Potential effect of nitrogen from rivers on the marine phytoplankton between Roscoff and Saint-Brieuc

A first version of a digital model of a coastal ecosystem developped in North Brittany between Roscoff and Saint-Brieuc is described. Designed for impact studies and taking into account a meterological time scale of over 20 years, this model simulates the daily changes in water temperature, salinity, phytoplanktonic biomass and nitrogen, with spacing of 2 km. After indicating the principal adjustment phases of the model and actions planned to improve its descriptive quality, an application of the latter is given showing possible consequences of nitrogen from the coastal rivers, in an agricultural region with heavy use of fertilizers, on the development of marine phytoplankton.