Changes in the composition of the diatom flora during the last century indicate increased eutrophication of the oder estuary, south-western Baltic Sea

Four short sediment cores from the Oder estuary, south-western Baltic Sea, were studied with respect to their siliceous microfossil and organic carbon content. The sediments were dated by Pb-210. The objective was to detect a nd date changes in the composition of the diatom flora and link these chang es to increased human impact in the drainage area during recent centuries. Two of the cores showed an unperturbed sedimentary sequence representing a complete historical record. A change in the composition of the diatom assem blages attributable to anthropogenic factors was recorded. This was dated t o about 1900 in the Oderhaff. The change consisted of an increase in specie s that thrive in eutrophic waters and those indicating increased salinity o r the availability of inorganic nutrients. (C) 1999 Academic Press.