East Anglia ONE Executive Summary
The following report relates information from research and literature review on expected electromagnetic fields (EMF) from sub-sea cabling associated with the planned East Anglia One Offshore Wind Farm with current understanding of the potential effects of such EMF upon marine organisms.
There are a number of cabling designs being considered, including both alternating current (AC) and direct current (DC) cables of different voltage ratings. Alternating current cables are most likely to consist of three-core technology, although there is a small possibility that single-core cables might be used (likely deployed in trefoil but possibly separately). Direct current cables will be bipole systems, whereby current is transmitted along two separate cables in opposite directions, with bundling of the two cables the most likely deployment method, although there is a small possibility that they may be separated. Tentative predictions of estimated EMF expected to be generated by each cable design and deployment are included.
The current flowing through the cables generates a magnetic (B) field, which constantly changes with AC cabling, but is static with DC cables. B fields are expected to attenuate rapidly with distance from cables. Bundling single-core AC and bipole DC cables reduces B field generation owing to cancellation effects of similar fields transmitted along adjacent cables in opposite directions. Electric fields generated by the cables directly will be shielded and not emitted to the environment. However, electric fields may be induced (iE fields) by the movement of B fields generated by AC cabling through seawater, and by tidal flow or marine fauna moving through the B field generated by DC cabling. Owing to their dependence on B fields, these iE fields are also expected to attenuate rapidly with distance from the cables.
Review of the literature reveals a large number and wide variety of organisms that are sensitive to electromagnetic fields (EMF). The main concerns relating to B field emanation are potential impairment of navigation and physiological effects. The main concerns relating to iE field emanation are potential repulsion, confusion with bioelectric fields and physiological effects. Research into electromagnetically sensitive species and their interactions with anthropogenic EMF is ongoing and at an early stage, but cautious assessment of potential effects of EAONE EMF upon marine fauna has been undertaken.
No effects are expected for either B or iE fields upon marine flora or micro fauna, nor marine mammals and chelonians. Marine invertebrates are expected to be unaffected by iE fields, but may potentially be affected by B fields (navigation and/or physiology). Teleost fish may potentially be affected by both B (navigation and/or physiology) and iE fields (navigation). Elasmobranchs are highlighted as potentially the most vulnerable taxa, owing to their acute sensitivity to EMF and their use of electro-sense for prey detection, predator avoidance, mate location, in addition to orientation and migration. B fields have potential to affect their navigation, while iE fields have potential to cause confusion (weaker fields) or avoidance (stronger fields). Most effects are, however, expected to be minor and temporary, occurring only within close proximity of the cables.
EMF Assessment
J3184 EAONE v2
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