Designing optimal scenarios of nutrient loading reduction in a WFD/MSFD perspective by using passive tracers in a biogeochemical-3D model of the English Channel/Bay of Biscay area

To verify this quick linear approach restricted to winter nutrients, a full non-linear, coupled biogeochemical-hydrodynamical model has been used to compute the effect of these optimal nutrient reduction scenarios on the most characteristic descriptors of eutrophication: chlorophyll 90th percentile, dinoflagellate maximum and bottom oxygen concentration 10th percentile. The results show that nutrient loading reductions enabling a Good Ecological Status everywhere for winter marine nutrients would still leave some marine areas in a Bad Ecological Status in terms of chlorophyll content.