Benthos

The benthos is an important and vulnerable compartment of the ecosystem

The benthos includes all organisms that live in relation to the seabed. This compartment has a very important role in the functioning of marine ecosystems. It is in fact a food source for many species at higher trophic levels and a major player in carbon recycling. The benthos is very diverse and is mainly made up of invertebrates (crustaceans, molluscs, bryozoans, corals, etc.) and algae (kelp, green and red algae, etc.). It also includes various fishes and elasmobranchs (sharks and rays). The organisms that make up the benthos are subject to many anthropogenic pressures (fishing, biological invasion, global changes, extraction of aggregates, pollution) and are particularly vulnerable because they are not very mobile.

Estimating the changes induced by the deployment of ORE

Deployment of ORE can potentially result in changes to the natural functioning of the benthic compartment that may be perceived as “positive” or “negative” for the ecosystem. The pressures generated by offshore renewable energies are diverse and change over the life of the projects. Indeed, the installation of structures leads to physical disturbances of the seabed, such as modification of the sedimentary bed or the use of a natural substrate surface that directly impact the benthos. This work also leads to the emission of noise into the marine environment, disturbing sensitive species in the vicinity.  During the operational phase, ORE systems act like artificial reefs and are colonised by a wide variety of living organisms. These may attach directly to the structures (such as molluscs and barnacles) or use the shelters created (fishes and large crustaceans) to protect themselves from predators and strong currents. The exclusion of marine activities in certain areas to protect sensitive ORE components such as power cables may result in the creation of reserve areas where benthic organisms are then protected. In addition, electromagnetic fields, emitted by these export cables to their vicinity, can potentially disrupt the behaviour of certain magnetically sensitive organisms such as sharks and rays. The responses of the benthos to these various ecosystem modifications are poorly understood to date. However, it is important to estimate the changes induced in order to be able to propose measures to avoid or reduce the risks associated with ORE projects.

Better understanding and anticipating the effects of ORE on benthos

France Energies Marines explores various topics related to the interactions between benthos and offshore renewable energies. Part of the R&D is aimed at better understanding the composition and functioning of specific ecosystems in order to anticipate the effects of ORE. A collaborative project is underway on the dynamics of benthic communities associated with underwater dunes, a little-known ecosystem concerned by the development of several offshore wind farm projects (DUNES project). Some studies are more focused on the effects associated with the installation phase of the farms. This is notably the case of a project that aims to better understand the acoustic impacts of ORE on benthic communities (BENTHOSCOPE2 project). France Energies Marines also coordinates and carries out complementary research work related to the exploitation phase of ORE: study of the impact of subsea power cables on benthos (SPECIES project), qualitative and quantitative characterisation of biofouling according to the sites and components concerned (ABIOP, ABIOP+ projects) and development of ecosystem approaches integrating benthic communities to characterise the effects of ORE (TROPHIK, APPEAL projects).

The recent launch of DRACCAR, the first French research platform at sea dedicated to offshore wind power, coupled with an innovative R&D programme, will improve the understanding of the interactions between offshore wind power and the environment, the optimisation of the design of wind turbines and allow co-construction of a permanent observation network of the seafronts.

List of publications related to benthos (PDF)

Photo credit: Olivier Dugornay / Ifremer

Interlocutors

Nolwenn Quillien

Benthic Ecology Researcher

News

Published on 12/05/2023

Launch of DRACCAR

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