025. Earth breaches 1.5°C climate limit for the first time: What does it

mean? Nature 637(8047):769–770, https://doi.org/10.1038/d41586-025-00010-9.

REVIEWER

Emma Coleman (ecoleman1@esf.edu), State University of New York College of

Environmental Science and Forestry, Syracuse University, Syracuse, NY, USA.

ARTICLE DOI

https://doi.org/10.5670/oceanog.2025.312

Oceanography | Vol. 38, No. 2

88

CAREER PROFILES Options and Insights

Degree: When, where,

what, and what in?

I hold a bachelor’s degree in

oceanography (2004) from the

Federal University of Paraná,

Brazil; a master’s degree in

remote sensing (2008) from

the National Institute for Space Research, Brazil; a postgraduate

specialization in observational oceanography (2010) from the

Nippon Foundation-Partnership for Observation of the Global

Ocean (NF-POGO) Centre of Excellence in Observational

Oceanography at the Bermuda Institute of Ocean Sciences,

Bermuda; and a doctorate in marine and environmental sci­

ences (2018) from the University of Algarve, Portugal.

Since my undergraduate studies, I have worked on various

applications of satellite remote sensing and modeled data to

ocean and coastal research, including shallow water bathymetry,

coral bleaching prediction, sea-air CO2 exchange, and phyto­

plankton phenology and variability, as well as their environ­

mental drivers.

Did you stay in academia at all, and if so, for how long?

I remained in academia throughout my education and profes­

sional development until I completed my PhD in 2018. My aca­

demic journey began in 2001 with an internship during my sec­

ond year as an undergraduate. During all this time, I alternated

between roles as a student and a research assistant—often bal­

ancing both simultaneously—gaining experience in both funda­

mental research and applied science.

How did you go about searching for a job outside of

the university setting?

For me, the transition happened quite naturally. During my

time at the NF-POGO Centre of Excellence, I had the opportu­

nity to learn from and work alongside Trevor Platt and Shubha

Sathyendranath, who were leading the POGO Secretariat at the

time. Shortly after completing the program, they invited me—

along with a few other former scholars—to explore the idea of

creating an alumni network, which later became NANO (the

NF-POGO Alumni Network for the Ocean, https://nf-pogo-​

alumni.org/).

Lilian (Lica) Krug, Scientific Coordinator, Partnership for Observation

of the Global Ocean (POGO), Centro de Ciências do Mar do Algarve

(CCMAR) – Campus de Gambelas, University of Algarve, Faro, Portugal

(lakrug@ualg.pt)

I initially worked on NANO remotely from Brazil, with a

small fellowship, helping to establish its foundation—building a

database, website, and newsletter, and connecting with alumni.

The following year, I moved to Portugal for a research assis­

tant position and began my PhD studies. My involvement with

NANO continued part-time because I was so invested in it—

it felt like my “baby”! Over time, I became deeply embedded in

POGO’s capacity development activities, and it felt like a natural

aspiration to one day join the POGO Secretariat team.

When the position of Scientific Coordinator became avail­

able around the time I completed my PhD, I was encouraged

to apply. My experience with NANO and capacity development,

along with my background in ocean science, positioned me well

for the role.

Is this the only job (post-academia) that you’ve had?

If not, what else did you do?

Yes. My other engagements with ocean science capacity devel­

opment are also very much entangled with POGO and NANO.

Between 2015 and 2024, I contributed as an instructor at the

Centre of Excellence, and since 2021, I have been a volun­

teer member of the Trevor Platt Science Foundation (TPSF)

Secretariat, an Indian not-for-profit that aims to continue

Platt and Sathyendranath’s amazing work in capacity devel­

opment for early career ocean professionals from low-income

countries. My main activity at TPSF is to coordinate its online

mentorship program.

What is your current job? What path did you take

to get there?

I am the scientific coordinator for POGO. In this role, my

responsibilities include coordinating our training programs and

other capacity development activities, including NANO, liaising

with members and partner institutions, and managing inter­

actions with trainees and alumni. I also represent the organiza­

tion at scientific and high-level events.

My journey to this position began with my involvement in

NANO, where I gained experience in network-building, project

coordination, and ocean science advocacy. This, combined with

my academic background, allowed for a seamless transition into

my current role.

June 2025 | Oceanography

89

What did your oceanographic education (or academic

career) give you that is useful in your current job?

My academic training provided me with a strong foundation in

observational oceanography, along with technical skills in sci­

entific writing, data analysis, and project management. Equally

important were the practical and soft skills I developed, such

as public speaking, networking, and communicating science to

diverse audiences—all of which are crucial in my current role.

Is there any course or other training you would have

liked to have had as part of your graduate education to

meet the demands of the job market?

While my education thoroughly prepared me for the scientific

aspects of the job, I would have benefited from formal train­

ing in project management, leadership, and public engagement.

