Abstract
In offshore wind farms (OWF), subsea power cables carry electricity within (inter-array cables) and from OWF to land (export cables). These cables generate electromagnetic fields (EMF), both electric (E‐fields, measured in Volts/m) and magnetic (B‐fields, measured in Tesla), that potentially can affect marine organisms raising environmental concern. E-fields may affect certain marine species that are electroreceptive, such as some types of sharks and rays, that have specialized electroreceptive organs (ampullae of Lorenzini). These organs are sensitive to weak electric fields produced by prey, and e-fields can potentially affect the ability to locate prey in electrosensitive animals. B-fields are more likely to have effects on marine species that rely on geomagnetic cues and navigation, thus potentially disrupting natural behaviour and navigation patterns. Even though geomagnetic reception has been observed in a wide range of taxa, from bacteria to whales, the biological mechanisms underlying geomagnetic reception is largely unknown.
The impact of EMF on marine organisms largely depends on the strength of the fields, the proximity of the cables to sensitive habitats, and the sensitivity of the species present in the area. Cable insulation may reduce E-fields, and cable burial may reduce the environmental impact of both E-fields and B-fields. The strength of EMFs varies depending on the voltage and current carried by the cables. High-voltage direct current (HVDC) export cables tend to produce stronger EMFs, primarily B-fields, compared to alternating current (AC) cables. HVDC cables, which are responsible for transmitting the collected electricity from a central offshore substation to the onshore electrical grid, are of a high voltage and capacity, run over longer distances, and are typically buried in the seabed. Thus, benthic and epi-benthic communities in the surrounding area will be subjected to B-fields. Many marine invertebrates inhabit these communities and play crucial roles in the ecosystem. These species are often sessile and are therefore likely to experience high and long-term exposure to cable-generated EMF. Some benthic invertebrates are known to be electro- and magneto-sensitive. Behavioural responses to EMF have, however, been observed in some invertebrate species. Behavioural changes can lead to alterations in the interactions and dynamics of populations, potentially resulting in reduced survival, growth and reproduction for susceptible species. EMF may therefore potentially cause changes to biodiversity, but this has been poorly studied.
SINTEF Ocean has developed an experimental system enabling exposure of marine organisms to EMF in a controlled manner. The system consists of an exposure arena, where small marine organisms, such as crustaceans, echinoderms and fish larvae, can be filmed and monitored for behaviour for long periods of time while being subjected to a down-scaled version of realistic magnetic fields from submarine cables. The primary focus of research associated with this system is to assess the behavioural effects of EMF on a range of marine species, with the goal of establishing effect thresholds for EMF. This will contribute to evaluating the potential for EMF to be an environmental risk driver for offshore wind installations.
The impact of EMF on marine organisms largely depends on the strength of the fields, the proximity of the cables to sensitive habitats, and the sensitivity of the species present in the area. Cable insulation may reduce E-fields, and cable burial may reduce the environmental impact of both E-fields and B-fields. The strength of EMFs varies depending on the voltage and current carried by the cables. High-voltage direct current (HVDC) export cables tend to produce stronger EMFs, primarily B-fields, compared to alternating current (AC) cables. HVDC cables, which are responsible for transmitting the collected electricity from a central offshore substation to the onshore electrical grid, are of a high voltage and capacity, run over longer distances, and are typically buried in the seabed. Thus, benthic and epi-benthic communities in the surrounding area will be subjected to B-fields. Many marine invertebrates inhabit these communities and play crucial roles in the ecosystem. These species are often sessile and are therefore likely to experience high and long-term exposure to cable-generated EMF. Some benthic invertebrates are known to be electro- and magneto-sensitive. Behavioural responses to EMF have, however, been observed in some invertebrate species. Behavioural changes can lead to alterations in the interactions and dynamics of populations, potentially resulting in reduced survival, growth and reproduction for susceptible species. EMF may therefore potentially cause changes to biodiversity, but this has been poorly studied.
SINTEF Ocean has developed an experimental system enabling exposure of marine organisms to EMF in a controlled manner. The system consists of an exposure arena, where small marine organisms, such as crustaceans, echinoderms and fish larvae, can be filmed and monitored for behaviour for long periods of time while being subjected to a down-scaled version of realistic magnetic fields from submarine cables. The primary focus of research associated with this system is to assess the behavioural effects of EMF on a range of marine species, with the goal of establishing effect thresholds for EMF. This will contribute to evaluating the potential for EMF to be an environmental risk driver for offshore wind installations.