This document reviews available information relating to barrier effects, entanglement risks from ghost fishing gear, and ElectroMagentic Fields (EMFs) with regards to marine mammals, diving seabirds, fish, and invertebrates at Floating Offshore Windfarms (FOW). To do this, available information from comparable offshore industries including fixed windfarms, Oil & Gas, aquaculture, etc., is explored, and knowledge gaps identified to steer research efforts in future.
There are currently no first-hand accounts of barrier effects being caused by operational FOWs on marine fauna. Studies from parallel industries indicate that, for odontcoetes (toothed whales, dolphins, and porpoises) and pinnipeds (seals, sea lions, and walruses), physical presence of FOWs is unlikely to cause a barrier effect, and if anything, animals may be attracted to FOWs for foraging. Due to a lack of evidence for how mysticetes (baleen whales) interact with anthropogenic structures, there is potential for a behavioural response to physical structures at a FOW. Similarly, diving seabirds, turtles, fish, and elasmobranchs (sharks, skates, and rays) are not considered to be at risk of barrier effects from FOWs. Further evidence is needed regarding marine fauna's usage of operational FOW sites and how they pass through and between moorings and cables. There is potential for impacts to arise as size of FOWs increases in future, which may be of particular concern for migratory species such as mysticetes.
Direct entanglement with FOW structures is unlikely for marine species due to the size and tension of subsea cables and moorings; however, secondary entanglement, when individuals become trapped in other ropes or derelict fishing gear which is snagged on moorings and cables, presents a higher risk. This is a risk for a variety of taxa from marine mammals, to diving seabirds, turtles, fish, and invertebrates. Direct effects of entanglement include mortality or serious injury; however, individuals that break free from entanglement may suffer respiratory distress or damage to tissues, muscles, or nervous systems. There is a significant knowledge gap on rates of ghost fishing gear snagging on FOW cables and moorings and subsequent rates of animal entanglement.
Electric and magnetic fields produced by subsea cables present a potential stressor to nearby animals. Strength of fields declines with distance from the source. Effects of EMFs on marine species are generally understudied and not well known. Certain taxa, such as sharks, which are known to be receptive to EMF, are likely more impacted by electromagnetic fields produced by subsea cables than species less reliant on detecting EMFs for foraging and navigation.
In summary, impacts of barrier effects and EMF are likely to be minimal for most species. Risk of injury or mortality from entanglement in ghost fishing gear is high for individuals that become entangled; however, given a lack of information on rate of gear snagging on FOW structures and consequently rate of animal entanglement at FOW sites, it is not known if this will pose a significant risk for populations.