These skills are essential for coordinating large-scale initiatives,

managing teams, and effectively communicating ocean science

beyond academia.

Is the job satisfying? What aspects of the job do

you like best/least?

Absolutely. As an early career ocean professional from a devel­

oping country, I know first-hand how transformative training

programs and fellowships can be. My favorite part of the job is

creating similar opportunities for others, knowing the impact

they can have. I review every application we receive very care­

fully, fully aware—through my own experience—of how these

opportunities can shape careers. I also love meeting our trainees

and staying in touch with them later through NANO.

The aspect I enjoy the least is the volume of administrative

work and reporting. While essential, these tasks can sometimes

be time-consuming and take time away from more engaging

aspects of my role.

Do you have any recommendations for new grads

looking for jobs?

Make the most of every learning opportunity—whether through

internships, volunteering in a university lab, or engaging in out­

reach and extension activities. Start building your professional

network early by connecting with mentors, attending events,

and exploring opportunities beyond traditional academia. These

experiences will help strengthen your CV and make it more

compelling. Oceanography is a vast field that offers many excit­

ing and unexpected career paths—stay open to new possibilities!

ARTICLE DOI. https://doi.org/10.5670/oceanog.2025.307

Degree: When, where, what, and

what in?

I earned a bachelor’s degree in ocean­

ography in 2004 from the Federal

University of Paraná (UFPR) - Brazil,

followed by a master’s degree in zool­

ogy in 2008 at the same university.

I completed my PhD in biological

oceanography in 2013 at the Federal

University of Pernambuco (UFPE),

Brazil. Throughout my academic jour­

ney, my research focused on the con­

servation of marine animals, particu­

larly sea turtles.

Did you stay in academia at all, and if so, for how long?

Although I’ve always appreciated the academic environment,

my involvement was limited to the time between my undergrad­

uate studies and completion of my PhD. Throughout this period,

I was fully engaged in research and academic life. However, I

was also drawn to outreach and science communication activi­

ties, which eventually inspired me to explore professional paths

beyond academia.

Flávia M. Guebert, Director, Coral Vivo Project, Coral Vivo Institute,

Santa Cruz Cabrália, Bahia, Brazil (flavia.guebert@coralvivo.org.br)

How did you go about searching for a job outside of the

university setting?

In truth, I never waited for a formal transition—I was already

building bridges outside academia while still a student. During

my undergraduate years, I helped create a small marine animal

rehabilitation center on campus to care for injured sea turtles.

I later met my graduate advisor, who was also president of an

environmental NGO, and I immediately became fully engaged

with the group’s initiatives—offering training courses, receiv­

ing interns (including international students), and organizing

immersion programs based on my practices.

Still as an undergraduate, I proposed and established a line of

research and outreach at my university that focused on marine

wildlife conservation, engaging other students and building

connections between science and society.

Later, during my PhD in the northeast of Brazil, I expanded

my focus to include human dimensions of conservation—study­

ing fishing practices, turtle poaching, and the role of protected

areas in coastal communities.

After completing my doctorate, I took a brief pause with the

birth of my first daughter. But soon after, I applied for a coordi­

nator position in one of Brazil’s leading coral reef conservation

NGOs. Following a long and competitive process, I was pleased

to be selected.

Oceanography | Vol. 38, No. 2

90

Is this the only job (post-academia) that you’ve had? If

not, what else did you do?

I’ve been working at the Instituto Coral Vivo ever since. I ini­

tially joined the team as a regional coordinator, managing the

Bahia hub of the Coral Vivo Project. After two years, I was

invited to take on the role of project director, and since then

have led national-scale initiatives and multidisciplinary teams

focused on advancing marine conservation in Brazil through

science, outreach, and collaborative networks.

What is your current job? What path did you take

to get there?

For the past eight years, I have had the honor of serving as direc­

tor of the Coral Vivo Project, a national-scale marine conser­

vation initiative that began in 2003. Coral Vivo takes a socio­

environmental and ecosystem-based approach to conserving

the coral reefs located off the northeast and southeast coasts of

Brazil, emphasizing six integrated axes: Scientific Knowledge,

Public Awareness, Public Policy, Social Impact, Socioeconomics,

and Conservation.

My path to this role was shaped by my early experiences in

field research and outreach, my commitment to inclusive con­

servation, and my belief in the power of science to inform and

mobilize. At Coral Vivo, we aim to raise awareness across soci­

ety about the value, challenges, and opportunities of conserving

and sustainably using marine resources. We work closely with

government bodies and civil society to inform public policies,

while also engaging directly with key social groups—including

women, traditional communities, and Indigenous peoples—to

foster collective transformation.

What did your oceanographic education (or academic

career) give you that is useful in your current job? 

My academic background was fundamental to my development

as a professional. I was fortunate to have a well-rounded under­

graduate education in oceanography that included not only

technical and scientific training but also courses in socioenvi­

ronmental topics. This broad foundation helped shape my sys­

tems thinking and gave me the ability to connect science with

society early on.

