The Asian shore crab (Hemigrapsus sanguineus) and the brush-clawed shore crab (H. takanoi) both originate from east Asia but have in recent years established viable populations throughout coastal European waters. The two species are highly competitive and can occur in very high densities. Both species have been linked to the decrease of otherwise abundant native species such as the European shore crab (Carcinus maenas) and the common periwinkle (Littorina littorea). As both crabs are relatively new in European coastal waters, little is known about the full distribution range that may be achieved by these crabs and the ecological impact that may follow with an invasion of coastal habitats. In this study we investigated the potential distribution of Hemigrapsus in coastal waters of Northern Europe and the potential impact on the native competitor C. maenas. To this end we collected crabs on the Swedish west coast and on Helgoland and used these for behavioural experiments. We also collected new observation records of both species in Sweden and used these occurrences for building ecological niche models. We report that the potential distribution range of both H. sanguineus and H. takanoi extends from western Sweden to eastern Ireland (east-west) and southern Norway to western France (north-south). We also found evidence that H. takanoi can establish viable populations in nutrientrich inshore areas of the western and southern Baltic Sea and that competition by H. sanguineus is likely to affect abundances of C. maenas in the areas where these species co-occur.

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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).

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