Short-term effects of fishery exclusion in offshore wind farms on macrofaunal communities in the Belgian part of the North Sea

With the wide scale construction of offshore wind farms (OWFs) throughout the entire North Sea, large areas are permanently being closed to beam trawl fisheries. Beam trawling has affected macrobenthic assemblages for centuries, especially the fragile and long-lived species. Due to the prohibition of bean trawling in many OWFs, opportunities are being provided to investigate the potential recovery of vulnerable species and the creation of de-facto Marine Protected Areas (MPAs). The soft-substrate macrobenthic community was investigated from 2008 to 2012, before and after the construction of an OWF in the Belgian part of the North Sea, situated on the Bligh Bank. The fishery enclosed area (±21 km2) within the OWF (No Fishery area) was compared with a surrounding control area (±30 km2) where regular fishing activities were registered through vessel monitoring system (VMS) data throughout the period 2010-2011. Three years after the exclusion of beam trawl fisheries, subtle changes within the macrobenthic community were observed in the No Fishery area. The benthic mysid shrimp Gastrosaccus spinifer (30 ± 15 ind m−2), tube-building polychaetes Terebellidae sp. (196 ± 151 ind m−2) and the echinoderm Echinocyamus pusillus (73 ± 71 ind m−2), sensitive to trawling activities, showed increased abundances within the No Fishery area. With an expansion of the wind farm concession area to 238 km2 in the future, the likely increase of dense Terebellidae patches (e.g., Lanice conchilega reefs) within the No Fishery area could create an ecological important large-scale refugium for higher trophic levels. This study creates a baseline for the evaluation of long-term changes due to the fishing impacts and effects related to the presence of OWFs and highlights the importance of executing long-term monitoring programs in combination with targeted research.