A recent article in Current Biology entitled Marine mammals trace anthropogenic structures at sea highlights how marine mammals may interact with offshore windfarms. As new larger scale installations become more common, research of this kind will support observations of in situ array-scale impacts of windfarms. A team of scientists, headed by Deborah Russell of the Sea Mammal Research Unit (SMRU), tracked tagged harbor seals and grey seals near two wind farms in the North Sea: Sheringham Shoal, with 88 3.6 MW turbines, is located in the south-east United Kingdom; and Alpha Ventus, with 12 5 MW turbines, is located off the shores of Germany. The results were conclusive: the seals are using the wind farm structures to forage. In addition to showing foraging behavior near the wind turbine towers, about half of the seals moved in a grid pattern through the windfarm, efficiently navigating between structures.
Over 100 seals were tagged in this experiment, and 11 were recorded entering the windfarms while the wind turbine was operational; most of these 11 seals made multiple trips through the windfarms. Looking at a separate set of tagged seals, similar patterns were recorded, showing seals traveling and foraging along pipelines. Male and female, adult and juvenile seals all foraged among the wind turbines and along the pipelines. At the time of the study, the wind farms had been recently installed. Over time, aggregation of the seals around the wind farms might even increase. One could speculate that further increases of anthropogenic structures in the water, such as marine renewable energy devices, might further increase foraging by seals.
Researchers at SMRU and their colleagues attempted to explain the seals’ behavior but could not discern whether prey organisms were concentrated around the structures, drawing the seals close, or whether an overall increase in prey in the North Sea was supporting more seals. Unraveling this mystery could lead to further understanding of the larger scale environmental consequences of windfarm installations.
SMRU’s paper has attracted attention from many news outlets, indicating intense public interest in the subject of offshore wind environmental effects. Many of the mainstream media articles sensationalized the results, with titles exclaiming “Seals Thrive Around Wind Farms” or asking “Why do seals love offshore wind farms?”.