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).
Highlights
The effects on local benthic habitats during installation works and operations of Offshore Wind Farms (OWF) are of a complex nature and extend both below and above the surface of the sea
1.1 Aim The aim of this study was to 1) Ascertain whether or not similar impacts, with regards to colonisation on turbines and associated structures, to those observed at traditional OWFs were present at the Hywind Scotland Pilot Park, and 2) Assess if any zonation patterns were present on the Hywind Scotland Pilot Parks structures, similar to those observed at traditional OWFs. 3) To 50 quantify diversity, abundances and 4): identify if any non-indigenous species were present
To confirm the presence or absence of invasive and non-indigenous species on 260 the structures, physical samples are recommended for future surveys as a complement to the visual inspection
Summary
The effects on local benthic habitats during installation works and operations of Offshore Wind Farms (OWF) are of a complex nature and extend both below and above the surface of the sea. Previous studies have shown that OWFs can impact areas through the introduction and spread of alien species (Wilhelmsson and Malm, 2008; Vattenfall, 2006), affect sediment composition (Degraer et al, 2019) and alter community structures (Degraer et al, 2019; Vattenfall, 2006; Wilhelmsson and 30 Malm, 2008) through the loss of soft sediment habitats and the subsequent introduction of artificial hard bottom substrates. 35 Studies conducted at OWFs around the North Sea show that the faunal and floral communities on turbines can further be categorised into distinct zones from the splash zone to the intertidal and deep subtidal zone A FOWF, not subject to these 45 restrictions, opens up new possibilities with regard to installation locations
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