Preliminary evidence of intra-offshore wind farm variation in epibiotic assemblages from automated ROV image analysis.

As global energy demand grows, our oceans are becoming increasingly industrialised. In the North Sea, one of the world's most developed marine regions, offshore infrastructure is shifting from isolated hydrocarbon platforms to large multi-turbine offshore wind farms (OWFs). These structures support diverse epibiotic assemblages which can influence structural integrity, alter ecological processes, and affect ecosystem service provisioning (e.g. water filtration). While epibiotic assemblage composition and zonation is well characterised on solitary structures, little is known about this varies at the intra-OWF scale. Our study explores this variation using ROV footage from a UK OWF; the foundations of two jacketed turbines situated at both the edge and centre of the OWF footprint were surveyed across all legs and depths, and the cover of five dominant epibenthic taxa quantified using a combination of structure-from-motion photogrammetry and machine-learning-based taxonomic segmentation. Epibiotic assemblages were dominated by anemones (Metridium senile) at intermediate depths, with increasing abundance of other target taxa at greater depths. While depth was the primary structuring factor, assemblage composition also appeared to vary with cardinal orientation and turbine position, with higher coverage of most target taxa at the OWF centre (notably soft corals (Alcyonium digitatum)). These patterns may be influenced by turbine-induced changes in downstream turbulence, stratification, and resource availability. While a limited sample size, our results suggest intra-OWF epibiotic heterogeneity, implying assemblage structure varies beyond depth zonation. As offshore wind development accelerates, research is needed to determine this variability's extent and drivers, helping to manage the consequences of an industrialised seascape.