to the establishment of new faunal communities and new species. Clear biological zones were evident with mussels dominating the foundations between 7 and 10m deep while below 10m depth foundations were colonised by tubes of the small crustacean Jassa sp. and anemones (Metridium senile, Sargartia spp. and Diadumene cincta). During surveys, 33 species were found to have colonised the monopiles and 17 species on the scour protection after two years of monitoring (Lindeboom et al. 2011).
260. Studies in the UK have identified increases of benthic species including crabs (C. pagurus) and lobsters (H. gammarus) from colonisation of sub-surface structures by subtidal sessile species (Linley et al. 2007) on which they can feed.
261. Monitoring at Horns Rev 1 OffshoreWindfarm in Danish waters showed that the sub-surface structures were colonised by 11 species of algae and 65 invertebrate taxa within two years of the completion. In addition, mobile invertebrates (decapods and molluscs) were found on the scour protection and sessile species had settled on the monopiles.
262. Monitoring at the Alpha Ventus windfarm in German waters found that the mussel Mytilus edulis contributed the largest part of the biomass (75%) on the upper 5m of wind turbine foundations whilst deeper areas of foundations were dominated by the amphiopod Jassa sp (ICES 2012).
263. It has been suggested by consultees of other windfarms that the introduced hard substrate could act as ‘stepping stones’ for colonisation by non-native species into UK coastal waters. However, it is not possible to assign a clear impact to this potential issue. In 2009, Cefas conducted a review of the state of the benthic ecology around Round One windfarms (Cefas 2009), in this review no invasive or non-native species were observed although monitoring was recommended throughout the life span of all windfarms.
264. Gravity base structures and associated scour protection are likely to represent the worst case scenario as they have the greatest footprint and therefore the most potential for changing the biodiversity. Lindeboom et al. (2011) found that new hard substrate introduced by the construction of the Egmond aan Zee Offshore Windfarm acts as a new type of habitat with a higher biodiversity of benthic organisms and indicated a possible increased use of the area by the benthos, fish, marine mammals and some bird species. Neither the surrounding soft sediment benthic community nor bivalve recruitment was found to be affected by the windfarm during the first year of operation.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 1 Introduction Page 78
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