Seafloor anoxia and modern laminated sediments in coastal basins of the Eastern Gulf of Finland, Baltic Sea

Abstract

Examination of surface sediment cores from the northern coastal basins of the eastern Gulf of Finland, the Baltic Sea, revealed that almost all of the studied basins have been continuously or seasonally anoxic for at least the last 10 years. This can be seen as rather similar laminated sequences in the topmost parts of the sediment cores. Moreover the results indicate an overall shallowing of anoxia since 1950's in the coastal area of the eastern Gulf of Finland. Towards the present, laminated sediments were developed also in the shallower basins. Extend ed and prolonged seafloor anoxia could enhance the environmental problems by releasing metals and nutrients, like P, from the seafloor sediments. Anoxic periods at the scafloor of the Baltic Sea have occurred in the past too, but together with increased anthropogenic loading, its effects to the Baltic Sea ecosystem are harmful.