The technical knowledge I gained continues to be essential

in my work, especially in understanding marine ecosystems

and leading interdisciplinary teams. But just as important was

the development of critical thinking—a skill that allows me to

evaluate complex situations, design strategic interventions, and

adapt to ever-changing environmental and social realities.

Is there any course or other training you would have

liked to have had as part of your graduate education to

meet the demands of the job market? 

Yes—absolutely. To this day, I feel the absence of formal training

in areas like management, administration, and communication.

These skills are fundamental when working outside academia,

especially in leadership roles that require strategic planning,

team coordination, project oversight, and public engagement.

I also believe that basic training in entrepreneurship would be

extremely valuable for those interested in developing indepen­

dent initiatives or working across sectors. Incorporating even

introductory courses in these areas during graduate education

would better prepare scientists to operate in interdisciplinary

and applied contexts, where science meets society.

Is the job satisfying? What aspects of the job do you

like best/least? 

Yes, my job is deeply satisfying—but not without its challenges.

Like many people, I’m not fond of bureaucracy or the complex­

ities of managing human resources. Yet, paradoxically, those are

often the very things that challenge and push me to grow.

What I truly love is dreaming. I’m energized by imagining

how far good ideas can go, and by building the bridges to make

them happen. I enjoy thinking strategically—mapping visions

on paper and then adapting them as they come to life, often in

ways that differ from the original plan. Some ideas work, oth­

ers don’t, but when they do, and I see real-world impact, I feel

deeply fulfilled.

Do you have any recommendations for new grads

looking for jobs?

Follow your passion—even if it doesn’t seem “profitable” at first

glance. I’ve always been moved by nature and the ocean, and

although I was often told that this path lacked financial promise,

I never lost sight of what fulfilled me. Oceanography has always

been my passion, and being able to live it every day is a profound

source of personal and professional gratification.

I also believe deeply in the power of networks. The relation­

ships we build over time help sustain us and keep us connected

to shared causes. My advice is also to explore: seek out initiatives

that resonate with you, volunteer, get to know different fields,

and observe where your heart feels at home. And be proactive.

Having the courage to take initiative, choose your own path, and

take responsibility for your decisions is part of a rare and pow­

erful kind of growth—one that will shape both your career and

who you become along the way.

ARTICLE DOI. https://doi.org/10.5670/oceanog.2025.310

June 2025 | Oceanography

91

THE OCEANOGRAPHY SOCIETY’S

HONORS PROGRAM

One of the most meaningful aspects of being a member of

The Oceanography Society (TOS) is the opportunity to recog­

nize and celebrate our colleagues’ accomplishments. Please

take this opportunity to recognize a colleague, mentor, team,

or peer for their exceptional achievements and contributions

to the ocean sciences.

Medals

WALLACE S. BROECKER MEDAL is awarded biennially

to an individual for innovative and impactful contributions to

the advancement or application of marine geoscience, chem­

ical oceanography, or paleoceanography. Nomination dead­

line: October 31, 2025.

The NILS GUNNAR JERLOV MEDAL is awarded bien­

nially to an individual for advancing our knowledge of

how light interacts with the ocean. Nomination deadline:

October 31, 2025.

The WALTER MUNK MEDAL is awarded biennially to

an individual for extraordinary accomplishments and novel

insights contributing to the advancement or application of

physical oceanography, ocean acoustics, or marine geophys­

ics. Nomination deadline: October 31, 2025.

The MARY SEARS MEDAL is awarded biennially to an

individual for innovative, and impactful contributions to the

advancement or application of biological oceanography,

marine biology, or marine ecology, along with outstand­

ing contributions to education and mentorship in the field.

Nomination deadline: October 31, 2025.

Fellows

Recognizing TOS members who have made outstanding

and sustained contributions to the field of oceanography

through scientific excellence, extraordinary service and lead­

ership, and/or strategic development of the field. Nomination

deadline: October 31, 2025.

Awards

The TOS EARLY CAREER AWARD is presented bienni­

ally to up to three TOS Early Career members for significant

early-​career research contributions and impact, and the

potential for future achievements in the field of oceanogra­

phy. Nomination deadline: October 31, 2025.

The TOS MENTORING AWARD is given biennially to an

individual for excellence and/or innovation in mentoring the

next generation. Nomination deadline: October 31, 2025.

The TOS OCEAN OBSERVING TEAM AWARD is pre­

sented biennially to a team for innovation and excellence in

sustained ocean observing for scientific and practical appli­

cations. Nomination deadline: October 31, 2025.

tos.org/honors

Oceanography | Vol. 38, No. 2

92

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• Register by January 14, 2026 to take

advantage of early bird rates.

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available on a first-come, first-served basis.

• Abstract submission will open in

early July 2025.

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