Eutrophication decreases in European coastal waters

Eutrophication in Europe’s coastal waters, compiled by the European Environment Agency (EEA) evaluates the causes, state and development of eutrophication in the Arctic, Baltic, North, Celtic and Mediterranean seas, and in the Bay of Biscay and Iberian Coast. The report also identifies areas where more monitoring data are needed to improve the assessment, with all countries urged to help reduce serious data gaps on eutrophication by reporting more thoroughly on the status of their coastal waters.

Since the middle of the 1980’s, the phosphorous load entering European seas, in some northern areas by up to 50%, due to improved sewage treatment and phosphate-free detergents, however nitrogen concentrations have remained constant or only slightly decreased, with diffuse pollution from agriculture singled out as a major barrier to reductions.

The report found that the whole coastal as well as open Baltic Sea is affected by eutrophication with enhanced nutrient concentrations and related problems, although levels have decreased since the 1980’s (see related story). The highest loads are found in estuaries and coastal areas close to rivers that drain agricultural and densely populated areas. Nitrogen loads have decreased in the region though, thanks to reduced fertiliser use in countries in transition, such as Poland and the Baltic States.

In the Mediterranean Sea, especially the Adriatic, Gulf of Lion and northern Aegean specific coastal and adjacent offshore areas suffer from eutrophication, sometimes severely. Discharge of untreated or poorly treated wastewater is a major cause especially in enclosed coastal bays with rivers flowing into them, in addition to nutrient loads from agriculture and aquaculture.

In the Greater North Sea, eutrophication primarily affects the coastal zone, in particular in estuaries and fjords such as Wadden Sea, German Bight, Kattegat and eastern Skagerrak. In the Celtic Seas, the phenomenon is problematic in the Bristol Channel, Irish Sea and many estuaries, especially the Mersey, Liverpool Bay, Belfast Lough, Cork Harbour and Dublin Bay.

In the Bay of Biscay and at the Iberian coast, eutrophication problems are restricted to estuaries and coastal lagoons, especially Bay of Vilaine, Arcachon, Rio Formosa and Huelva.