Coastal seas are valuable habitats for recreational activities and harvestable resources. Exposed to socio-economic pressures at sea and from the watershed, these areas constitute particularly ecologically sensitive and vulnerable zones. One major threat hanging over marine coastal ecosystem health results from increased delivery of anthropogenic nutrients causing eutrophication problems.

The land-based sources of nutrients are considerably enriched in N and P compared to Si due to agricultural, industrial and household activities. Freshwater nutrient sources therefore strongly modify the nutrient chemical forms and the N:P:Si balance of coastal waters with respect to coastal phytoplankton and diatom requirements.

Beyond the diversity of local manifestations, coastal eutrophication results in the shift in species composition of the planktonic community with the occurrence of undesirable non-siliceous phytoplankton some of them being mixotrophs.

ESA research on coastal eutrophication aims to establish the quantitative and qualitative links between nutrient (N, P, Si) enrichment, the spreading of undesirable algal blooms and the associated food web alteration. The approach combines field observations, eco-physiological studies and ecological/biogeochemical modeling with the objective of:

♦ Improving scientific knowledge of eutrophication symptoms and mechanisms;
♦ Building a coastal ecological model as a scientific and management tool;
♦ Assembling a land-coastal ocean biogeochemical model for testing possible future
earth scenarios;
♦ Developing science-based indicators of good ecological status.

The approach is generic and has been/is being applied in different European river eutrophied coastal zones such as:

-The Phaeocystis-dominated Southern North Sea (AMORE, IZEUT)
-The Scheldt river-coastal southern North Sea (IAP TIMOTHY)
-The Seine/Somme/Scheldt -eastern Channel and Southern North Sea (THRESHOLD, AWARE)
-The North East Atlantic Ocean (EMOSEM)
-The Danube river-northwestern Black sea (EROS-21)