Long-term impact of turbine presence on macrobenthic communities in the Belgian Part of the North Sea

The present study examines the long-term effects of offshore wind farms (OWF) on macrobenthic communities in two OWFs, Belwind and C-Power, located in the Belgian Part of the North Sea (BPNS) over a 13-year period. We hypothesized that not only turbine presence, but also climate change and natural fluctuations in Sea Surface Temperature (SST) would affect macrobenthic communities in the long term. The findings support existing knowledge of turbine-related effects. Macrobenthos diversity, abundance and species richness increase with finer sediment fractions, organic matter, and in gullies between sandbanks. On top, impacts differed between locations, illustrating that they can be site-specific depending on local conditions. Climate-related factors such as SST and Atlantic Multidecadal Oscillation were significantly incorporated in the models predicting macrobenthic diversity and composition, however, no clear patterns emerged. Consequently, climate variables do not replace the influence of local environmental factors impacted by turbine presence and water depth in our study, but have to be taken into account when studying long-term trends. Our analysis further revealed the absence of a stable state after 13 years of OWFs' presence in the BPNS, emphasizing that long-term studies are essential for understanding the natural variability of macrobenthic communities on top of anthropogenic factors.