Precising target NO3 concentrations to limit green algae blooms in Brittany

Green macroalgae blooms are a widespread manifestation of coastal eutrophication. In most cases, N inputs by rivers are the main anthropogenic cause. In Brittany, a severely impact region in France, first studies recommended a target NO3 streamwater concentration around 2.5 mg/L to limit the blooms.

After two decades of decrease, although the concentrations remain well above this target, bloom limitations occurred recently, under specific climatic conditions. Coupling the ecological model MARS-ULVES with the agro-hydrological model TNT2 allowed testing contrasted climate sequences and precising the target concentrations for future policy.