Abstract. Artificial substrates associated with renewable offshore energy infrastructure, such as floating offshore wind farms, enable the establishment of benthic communities with a taxonomic composition similar to that of naturally occurring rocky intertidal habitats. The size of the biodiversity impact and the structural changes in benthic habitats will depend on the selected locations. The aim of the study is to assess colonisation and zonation, quantify diversity and abundance, and identify any non-indigenous species present within the wind farm area, as well as to describe changes in the epifouling growth between 2018 and 2020, with regards to coverage and thickness. This article is based on work undertaken within the offshore floating Hywind Scotland Pilot Park, the first floating offshore wind park established in the world, located approximately 25 km east of Peterhead, Scotland. The floating pilot park is situated in water depths of approximately 120 m, with a seabed characterised predominantly by sand and gravel substrates with occasional patches of mixed sediments. The study utilised a work class remotely operated vehicle with a mounted high-definition video camera, deployed from the survey vessel M/V Stril Explorer. A total of 41 structures, as well as their associated sub-components, including turbines substructures, mooring lines, suction anchors and infield cables, were analysed with regards to diversity, abundance, colonisation, coverage and zonation. This approach provides comprehensive coverage of whole structures in a safe and time-saving manner. A total of 11 phyla with 121 different taxa were observed, with macrofauna as well as macroalgae and filamentous algae being identified on the different structures. The submerged turbines measured approximately 80 m in height and exhibited distinct patterns of zonation. Plumose anemones (Metridium senile) and tube-building fan worms (Spirobranchus sp.) dominated the bottom and mid-sections (80–20 m) of the turbines, while kelp and other Phaeophyceae with blue mussels (Mytilus spp.) dominated top sections of the turbines (20–0 m). A general increase in the coverage of the epifouling growth between 2018 and 2020 was observed, whereas the change in thickness between years was more variable.

Abstract. Artificial substrates associated with renewable offshore energy infrastructure, such as Floating Offshore Windfarms, enables the establishment of benthic communities with similar diversity species composition to that of naturally occurring rocky intertidal habitats. The size of the biodiversity impact and the structural changes on benthic habitats will depend on the selected locations. The aim of the study was to assess colonisation, zonation, quantify diversity and abundance, and identify any non-indigenous species of fauna and flora present within the wind farm. This article is based on work undertaken within the offshore floating Hywind Scotland Pilot Park, the first floating offshore wind park established in the world, located approximately 25 km east of Peterhead, Scotland. The floating pilot park is situated in water depths of approximately 120 m with a seabed characterised predominantly by sand and gravel substrates with occasional patches of mixed sediments. The study utilised a Work Class Remotely Operated Vehicle with a mounted High Definition video camera, deployed from the survey vessel M/V Stril Explorer. A total of 41 structures, as well as their associated subcomponents, including Turbines (Substructures), Mooring Lines, Suction Anchors and Infield Cables, were analysed with regards to diversity, abundance, colonisation, coverage and zonation. This approach provides comprehensive coverage of whole structures in a safe and time-saving manner. Eleven phyla were observed with a total of 121 different taxa, macrofauna as well as macro- and filamentous algae, identified on the different structures. The submerged turbines measured approximately 80 m in height and exhibited distinct patterns of zonation. Plumose anemone Metridium senile and tube building fan worm Spirobranchus sp. dominated the bottom and mid-sections (80 m–20 m) of the turbines while kelp and other Phaeophyceae with blue mussel Mytilus spp. dominated top sections of the turbines (20 m–0 m).

In this study, we collected water eDNA from sampling stations at the first full scale floating offshore wind farm (OWF), the Hywind Pilot Park, east of Peterhead, UK, and a nearby reference area. We combined targeted droplet digital PCR (ddPCR) quantification of two commercially important species, Atlantic mackerel (Scombrus scombrus) and Atlantic herring (Clupea harengus), with metabarcoding of fish and plankton communities. The goal of this study was to assess the performance of eDNA data to characterize pelagic communities and its use for environmental monitoring. The metabarcoding recovered 26 fish species including both pelagic and demersal taxa. The plankton data were dominated by dinoflagellates (Karenia) and calanoid copepods. We found that both specific quantification of eDNA from mackerel and herring and eDNA metabarcoding of fish communities were able to reveal spatial patterns: Mackerel was most abundant in the surface across both OWF and reference sites; herring was present at a wider depth range. While ddPCR and metabarcoding data for these two species were broadly congruent, we observed detection/non‐detection mismatches for both methods, highlighting the need for robust sampling design. There was no consistent OWF versus reference area pattern in the demersal fraction of fish assemblages. We interpret our findings as representing a snapshot of fish school location around the time of sampling, and do not consider the single timepoint data from this pilot study to be sufficient to attribute any effects to the OWF itself. As a non‐invasive tool, we conclude that eDNA has a high potential in future environmental monitoring of OWFs. We recommend further ground‐truthing and biomass correlation of eDNA data with catch data and establishing eDNA time series as next steps towards implementation of eDNA in OWF environmental monitoring.