COASTAL EUTROPHICATION - CAUSES, CONSEQUENCES AND PERSPECTIVES IN THEARCHIPELAGO AREAS OF THE NORTHERN BALTIC SEA

Coastal eutrophication has, since the early 1970s, become the foremost threat to the marine ecosystem of the Archipelago Sea (the Aland Isla nds and the SW Finnish archipelago) in the northern Baltic Sea. Nutrie nt levels (N, P) have risen significantly both in coastal areas and ba sin-wide, which has led to increased primary production (both pelagic and benthic), decreased transparency, increasing amounts of oxygen-con suming drift-algal mats at shallow and intermediate bottoms, and chang es in zoobenthos and fish communities. Local nutrient input originates mainly from agriculture, riverine input, municipal wastewaters, aquac ulture and airborne loading. Levels indicate an even distribution of n utrients from the inner areas to the open coast, reducing the natural diluting or filtering effects of the mosaic archipelago system. Future prospects for the archipelago and coastal ecosystem are poor unless l ocal and regional measures to drastically reduce nutrient levels of th e archipelago are undertaken. Even then, positive effects are unlikely to show immediately. (C) 1997 Academic Press Limited.