Modelling impacts of offshore wind farms on trophic web: the Courseulles-sur-Mer case study

International audienceThe French government is planning the construction of three offshore wind farms in Normandy. These offshorewind farms will integrate into an ecosystem already subject to a growing number of anthropogenic disturbancessuch as transportation, fishing, sediment deposit, and sediment extraction. The possible effects of this cumulativestressors on ecosystem functioning are still unknown, but they could impact their resilience, making themsusceptible to changes from one stable state to another.Understanding the behaviour of these marine coastal complex systems is essential in order to anticipate potentialstate changes, and to implement conservation actions in a sustainable manner. Currently, there are noglobal and integrated studies on the effects of construction and exploitation of offshore wind farms. Moreover,approaches are generally focused on the conservation of some species or groups of species. Here, we developa holistic and integrated view of ecosystem impacts through the use of trophic webs modelling tools. Trophicmodels describe the interaction between biological compartments at different trophic levels and are based on thequantification of flow of energy and matter in ecosystems. They allow the application of numerical methods forthe characterization of emergent properties of the ecosystem, also called Ecological Network Analysis (ENA).These indices have been proposed as ecosystem health indicators as they have been demonstrated to be sensitiveto different impacts on marine ecosystems. We present here in detail the strategy for analysing the potentialenvironmental impacts of the construction of the Courseulles-sur-Mer offshore wind farm (Bay of Seine) such asthe reef effect through the use of the Ecopath with Ecosim software. Similar Ecopath simulations will be made inthe future on the Le Tréport offshore wind farm site.Results will contribute to a better knowledge of the impacts of the offshore wind farms on ecosystems.They also allow to define recommendations for environmental managers and industry in terms of monitoring theeffects of Marine Renewable Energy, not only locally, but also on other sites, national and European levels. Finally,this approach could contribute to a better social acceptability of Marine Renewable Energy projects allowing aholistic vision of all pressures on ecosystem