Marine animals

Some marine animals such as sharks and fish can perceive weak fields such as the Earth’s magnetic field with special sensory organs and orientate themselves accordingly. These animals can also sense the fields emitted by power cables and change their behaviour accordingly. Some cartilaginous fish (including sharks, rays, and manatees) tend to search for prey near the submarine cables ^[1] as long as the fields are weak. Within a few days, sharks learn to associate electric fields with the presence of prey; they also learn to ignore fields from power cables where no prey is found ^[2]. This indicates that they can adapt well to the changed conditions and that their hunting success is not affected by the fields emitted by cables

Some fish species (e.g. salmon and eels) orient themselves to magnetic fields during their migrations. These animals perceive the magnetic field of the submarine cables, swim more slowly in the immediate vicinity of the cables, and change their swimming direction over a short section of their journey ^[3]. However, according to previous study findings, they appear to be only slightly deflected in their direction of migration. The cables do not have a complete barrier effect.

Observational studies of coral reef fish in Florida have shown that emissions from submarine cables have no effect on the biodiversity of fish populations there ^[4].

The effects of magnetic fields on invertebrates, especially crustaceans and molluscs, are summarised in a review paper ^[5]. Only a few species were examined as examples. Long-term exposure to magnetic fields has no predominant effect on survival, reproduction or physiological parameters in several species of crustaceans and molluscs. Many crustaceans perceive magnetic fields and orient themselves accordingly. About half of the species studied prefer areas with elevated magnetic fields (e.g. the edible crab (Cancer pagurus)) or increase their activity in the presence of these fields (e.g. the American lobster (Homarus americanus)). The fields do have a minor physiological effect on the daily rhythm of the animals but are not harmful. In contrast, other species show no behavioural response to magnetic fields (e.g. young European lobsters (Homarus gammarus)) but a few avoid them (e.g. spiny lobsters (Palinuridae)).

Serious harmful effects (e.g. genetic damage or tissue damage in marine life) are not expected because the strength of the electric and magnetic fields is low. The behavioural changes described can lead to the redistribution of individual species. The number of offshore wind turbines and the submarine cables required for them is constantly increasing. Isolated encounters with cables do not pose a risk to marine animals. However, if the hunting behaviour, migration, or movement activity of certain species is disturbed too often, this can lead to energy losses. This, in turn, could have an effect on populations and ecosystems. The current state of scientific knowledge on the environmental effects of extracting renewable energy from the sea is summarised in a review paper, which also contains outlooks for the future and research recommendations ^[6].

[1] Hutchison ZL, Gill AB, Sigray P, He H, King JW. (2020) Anthropogenic electromagnetic fields (EMF) influence the behaviour of bottom-dwelling marine species. Sci. Rep. 10:4219.

[2] Kimber JA, Sims DW, Bellamy PH, Gill AB. (2014) Elasmobranch cognitive ability: Using electroreceptive foraging behaviour to demonstrate learning, habituation and memory in a benthic shark. Anim Cogn 17:55-65.

[3] Westerberg H, Lagenfelt I. (2008) Sub-sea power cables and the migration behaviour of the european eel. Fisheries Manag Ecol 15:369-375.

[4]Kilfoyle AK, Jermain RF, Dhanak MR, Huston JP, Spieler RE (2018) Effects of emf emissions from undersea electric cables on coral reef fish. Bioelectromagnetics 39(1): 35-52.

[5]Albert L, Deschamps F, Jolivet A, Olivier F, Chauvaud L, Chauvaud S (2020) A current synthesis on the effects of electric and magnetic fields emitted by submarine power cables on invertebrates. Mar Environ Res 159: 104958.

[6]Gill A, Desender M. State of the science report, Chapter 5: Risk to animals from electromagnetic fields emitted by electric cables and marine renewable energy devices. United States: Pacific Northwest National Lab; 2020:87-103.