Eutrophication and heavy metal pollution in the Flensburg Fjord: A reassessment after 30 years.

A study of surface sediment organic matter and heavy metal content (e.g. Cu, Zn, Pb and Sn) was carried out in 2006 to assess changes in eutrophication and pollution in the periodically anoxic Flensburg Fjord since 1972. Low hydrodynamic activity together with sewage discharges and high primary production in the inner fjord promote the enrichment of present day surface sediments in organic matter and metals in contrast to the outer fjord. However, heavy metal contents in the fjord are typical for the western Baltic Sea, although they are higher than in the preindustrial period. Although the anthropogenic nutrient load has substantially decreased since the 1970s, sediments from the inner fjord contain more organic material in 2006 than in 1972 resulting from still high levels of primary production supported by internal nutrient loading. Of the heavy metals measured, a decrease in Pb content since the 1970s is distinct, which is explained by the banning on gasoline lead. Taken together, these results suggest that the amelioration of environmental conditions needs time but is indeed related to reduced anthropogenic inputs.