265. Cable protection used to protect the export cable would also be colonised by the species and communities discussed above. In the worst case scenario up to 10% of the export cables to the east of the Greater Gabbard Offshore Wind Farm export cable crossing point and up to 2.5% of the export cable to the west of this point would be protected with rock armour, mattresses or sand-filled geotextile bags creating introduced hard substrate.
266. The change of habitat from a sandy sea bed to hard substrate would result in potential increases in the diversity and biomass of the marine community of the area through colonisation of the structures. However, there is likely to be only a small interaction between the remaining available sea bed and the introduced hard substrate and any interactions would be highly localised.
267. As previously discussed the species and habitats within the East Anglia THREE site and the offshore cable corridor are typical of those within the East Anglia Zone and wider southern North Sea. Given the localised nature of such habitat alteration, and the low value of the receptors the magnitude of the impact is considered to be low.
268. Sensitivity of the receptors is difficult to assess but due to their ubiquity in the region and the scale of these changes in relation to the communities present in the wider area, it is unlikely that the changes would result in any significant broad scale community or biodiversity changes. The sensitivity of the receptor is therefore considered to be at worst within the mediumcategory (Table 10.6).
269. When considering changes to existing communities the impact of colonisation of new substrate within the proposed East Anglia THREE project is likely result in a impact ofminor adverse significance. Confidence in the accuracy of this assessment is low and therefore a precautionary rating has been used when assigning the sensitivity of the impact.
270. The potential for colonisation of structures by non-native species, allowing them to extend their geographical range is also a possibility. Depending on the species, there is potential for secondary ecological changes to occur where there is competition between the non-native species and the native community.
271. Wilhelmsson and Malm (2008) noted examples of anthropogenic structures that constitute suitable habitats for non-indigenous species. Specifically, the study recorded that numerous specimens of the intertidal giant chironomid Telmatogeton japonicus, an Asian invasive species known to have been transported around the world in ship ballast and on ship hulls, were recently found in the splash zone on several of the wind turbines at Utgrunden on the Swedish Baltic coast and at other sites in Denmark. The species has also been recorded on offshore buoys in Belgium.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 1 Introduction Page 79
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