Subsea power cables are present throughout our oceans and serve a variety of purposes: connecting islands to the mainland for energy distribution, connecting stand-alone power grids, powering offshore platforms, as well as transporting the power produced by offshore renewable energy (ORE) installations to shore. In 2015, the total length of high-voltage direct current (HVDC) cables on the seabed worldwide was estimated to be 8,000 km, with 70% of these cables being located in European waters (Ardelean and Minnebo, 2015).
Europe also accounted for 5,047 offshore wind turbines at the end of 2019, representing 22.1 GW, with 25 GW planned for 2025 (WindEurope, 2020). Given this exponential development of ORE projects, the number of subsea power cables is increasing considerably. Like any human installation or activity at sea, these cables can cause disruptions to marine life and habitats. However, and despite the fact that they have been present in our oceans since the mid-twentieth century, very few scientific publications address the effects of these power cables on the marine environment (Taormina et al., 2018; Carlier et al., 2019). With the current increase in the number of cables, there is today an urgent need to characterise their potential impacts on marine ecosystems.
It is within this framework that the collaborative project “SPECIES” (“Submarine PowEr Cables Interactions with Environment & associated Surveys”) was launched in 2016. The aim of this project was to improve knowledge of the potential interactions between the electric power cables of ORE projects and benthic organisms, which would appear to be the most exposed communities. Coordinated by France Energies Marines and scientifically led by Ifremer, the project brought together a consortium of nine academic and private partners with complementary skills and contributions.
The research was conducted along three main lines:
- In situ measurements of the physical effects generated by the cables (e.g., emission of electromagnetic fields, thermal radiation) at different ORE test sites or interconnections in France.
- The study, via in situ approaches, of the potential impact of these cables on coastal benthic communities, focusing on different biological compartments (e.g., endofauna, epibenthic communities and crustaceans/fish among benthic megafauna) at different sites in France.
- The study of the potential impact of the cables, and in particular of electromagnetic fields, on the behaviour of certain notable benthic species, using experimental approaches in the laboratory.
The aim of this report is to provide a synthesis of the results of the SPECIES project and the perspectives arising from it. It is divided into six parts:
- A summary of the different effects that can be generated by subsea power cables.
- An overview of the selected study sites.
- Fact sheets covering several scientific questions, and presenting the methods developed and implemented as well as the main results of the project.
- Feedback on the difficulties encountered and the resulting methodological recommendations.
- A review of the project for managers and stakeholders in the ORE sector.
- Perspectives for future research on the same topic.