Modélisation du réseau trophique pélagique et de la production primaire en Manche

This paper deals with a model of the pelagic ecosystem in the English Channel The model takes into account nitrogen biogeochemical cycle explicitly and indirectly phosphorus, silicon and carbon ones. The pelagic ecosystem is described precisely, on the one hand with the help of three phytoplanktonic compartments, and the other by considering the microbial food web. Primary production appears to be mainly controlled by stratification and turbidity, except in the Bay of Seine where high terrestrial nutrient inputs generate a sharp enrichment. Moreover, the model allows some general ecological conclusions to be drawn. From the simulation, it appears that inorganic nitrogen in the water column is mainly produced by an intense recycling. In accordance with in situ measurements, these results tend to demonstrate the predominance of the regenerated production over the new one in the English Channel. Simulation of nitrogen fluxes on an annual basis underlines the importance of bacterial remineralization, underestimating microzooplanktonic excretion in the recycling of elements. Furthermore, exchanges between pelagic and benthic compartments appear to be weak.