Eutrophication symptoms: the English Channel and Southern North Sea

The shallow and well-mixed continental waters northern eastern English Channel and Southern North Sea are submitted to the nutrient inputs by large rivers (Seine, Somme, Scheldt, Rhine/Meuse, Ems-dollar, Elbe) that cumulate along the SW-NE direction (Lancelot et al., 1987).

Scheldt estuary

Scheldt river system (credit: Wikimedia Commons)

These nutrient inputs show a large excess of nitrates that is beneficial to Phaeocystis colonies. Due to their large size these colonies are not grazed by zooplankton (loss for secondary production) and accumulate in the water column causing foam accumulation and bottom oxygen deficiency in some areas.

Phaeocystis globosa

Left: Phaeocystis globosa colony (credit: T.Nandakumar). Right: Foam accumulation produced by the degradation of Phaeocystis globosa colonies (credit: Wikimedia Commons)

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Lancelot, C., Billen, G., Sournia, A., Weisse, T., Colijin, F., Veldhuis, M.J.W., Davies, A. and Wassman, P., 1987. Phaeocystis blooms and nutrient enrichment in the continental coastal zones of the North Sea. Ambio, 16(1): 38- 46.