Assessment of the impact of offshore wind farm foundations in the English Channel on larval dispersal and connectivity using numerical modeling

Abstract

This work aims to investigate how the presence of Offshore Wind Farms (OWFs) could have local and potentially regional environmental impacts, as the turbine foundations serve as artificial habitats for various benthopelagic species, creating reef ecosystems. This study investigates how under met-oceanic forcings these farms could control the larval dispersion in the extended Bay of Seine. The dispersion of both natural species (mussel and European green crab) and introduced species (e.g. Japanese oyster and Asian shore crab) is simulated with coupled physical-biological numerical model combining MARS3D and ICHTHYOP. After a successful qualitative validation step using DILEMES data, it is observed that wind farms serve as relay points for species, facilitating connectivity between the farms and the shores of the extended Bay of Seine. Larval dispersal from the wind farms shows connectivity not only between the farms themselves but also between the farms and the shores of the extended Seine Bay, with approximately 7.44$\%$ of initially emitted larvae settling inside the Courseulles-sur-Mer OWF. As expected, the spatial resolution of the hydrodynamic model impacts the results, influencing larval retention particularly at the intersection of different nested grids. Our results indicate that it would be preferable to include effects of OWFs in future coastal management scenarios and underline the need to study cumulative impacts.