Inventory of the biofouling community on the first offshore solar energy farm in the North Sea

Abstract

Offshore renewable energy is rapidly expanding in the North Sea. Offshore solar is a new renewable energy technology currently developing in the Netherlands, with the first offshore tests of four years at rough conditions being successfully completed. Submerged parts of offshore renewable energy devices get fully colonised by fouling organisms, which take advantage of the new artificial habitats. In this study, we conducted an exploration of the fouling fauna that colonised the floaters of a solar farm installed for the first time in offshore waters in the Netherlands. The biofouling attached to the underwater parts of 18 floaters forming 3 clusters were sampled in a quantitative way by scuba divers. Macrofauna species and biomass were quantified in all samples. In total, 47 different taxa, including 12 non-indigenous species, were identified to occur on the floaters. Arthropoda (mainly individuals of the genus Jassa) was the most abundant phylum, while Mollusca (mainly blue mussel Mytilus edulis) showed the largest biomass. No significant differences in abundance nor biomass were observed between the two months of installation. Non-indigenous species were more abundant in number but contributed less to the total biomass compared to native species on the examined floaters, regardless of the month they were installed. The findings of this study suggest that, like any offshore artificial structure, offshore solar farms could act as stepping-stones for the spread of species. However, long-term monitoring is needed to confirm these results and gain a more comprehensive understanding of the development of fouling fauna on offshore solar farms.