Copepod by Russ Hopcroft, University of Alaska. Other plankton by Jay Nadeau, Chris Lindensmith, Jody W. Deming, Vicente I. Fernandez, and Roman Stocker. Image courtesy of David Liittschwager. - Extracted from this Commons file, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=106438820

At a Glance:

Despite being the smallest and most numerous of our marine species, the potential for offshore wind to impact plankton has not been overlooked. Because of their importance at the base of the marine food web, plankton have been the focus of hundreds of studies both before and after the placement of offshore wind turbine farms. Both positive and negative impacts have been observed in European waters. In general, impacts are regionally specific and much smaller in magnitude than the natural year-to-year and season-to-season variability of plankton productivity. Studies for new areas offshore of New England are planned, using both models to predict impacts and data collection for studies that will continue once the structures are in place.

A Deeper Dive:

A liter of seawater contains thousands of plankton cells of many different species. If you ever swallowed some seawater while swimming, you swallowed some plankton. You might wonder whether wind turbines could affect a resource so abundant as plankton. Scientists have seen alterations in the winds that stir the sea near turbines as well as changes in currents near the turbine platforms using direct measurement as well as mathematical models to estimate how widespread these effects will be. However, because plankton production is extremely variable in space (over meters to kilometers) and time (seasonally and from year to year) the impact of offshore wind is not easy to determine. Studies show that both incresaes and decreases are observed around wind turbines and that effects are likely to be localized. For example a recent study from the North Sea, using modelling to investigate impacts on plankton found that “the response in phytoplankton biomass is relatively small; on average below 1% both inside and outside the OWF clusters, but can reach up to 10% locally. An exception is the biomass change inside OWF clusters positioned in stratified areas, where the average response is about 2.4% but with large variations. Interestingly these locations also show a relatively strong increase in zooplankton biomass (12%)…” (Daewel et al. 2022 https://doi.org/10.1038/s43247-022-00625-0.

Scientists at NOAA and BOEM are committed to understanding offshore wind impacts on regions that are sensitive because of their important to commercial fisheries. Two examples of this commitment:

1) BOEM commissioned a study of the Massachusetts-Rhode Island marine areas where wind turbines are proposed in order to predict impacts on planktonic larvae of commercially important species including larvae of scallops, silver hake and summer flounder (Johnson et al. (2021) found that at the full proposed build out of turbines, the impacts were smaller than year to year changes that occur naturally. They concluded that at a “regional fisheries management level, these shifts in larval settlement density are not considered overly relevant” except possibly on certain subpopulations. They are continuing these studies.

2)BOEM also commissioned a study by the National Academy of Sciences, Potential Hydrodynamic Impacts of Offshore Wind Energy on Nantucket Shoals Regional Ecology: An Evaluation from Wind to Whales (2023). This report applied what is known from the North Sea models of hydrodynamics that are appropriate to the physical conditions of Nantucket Shoals, finding that “The hydrodynamic impacts from offshore wind development in the Nantucket Shoals region on zooplankton will be difficult to isolate from the much larger magnitude of variability introduced by natural and other anthropogenic sources (including climate change) in this dynamic and evolving oceanographic and ecological system.” Another important point to note is that the “The supply of zooplankton to Nantucket Shoals is dependent on regional circulation…”, in other words from plankton coming from areas far from where offshore wind turbines will be placed. Because some processes relating to the plankton, such as aggregations that might affect North Atlantic Right Whale feeding, are incompletely understood there is strong recommendation to directly observe the area both before and after the turbines are placed. As for the whales, whose behavior has been variable over time, impacts will only be understood after many years of study. “Because right whales forage over a vast geographic area, their use of any particular region may be partially driven by conditions in distant regions, such as alternative foraging habitats. It is plausible that zooplankton abundances in historical high-use foraging areas such as the Bay of Fundy and Roseway Basin will rebound, or right whales will increase occupancy in a different region (as recently done in the Gulf of St. Lawrence); thus, right whales may shift away from the Nantucket Shoals region to forage in these more northern areas.“