Stratigraphic analysis of lake level fluctuations in Lake Ohrid: an integration of high resolution hydro-acoustic data and sediment cores
1Leibniz-Institute for Marine Sciences, IFM-GEOMAR, Cluster of Excellence: The Future Ocean, Christian-Albrecht-University, Kiel, Germany
2Institute for Geology and Mineralogy, University of Cologne, Cologne, Germany
3Institute of Geography, University of Cologne, Cologne, Germany
4Geoscience Department at University of Bremen, Bremen, Germany
5Institute for Lake Research, LUBW, Langenargen, Germany
6Institute for Geography, Friedrich Schiller University, Jena, Germany
Abstract. Ancient Lake Ohrid is a steep sided, oligotrophic, karst lake of likely Pliocene age and often referred to as a hotspot of endemic biodiversity. This study aims on tracing significant lake level fluctuations at Lake Ohrid using high-resolution acoustic data in combination with lithological, geochemical, and chronological information from two sediment cores recovered from sub-aquatic terrace levels at ca. 32 and 55 m. According to our data, significant lake level fluctuations with prominent lowstands of ca. 60 and 35 m below the present water level occurred during MIS 6 and MIS 5, respectively. The effect of these lowstands on biodiversity in most coastal parts of the lake is negligible, due to only small changes in lake surface area, coastline, and habitat. In contrast, biodiversity in shallower areas was more severely affected due to disconnection of today sub-lacustrine springs from the main water body. Multichannel seismic data from deeper parts of the lake clearly imaged several clinoform structures stacked on top of each other. These stacked clinoforms indicate significantly lower lake levels prior to MIS 6 and a stepwise rise of water level with intermittent stillstands since its existence as water filled body, which might have caused enhanced expansion of endemic species within Lake Ohrid.