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,
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66 DIY OCEANOGRAPHY. The PIXIE: A Low-Cost, Open-Source, Multichannel
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86 BOOK REVIEW. A Philosophical View of the Ocean and Humanity, Second
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88 CAREER PROFILES. Lilian (Lica) Krug, Scientific Coordinator, Partnership
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66
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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
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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.
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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:
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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
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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
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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
17
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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TḥT MPA. Boundaries encompass all known hydrothermal vent fields
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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
FEATURE ARTICLE
HOW DO TIDES AFFECT
UNDERWATER ACOUSTIC PROPAGATION?
A COLLABORATIVE APPROACH TO IMPROVE INTERNAL WAVE MODELING
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.
June 2025 | Oceanography
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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
Oceanography | Vol. 38, No. 2
26
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)
June 2025 | Oceanography
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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.
June 2025 | Oceanography
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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.
Oceanography | Vol. 38, No. 2
30
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).
June 2025 | Oceanography
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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
Schönau, M.C., 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. 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
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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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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
59
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)
Oceanography | Vol. 38, No. 2
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
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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
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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
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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
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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.
June 2025 | Oceanography
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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advantage of early bird rates.
• Exclusive discounted hotel rates are
available on a first-come, first-served basis.
• Abstract submission will open in
early July 2025.
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