Publication of the SPECIES project report on the potential impact of MRE project power cables on coastal benthic ecosystems

Environmental issues

The first commercial offshore wind farms will soon be established in France and significant focus is placed on their potential environmental impact. Amongst the concerns of the both the general public and scientists, and regularly raised during the consultation phase, is the question of the potential effects of underwater electrical cables. It is also an issue that is carefully examined by the environmental authority, which evaluates the regulatory impact studies of wind farm projects.
 

Benthos under the microscope

The collaborative SPECIES project, carried out between 2017 and 2020, aimed to answer this question, an essential undertaking given the lack of scientific data available on the subject. Studies as part of this project focused on the potential interactions between the electrical connection cables of MRE projects and benthic organisms (benthos). Benthos live on the seabed, are not very mobile, and would therefore appear to be the most exposed marine organisms. The research was conducted along three main lines: in situ measurement of the physical effects generated by the cables (modification of the habitat, electromagnetic fields, thermal radiation), in situ study of the impact of cable presence on the fauna and flora living on the seabed in coastal areas, and laboratory study of the potential impact of electromagnetic fields on the behaviour of the European lobster (Homarus gammarus) and the scallop (Pecten maximus).

Reassuring results

The project allowed for better characterisation of physical disturbance during the operational phase. The heating generated by cables laid (not buried) on the seabed is negligible, while the intensity of the electromagnetic fields emitted by the various cables studied is weak and localised (around a few nT at 10 m, to a few µT at 2 m, while the earth's magnetic field is around 50 µT at our latitudes). Furthermore, the protective structures of unmoored cables can provide a favourable habitat for many fixed and mobile species, including structural and commercial species. Therefore, no drastic negative impact of submarine power cables on benthic ecosystems has been demonstrated. Nevertheless, the impact of the electromagnetic field, which is apparently weak for the benthos under experimental conditions, remains to be assessed in situ in the most exposed sectors (dense cable networks) before it can be excluded from the debate on environmental concerns associated with MRE projects.
 

Future prospects

The project has been instrumental in developing and testing tools for the measurement of electromagnetic fields at sea and for laboratory experimentation. It has also served to define clear and effective recommendations for studying the impact of electric cables on the invertebrate communities of soft-sediment and rocky seabeds. Research should nevertheless be pursued in order to study in greater depth certain issues that remain insufficiently documented, such as the characterisation of sensitivity thresholds to magnetic fields, or impact accumulation. This is all the more important given that the number and power of submarine cables are set to grow significantly in French coastal waters.

About SPECIES

The SPECIES or Submarine Power Cables Interactions with Environment & associated Surveys project launched in 2016. Coordinated by France Energies Marines and under the scientific direction of Ifremer, the project brought together a consortium of nine academic and private partners with complementary skills and input.

 

This project benefits from State aid managed by the French National Research Agency (ANR) under the Investments for the Future programme, financial support from the members and partners of France Energies Marines and public funding from the Brittany and Normandy regions.