The ~ 220 hectares large and ~ 40 m deep Schliersee is located at around 780 m above sea level in the Bavarian Prealps. It is a popular recreational area and, like the densely populated Alps as a whole, is severely affected by the current climate change. The Schliersee, which is now mesotrophic, has already shown the first effects of human activities in the past, visible in the form of mass developments of cyanobacteria, but also a lack of oxygen in the depths of the water.
In our project, together with colleagues from the Institute of Geography at the Friedrich Schiller University Jena, we want to reconstruct the paleohydrology and development of the body of water over the last ~ 4000 years. At IGeo we primarily use diatoms, which are ideal bioindicators for environmental reconstructions. Their robust and species-specific valves are usually preserved in lake sediments for thousands of years. By analyzing the former diatom species communities, we finally get a picture of the water quality in the past. Since diatoms react very sensitively, especially with regard to nutrient content, anthropogenically caused changes in water quality can be reconstructed particularly well. In our project, we combine taxonomic identification using diatom valve morphology and genetic analyzes such as metabarcoding to reconstruct the diatom communities of the last ~ 4000 years and identify the influences of human activities on the lake. For this purpose, several sediment cores were taken in 2021, 2022 and 2023, covering a total of almost 10 m.
Colleagues from the DSMZ in Braunschweig, who were also involved in the drilling campaigns, are working in parallel on the microbiome of the deeper sediment layers. Sediments are not only excellent archives for paleolimnological or climatic reconstruction, they also harbor active microorganisms on the sediment surface and even at greater sediment depths, which continue to break down the organic material in the sediment and thus intervene in the material cycles, the "deep biosphere". Over a sediment depth of almost 9 m, the research focus is on the one hand on the mutual influence of habitat and microbial community and on the other hand on the potential of microorganisms to serve as paleolimnological proxies.