Effects and Impacts of EMF Radiation from Undersea Cables on Marine Species
Written and prepared by Barbara K. Sullivan-Watts (April 2023)
Edited by Abbey Greene
Main Takeaways:
Marine animals may use their electromagnetic sense to navigate, detect prey or predators, communicate, or to mate.
Field and laboratory studies have provided reasonable confidence that the EMF levels emitted from marine renewable energy (MRE) cables are unlikely to cause significant risk to benthic or pelagic animals.
Evidence has shown that larger MRE arrays may increase the potential risk to sensitive marine receptors and require additional investigation, but no harm is likely to occur.
Cable protections such as burial that provide a physical barrier and reduce the maximum intensity that animals are exposed to does not eliminate the EMF.
Image Source: U.S. Bureau of Ocean Energy Management
Background information about EMFs and undersea cables:
Many marine animals detect electromagnetic fields (EMFs).
This ability has evolved multiple times across many species with a variety of sensory systems. This is not unexpected because EMFs pervade the whole of the earth’s environment and have been present throughout evolution of life on earth.
Why do marine species need this ability? Various marine species may have a magnetic compass or magnetic map that enables homing or migration over short and long distances. They also may use an electromagnetic sense to detect prey and predators, to communicate, and/or find mates.How does EMF from undersea cables work?
The placement of undersea cables that carry electricity is not new or unique to offshore wind. For example, there are already five undersea transmission lines connecting between Long Island and the Continental United States as of 2021 (Source: Wikipedia).
The transfer of electricity, either by direct current (DC) or alternating current (AC) cables, emits an EMF. Modern cable sheathing retains the electric field but the DC or AC magnetic field is emitted into the surrounding environment. EMF emitted varies with different electric currents (alternating (AC), or direct (DC)), cable length, distance from conductors, and energy output from the turbines. As an aside, heat is also emitted from these cables.
Potential impacts of EMF on marine species:
One recent synthesis of the science reports that field and laboratory studies have provided reasonable confidence that the EMF levels emitted from marine renewable energy (MRE) cables are unlikely to cause significant risk to benthic or pelagic animals. However, there are no standardized methods for measuring EMFs in the marine environment, or threshold levels against which to measure the emissions, particularly on a regulatory basis [52]. Evidence has shown that larger MRE arrays may increase the potential risk to sensitive marine receptors and require additional investigation, but no harm is likely to occur [52].
Authors of newer publications agree that reliable in-situ measurements of EMF emitted will have strength-dependent effects from none to measurable at the organism level, thus highlighting the need for reliable in-situ measurements. (In situ measurements are gathered by placing the measuring instruments directly at the point of interest and in contact with the subject itself.) This information is essential for policy making and for environmental assessments. (See Ref. Scott et al. (2021))
Another recent synthesis of the science highlights that the few in situ measurements that have been made indicate good agreement with models of DC magnetic fields, and that there are presently no thresholds indicating acceptable or unacceptable levels of EMF emissions in the marine environment (Hutchison et al. 2020). Cable protections such as burial that provide a physical barrier and reduce the maximum intensity that animals are exposed to does not eliminate the EMF, but it does minimize it.
Thermal radiation from cables is also discussed. Cables could be buried deeper but that prevents the heat from dissipating. Instead, heat builds up and could impact many organisms in the sediment. There are no specific regulations for thermal emissions from cables in the U.K.; however, German regulations require that the increase in temperature should not exceed 2 K (2 °C; Det Norske Veritas AS 2016)
John King, an Emeritus Professor of Oceanography at the University of Rhode Island, noted:
Speaking science: Marine biologists are concerned with “effects,’’ which are roughly defined as observable changes in behavior, or physiology at the individual or group level caused by an environmental variable, e.g. EMF. Marine biologists are also concerned with “impacts,” which are roughly defined as changes at the population level that can be attributed to the “effects.” Effects and impacts can be negative, neutral, or positive. The Bureau of Ocean Energy Management (BOEM), on the other hand, does not distinguish between effects and impacts in its regulatory framework. If effects are observed, then BOEM assumes that there is likely to be an associated impact. An effect is not necessarily predictive of an impact, so there is a bit of a disconnect between these two approaches from different perspectives.
Single cables vs. Cable Corridor: It is important to note that most in situ studies of effects on marine organisms are on single cables, and not on multiple cables. Some studies in Europe on the migration of eels seem to show that crossing multiple cables slows migration to the Sargasso Sea. Therefore while a single cable is likely not to be a barrier, either multiple cables along a migration route, or multiple cables in a cable corridor might become a barrier. Scientists are not sure yet. King imagined that a possible impact on the American eel could be imagined if the farms act as a barrier to their regular speed of migration to the Sargasso Sea from their freshwater habitats.
