Research project summary
Coastal eutrophicaPon 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 generaPng a large amount of study, in the context of generalized
warming waters, which reinforces the consequences of eutrophicaPon. This global challenge
is the result of local anthropogenic pressures and forcings, which depend on the characterisPcs
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 producPvity, and ecological services associated with it. Because of their interface
posiPon, these ecosystems also concentrate pressures from human acPviPes, which endanger
their funcPoning and their ability to support the services they offer. Among the various
anthropogenic disturbances affecPng coastal ecosystems, agricultural acPviPes and
wastewater discharges lead to massive inputs of nutrients such as nitrogen (N) and
phosphorus (P). Excessive inputs are at the origin of eutrophicaPon, 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 quanPfy the impact of dystrophy, using a mulP-scale approach,
in a context of significant water warming, on the structure and composiPon of phytoplankton
communiPes (specific and funcPonal diversity, size structure, etc.) and the consequences for
pelagic primary producPon and associated carbon fluxes. A retrospecPve analysis of in situ
observaPon series will be carried out in associaPon with an experimental approach that will
couple work in microcosms on natural communiPes 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 communiPes.