Clara MASSINOT

DYSTRO-B Project

Coastal eutrophication caused by anthropogenic inputs of nutrients is one of the greatest threats to the health of estuarine and coastal ecosystems worldwide. This issue reflects a global challenge that is generating a large amount of study, in the context of generalized warming waters, which reinforces the consequences of eutrophication. This global challenge is the result of local anthropogenic pressures and forcings, which depend on the characteristics of local ecosystems (coastline morphology, currents, depth, turbidity, watersheds, etc.) as well as the socio-economic environment of the coastal zone and watersheds.

Indeed, at the interface of terrestrial and marine provinces, coastal and estuarine ecosystems promote high biological productivity and the ecological services associated with it. Because of their interface position, these ecosystems also concentrate pressures from human activities, which endanger their functioning and their ability to support the services they offer. Among the various anthropogenic disturbances affecting coastal ecosystems, agricultural activities and wastewater discharges lead to massive inputs of nutrients such as nitrogen (N) and phosphorus (P). Excessive inputs are at the origin of eutrophication, which results in a significant increase in the biomass of primary producers, such as planktonic microalgae, and is one of the most observed effects, in the English Channel and in other parts of the world.

This project aims to qualify and quantify the impact of dystrophy, using a multi-scale approach, in a context of significant water warming, on the structure and composition of phytoplankton communities (specific and functional diversity, size structure, etc.) and the consequences for pelagic primary production and associated carbon fluxes. A retrospective analysis of in situ observation series will be carried out in association with an experimental approach that will couple work in microcosms on natural communities from three sites in the Bay of Seine, with studies on isolated monoclonal cultures in the Channel belonging to the main strains and different size classes of the Bay's communities.