DC vs. AC: King also mentioned that on the issue of Direct Current (DC) versus Alternating Current (AC) – “It is not correct science to say that AC has no effect yet, whereas it is correct that organisms show less of a reaction to AC fields than DC fields. New research on how marine organisms detect and react to AC fields is in progress. For now, it is safe to say that AC is better than DC and that cables that reach project burial depths are better than those that don’t.”
Key Quotes from the Syntheses of Science:
“Present understanding of the interactions between EMFs and marine animals has benefited from laboratory experiments and field studies using surrogate cables, largely with benthic fish and invertebrates [49,50,51]. However, significant gaps remain in understanding how pelagic species (e.g., sharks, marine mammals, fish) may react to dynamic cables suspended in the water column [52].”
“The levels of EMF reported in many field and laboratory studies are much higher than those expected from MRE export cables [53] and the evidence to date suggests that the levels are unlikely to keep animals away from their preferred habitats or affect migration patterns [54,55].”
“There is a need, however, to better understand the likely EMF emissions from MRE cables, based on the configuration and electricity loads of specific cables, to identify potential effects, particularly as the MRE industry scales up to large-scale arrays [52].”
“Although burial of cables and other measures such as placement of concrete mattresses are not considered to be effective ways to mitigate magnetic emissions into the marine environment, burial separates most sensitive species from the source of the emissions [56].”
Learn Even More:
Potential Environmental Effects of Marine Renewable Energy Development—The State of the Science from the Coastal Sciences Division in the Pacific Northwest National Laboratory
Fisheries and Offshore Wind Interactions: Synthesis of Science from the NMFS (National Marine Fisheries Service) and the NEFSC (Northeast Fisheries Science Center)
References:
49 Hutchison, Z.; Sigray, P.; He, H.; Gill, A.; King, J.; Gibson, C. Electromagnetic Field (EMF) Impacts on Elasmobranch (shark, rays, and skates) and American Lobster Movement and Migration from Direct Current Cables; Bureau of Ocean Energy Management, U.S. Department of Interior: Sterling, VA, USA, 2018.
50 Hutchison, Z.; Gill, A.; Sigray, P.; He, H.; King, J. Anthropogenic electromagnetic fields (EMF) influence the behaviour of bottom-dwelling marine species. Sci. Rep. 2020, 10, 4219. [Google Scholar] [CrossRef][Green Version]
51 Siegenthaler, A.; Niemantsverdriet, P.; Laterveer, M.; Heitkönig, I. Aversive responses of captive sandbar sharks Carcharhinus plumbeus to strong magnetic fields. J. Fish Biol. 2016, 89, 1603–1611. [Google Scholar] [CrossRef]
52 Gill, A.; Desender, M. Risk to Animals from Electro-magnetic Fields Emitted by Electric Cables and Marine Renewable Energy Devices. In OES-Environmental 2020 State of the Science Report: Environmental Effects of Marine Renewable Energy Development around the World; Copping, A.E., Hemery, L.G., Eds.; Ocean Energy Systems (OES): Lisbon, Portugal, 2020; pp. 86–103. [Google Scholar]
53 Normandeau Associates Inc.; Exponent Inc.; Tricas, T.; Gill, A. Effects of EMFs from Undersea Power Cables on Elasmobranchs and other Marine Species (OCS Study BOEMRE 2011-09); Bureau of Ocean Energy Management Pacific OCS Region, U.S. Department of the Interior: Camarillo, CA, USA, 2011.
54 Anderson, J.; Clegg, T.; Véras, L.; Holland, K. Insight into shark magnetic field perception from empirical observations. Sci. Rep. 2017, 7, 11042. [Google Scholar] [CrossRef] [PubMed][Green Version]
55 Wyman, M.; Klimley, A.; Battleson, R.; Agosta, T.; Chapman, E.; Haverkamp, P.; Pagel, M.; Kavet, R. Behavioral responses by migrating juvenile salmonids to a subsea high-voltage DC power cable. Mar. Biol. 2018, 165, 134. [Google Scholar] [CrossRef]
56 Copping, A.; Sather, N.; Hanna, L.; Whiting, J.; Zydlewski, G.; Staines, G.; Gill, A.; Hutchison, I.; O’Hagan, A.; Simas, T.; et al. Annex IV 2016 State of the Science Report: Environmental Effects of Marine Renewable Energy Development Around the World; Ocean Energy Systems (OES): Lisbon, Portugal, 2016. [Google Scholar]
Ref Scott et al. Kevin Scott, Petra Harsanyi , Blair A. A. Easton, Althea J. R. Piper, Corentine M. V. Rochas
1 and Alastair R. Lyndon Exposure to Electromagnetic Fields (EMF) from Submarine Power Cables Can Trigger Strength-Dependent Behavioural and Physiological Responses in Edible Crab, Cancer pagurus (L.)
J. Mar. Sci. Eng. 2021, 9(7), 776; https://doi.org/10.3390/jmse9070776