PAST AND RECENT EUTROPHICATION TRENDS OF SCHWERINER SEE, NE-GERMANY – A COMBINED SEDIMENTOLOGICAL AND GEOCHEMICAL APPROACH OF SURFACE SEDIMENT SAMPLING AND SEDIMENT CORE ANALYSIS

Schweriner See is a eutrophic post-glacial lake in Mecklenburg-Vorpommern, NE-Germany. It is the fourth largest lake in Germany and was formed after the Last Glacial Maximum. The lake consists of two basins, a northern basin called Außensee, and a southern basin called Innensee, which are separated by a semi-artificial dam. Previous studies on sediment cores from the northern basin revealed increased eutrophication and contamination trends throughout the basin, starting in 1900 CE when a sewage plant was built that disposed sewage directly into Schweriner See. These trends are related to the population dynamics of the city of Schwerin, located on the southeastern shore of the Innensee. Eutrophication in Außensee peaked in the 1970s, and began to improve in the 1990s, probably due to the completion of a new sewage plant that does not discharge sewage into the lake, a population decrease and the introduction of phosphate-free washing both caused by the German Reunification.

Eutrophication trends observed in the Außensee are thought to be similar to the eutrophication trends in the Innensee. To connect the eutrophication history of both basins, this study analyzed sediment cores taken approx. 700 m away from the former sewage plant in Innensee, which will be compared to the sediment cores from the previous study. As both lake basins have a complex bathymetry and the grasp of the spatial distribution of sediment components is limited, we sampled surface sediment at a spatial distribution of approx. 1.2 km apart from 0.5 m to 45 m water depth. This study aims to improve the understanding of internal lake dynamics by looking at the distribution of sedimentary pigments (e.g., Chl-a) derived from spectrophotometer measurements, organic matter content by LOI (550 °C), carbonate content and XRF measurements. This combined approach will give an insight in past and present eutrophication trends and sedimentation dynamics of the entire Schweriner See.