Late Quaternary climatic and environmental history of
Lake Ohrid


Martin Melles



Bernd Wagner
Institute für Baltic Sea Research Warnemünde (IOW), Germany

Antje Schwalb
University Braunschweig, Germany
Gerhard Daut
University Jena, Germany

Martin Wessels
Institute for Lake Research, Langenargen, Germany
André Lotter, Oliver Heiri
Utrecht University, The Netherlands
Zoran Spirkovski
Hydrobiological Institute, Ohrid, Macedonia
M. Sanxhaku
Institute of Hydrometeorolgy, Tirana, Albania


Funding:
Deutscher Akademischer Austausch Dienst (DAAD)
Deutsche Forschungsgemeinschaft (DFG)



Scientific background

 
Lake Ohrid is located at the Macedonian/Albanian border between 40°54' and 41°10' N. With a length of c. 30 km and a width of c. 15 km, the lake surface area measures c. 360 km2, two thirds of which belong to Macedonia and one third, the southwestern part of the lake, to Albania. The bathymetric maps existing from the lake show a maximum water depth of almost 300 m. More than 200 endemic species reveal the uniqueness of Lake Ohrid. This great number of endemic species, mainly formed by invertebrates and algae, but also by some fishes, indicates that the overall environmental conditions have been stable over a long period. Biological and biogeographical studies suggest that the origin of Lake Ohrid dates back to Early Quaternary or Pliocene times, about one to five million years ago. Despite the knowledge about the immense age of the lake, investigations of its sedimentary record in order to reconstruct the regional climatic and environmental history are scarce.


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Map of Albania and Macedonia, indicating the location of Lake Ohrid. The inlet shows a satellite image of Lake Ohrid.


Aims

Main objectives of the international research project at Lake Ohrid are to understand regional differences in sedimentation rates and sediment composition, to reconstruct its Late Quaternary history in relation to that of the central and eastern Mediterranean region, and to investigate its potential for paleoenvironmental reconstructions down to the Tertiary.


First results


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Surface sediment coring at Lake Ohrid in spring 2004.

A shallow seismic survey was carried out on Lake Ohrid in spring 2004 in order to evaluate representative coring locations for future work. First results evidence that the sediments of Lake Ohrid are highly affected by mass movement processes. These processes at least partly were triggered by neotectonic activity, which is suggested by distinct thrusts and folds occurring in the lake sediments. Slumps, debris flows and turbidites are common along the lake slopes, but also occur in parts of the lake center. Other areas of the central lake, however, exhibit obviously undisturbed sediment sequences ideal for recovering continuous sediment records. In addition, hiatuses associated with the mass movement events in some slope areas excavated relatively old sediments so close to the surface that they may be reached with conventional light coring technique.

During a first coring campaign in March/April 2005 sediment sequences of up to ten meter were recovered. According to first readiocarbon dates from the longest core it obviously penetrated back deeply into the last glacial period. Furthermore, a transect of short cores crossing the lake from north to south has been correlated based on core descriptions and first sedimentological results. The data reflect changes in subrecent sedimention rates, with the by far highest sediment input occurring from the south and being predominantly deposited close to the lake shore.



Shallow seismic profile from Lake Ohrid

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Part of a shallow seismic profile from Lake Ohrid, illustrating numerous mass movement processes along the slopes, as well as thrusts and faults which pervade the sediments.


Perspectives

The research groups currently working on Lake Ohrid were brought together during an international workshop held at the University Leipzig in Dec. 2005. On this workshop, which was financially supported by the German Academic Exchange Service (Deutscher Akademischer Austausch Dienst, DAAD), 24 participants from 7 countries summarized the existing results from hydrological, biological and geological investigations at Lake Ohrid, and discussed the perspectives for joint future work. It was agreed that Lake Ohrid has a great potential to supply important information on the long-term climatic, tectonic and volcanic history in the eastern Mediterranian region. Applications for a deep drilling operation to recover the entire lake sediment record, for instance wihin the scope of the International Continental Scientific Drilling Program (ICDP), however, require additional site survey work that involves (i) studies of the processes of modern lake sediment formation, (ii) geomorpholocal research in lake catchment, (iii) additional shallow seimic and first deep seismic investigations of the lake sediments, and (iv) additional shallow coring and complex investigations of the core material.
Workshop Participants

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Participants on the international "Lake Ohrid Workshop" held at the University Leipzig in Dec. 2005