Abstract
Abstract. Ancient Lake Ohrid is a steep-sided, oligotrophic, karst lake that was tectonically formed most likely within the Pliocene 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 60 m water depth. According to our data, significant lake level fluctuations with prominent lowstands of ca. 60 and 35 m below the present water level occurred during Marine Isotope Stage (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 image 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.
Highlights
Within the terrestrial realm, ancient lakes are valuable archives providing crucial information on past climate, environmental conditions, and speciation among endemic taxa
While information on past temperature variability at relatively high spatial resolution has become available during the past decade (Peyron et al, 1998; Allen et al, 1999; Martrat et al, 2004; Hayes et al, 2005; Marino et al, 2009), information on hydrological changes in the northern Mediterranean borderland is relatively sparse over long time scales (Tzedakis et al, 2003; Bordon et al, 2009)
In September 2007 and June 2008 we carried out two multichannel seismic surveys using a small airgun (0.25 l and 0.1 l) and a 100 m-long 16-channel streamer
Summary
Ancient lakes are valuable archives providing crucial information on past climate, environmental conditions, and speciation among endemic taxa. While information on past temperature variability at relatively high spatial resolution has become available during the past decade (Peyron et al, 1998; Allen et al, 1999; Martrat et al, 2004; Hayes et al, 2005; Marino et al, 2009), information on hydrological changes in the northern Mediterranean borderland is relatively sparse over long time scales (Tzedakis et al, 2003; Bordon et al, 2009). In order to gain a better understanding of the variability of hydrologic changes in this climate-sensitive region, additional spatially distributed paleoclimate records must be investigated. Ancient Lake Ohrid can provide such a record in the northern Mediterranean borderland with its sensitivity to recent and past climatic and environmental changes
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