As part of the energy transition, the French government is planning the construction of three offshore wind farms in Normandy (Bay of Seine and eastern part of the English Channel, north-western France) in the next years. These offshore wind farms will be integrated into an ecosystem already facing multiple anthropogenic disturbances such as maritime transport, fisheries, oyster and mussel farming, and sediment dredging. Currently, no integrated, ecosystem-based study on the effects of the construction and exploitation of offshore wind farms exists, biological approaches being generally focused on the conservation of some valuable species or groups of species. Complementary trophic web modelling tools were applied to the Bay of Seine ecosystem to analyse the potential impacts of benthos and fish aggregation caused by the introduction of additional hard substrates from the piles and the turbine scour protections. An Ecopath model composed of 37 compartments, from phytoplankton to seabirds, was built to describe the situation “before” the construction of the offshore wind farm. Then, a projection over the next 30 years was performed after increasing the biomass of some targeted benthic and fish compartments in this model.
Main results showed (1) that the total ecosystem activity, the overall system omnivory (proportion of generalist feeders), and the recycling increased after the construction of the offshore wind farm, (2) that higher trophic levels such as piscivorous fish species, marine mammals and seabirds responded positively to the aggregation of biomass on piles and turbine scour protections; and (3) a change in keystone groups after the construction towards more structuring and dominant compartments. Nonetheless, these changes could be considered as limited impacts of the wind farm installation on this coastal trophic web structure and functioning.
* Raoux A, Tecchio S, Pezy JP, Lassalle G, Degraer S, Wilhelmsson D, Cachera M, Ernande B, Le Guen C, Haraldsson M, Grangeré K, Le Loc’h F, Dauvin JC, Niquil N (2017). Benthic and fish aggregation inside an offshore wind farm: Which effects on the trophic web functioning? Ecological Indicators 72: 33-46
Contact: Nathalie Niquil, nathalie.niquil@unicaen.fr