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Marine Ecology Progress Series

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MEPS 189:135-147 (1999)  -  doi:10.3354/meps189135

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

O. Le Pape1,*, F. Jean2, A. Ménesguen3

1IFREMER-RH, Avenue du Général de Gaulle, 14520 Port en Bessin, France
2UMR 6539, Ecologie benthique, IUEM, Place Nicolas Capesnic, 29280 Plouzané, France
3IFREMER-DEL, BP 70, 29280 Plouzané, France

ABSTRACT: 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.

KEY WORDS: Eutrophication · Dynamic simulation model · Bay of Brest · Hydrodynamism · Phytoplankton · Benthos

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