June 2025

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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

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