Pelagic and benthic trophic chain coupling in a semi-enclosed coastal system, the Bay of Brest (France): a modelling approach

During the 2 last decades several studies have analysed the response of phy toplankton dynamics and benthic trophic webs to increasing anthropogenic eu trophic conditions in the Bay of Brest, France. The present project couples 2 models, a pelagic and a benthic one, to synthesise both these approaches to this ecosystem. This model shows that in spite of net carbon production being more than 10-fold lower than phytoplankton production benthic suspen sion feeders partly control the phytoplankton dynamics in the Bay. Computat ion of the nitrogen fluxes reveals the role of the benthic trophic chain in nutrient recycling. It is possible to show that an increase in nitrogen lo ading in the Bay would have limited consequences on the ecosystem, with the excess nitrogen being transferred to shelf waters without entering the tro phic chain. The problem of toxic bloom events that can affect benthic suspe nsion feeders, and consequently the total ecosystem, will have to be thorou ghly studied.