Long-term impacts of offshore wind farms presence on benthic communities in the Belgian part of the North Sea

This study investigates the long-term impacts of offshore wind farms (OWFs) on macrobenthic communities at a far distance (250-500 m) from wind turbines in the C-Power offshore wind farm, on the ThorntonBank (Belgian Part of the North Sea) over a time span of 15 years (2005- 2020). We anticipated that due to the changes in hydrodynamics around wind turbines, together with the increase in depositional flow of faecal pellets produced by filter-feeding epifauna living on the foundation of the wind turbine, there will be an increase in macrobenthic abundance and species richness, as well as a shift in macrobenthos community composition. We also hypothesized that owing to fishery exclusion in offshore wind farms concession areas the ThorntonBank (impact area) and GooteBank (reference area) would grow apart from each other in terms of abundance and species richness, as well as in terms of species composition. Our 15 years analysis supported the hypothesis of an increase in macrobenthic abundance and species richness as fine sediment fraction and total organic matter content increase within the sediment of OWFs. The appearance and subsequent increase in Terebellidae sp. and Ophelia borealis suggested a shift in macrobenthos community composition when compared to the baseline study of 2005. However, changes in macrobenthic abundance, species richness and species composition were observed on both sandbanks, suggesting that either human activities that once took place on the GooteBank affected the communities there, or adding wind turbine does not generate strong impacts on macrobenthic communities. The observed fluctuations over the years could then be due to normal fluctuations in macrobenthos, or that other factors are at play such as climate change. However, in order to confirm these statements, additional studies on macrobenthos within the Belgian Part of the North Sea should be done on the long term. Further analysis should also be carried out in order to confirm the potential shift from a Nepthys cirrosa community toward an Abra alba community

RBINS Publication(s), Master thesis

Keywords: macrobenthos, Belgian Part of the North Sea (BPNS), offshore wind farms, long- term study, renewable energy, environmental impact.