73.
The potential impacts of the proposed East Anglia THREE project are all associated with the operational phase.
9.11.1 Invertebrates 74. Despite many marine invertebrates being magnetically sensitive, evidence of interactions with anthropogenic sources of magnetic fields is limited and often contradictory. The brown shrimp (Crangon crangon) has been recorded as being attracted to AC B fields of the magnitude expected around windfarms (ICES 2003). Shore crabs (Carcinus maenas) have been demonstrated to be less aggressive in the presence of an AC B field generated to match the magnitude of windfarm cabling (Everitt 2008). Contrastingly, Bochert & Zettler (2004) found no effects of exposure to static B fields upon the same species, or upon the round crab (Rhithropanopeus harrisii), an isopod (Saduria entomon) or the mussel (Mytilus edulis).
75.
The deeper the cables are buried, the weaker the B field encountered by most marine fauna would be (except burrowing species such as polychaetes and bivalve molluscs). However, where cables are covered by cable protection, invertebrates are likely to colonise interstitial spaces and may therefore come into direct contact with the cables and potentially be exposed to stronger fields.
76.
The potential for effects of B fields from East Anglia ONE on invertebrate navigation or physiological effects may exist within tens of metres of separated HVDC cables and within close proximity of bundled HVDC and HVAC cables. However, physiological effects are expected to be largely negated through burial.
77. No marine invertebrates have been definitively demonstrated as being electrically sensitive. The iE fields expected to be induced by the proposed East Anglia THREE project are of relatively minimal strength and therefore no effects are expected upon marine invertebrates.
9.11.2 Fish 78.
Available research suggests that magnetic fields from cables have little ecological effect. Bochert & Zettler (2004) found no significant effects of static B fields upon flounder, Platichthys flesus. Swedpower (2003) found no measurable impact of subjecting salmon and trout to magnetic fields twice the magnitude of the geomagnetic field. In line with this, Atlantic salmon migration in and out of the Baltic Sea, over a number of operating sub-sea HVDC cables, seems to continue unaffected (Walker 2001). The European eel has been shown to deviate from its migration route in the presence of a 5µT HVDC field, however the effect was short term and over a short distance (Westerberg 2000; Ohman et al. 2007), and such
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 9 Underwater Noise Page 18
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