During the 2 last decades several studies have analysed the response of phytoplankton dynamics and benthic trophic webs to increasing anthropogenic eutrophic 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 suspension feeders partly control the phytoplankton dynamics in the Bay. Computation 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 loading in the Bay would have limited consequences on the ecosystem, with the excess nitrogen being transferred to shelf waters without entering the trophic chain. The problem of toxic bloom events that can affect benthic suspension feeders, and consequently the total ecosystem, will have to be thoroughly studied.