Abstract
Abstract. Organic matter preserved in Lake Ohrid sediments originates from aquatic and terrestrial sources. Its variable composition reflects climate-controlled changes in the lake basin's hydrology and related organic matter export, i.e. changes in primary productivity, terrestrial plant matter input and soil erosion. Here, we present first results from lipid biomarker investigations of Lake Ohrid sediments from two near-shore settings: site Lz1120 near the southern shore, with low-lying lands nearby and probably influenced by river discharge, and site Co1202 which is close to the steep eastern slopes. Variable proportions of terrestrial n-alkanoic acids and n-alkanols as well as compositional changes of ω-hydroxy acids document differences in soil organic matter supply between the sites and during different climate stages (glacial, Holocene, 8.2 ka cooling event). Changes in the vegetation cover are suggested by changes in the dominant chain length of terrestrial n-alkanols. Effective microbial degradation of labile organic matter and in situ contribution of organic matter derived from the microbes themselves are both evident in the sediments. We found evidence for anoxic conditions within the photic zone by detecting epicholestanol and tetrahymanol from sulphur-oxidising phototrophic bacteria and bacterivorous ciliates and for the influence of a settled human community from the occurrence of coprostanol, a biomarker for human and animal faeces (pigs, sheep, goats), in an early Holocene sample. This study illustrates the potential of lipid biomarkers for future environmental reconstructions using one of Europe's oldest continental climate archives, Lake Ohrid.
Highlights
Lake Ohrid is special for a number of reasons
Our study presents a first inventory of lipid biomarkers present in total lipid extracts from Holocene and glacial sediments of ancient Lake Ohrid
Significant amounts of labile unsaturated lipids were only found in the surface sample reflecting effective degradation of these compounds with depth
Summary
Lake Ohrid is special for a number of reasons. As one of the oldest lakes in the World it potentially preserves the oldest continuous archive of environmental change in Europe, dating back 3–5 million years (Wagner et al, 2008, 2009). It hosts more than 200 endemic species which makes it a unique ecosystem in Europe and, taking its size into account, is the most diverse lake in the world (Albrecht and Wilke, 2008) It is situated in an intramontaneous basin that belongs to one of only three Mediterranean refugia that were vital for the survival of important groups of plants such as deciduous trees through the hostile climate conditions of the Pleistocene glaciations; the other two were on the southern Iberian Peninsula and in southern Italy (Brewer et al, 2002). The sediments of Lake Ohrid provide a unique archive for the reconstruction of environmental change in high-resolution
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