Résumé
Effects of watershed management upon particulate and dissolved matter transfers and upon quality of surface water, in agricultural areas. This research deals with relationships between landscape characteristics and management, fluxes of particulate matter and nutrients emitted and transferred to the hydrographic network and resulting ecological impacts on river systems. The study was focused on a set of small rural watersheds at scales ranging from from 50 ha to 500 ha , drained by brooks more or less protected by riparian corridors. Stream ecosystems are exposed to various level of disturbance mainly related to their nutrients and particulate matter loads.Hydrological conditions, land uses, distribution of active areas within the watersheds determine the fluxes of nutrients and particulate matter which were more or less buffered by the existing riparian areas according to their management. Responses of receiving ecosystems have been measured thanks to a multi bio indicator analysis (including macro-invertebrate, macrophyte and diatom communities, biofilm enzymatic activities, zebra mussel, brown trout, ...). We have attempted to linked variability of responses to the working of the watershed and distribution patterns of active areas and buffer zones. Some key processes of stream ecology have been studied experimentally (behaviour of trout larval phase, ecophysiology of trout eggs).