Abstract
Abstract. This study reviews and synthesises existing information generated within the SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) deep drilling project. The four main aims of the project are to infer (i) the age and origin of Lake Ohrid (Former Yugoslav Republic of Macedonia/Republic of Albania), (ii) its regional seismotectonic history, (iii) volcanic activity and climate change in the central northern Mediterranean region, and (iv) the influence of major geological events on the evolution of its endemic species. The Ohrid basin formed by transtension during the Miocene, opened during the Pliocene and Pleistocene, and the lake established de novo in the still relatively narrow valley between 1.9 and 1.3 Ma. The lake history is recorded in a 584 m long sediment sequence, which was recovered within the framework of the International Continental Scientific Drilling Program (ICDP) from the central part (DEEP site) of the lake in spring 2013. To date, 54 tephra and cryptotephra horizons have been found in the upper 460 m of this sequence. Tephrochronology and tuning biogeochemical proxy data to orbital parameters revealed that the upper 247.8 m represent the last 637 kyr. The multi-proxy data set covering these 637 kyr indicates long-term variability. Some proxies show a change from generally cooler and wetter to drier and warmer glacial and interglacial periods around 300 ka. Short-term environmental change caused, for example, by tephra deposition or the climatic impact of millennial-scale Dansgaard–Oeschger and Heinrich events are superimposed on the long-term trends. Evolutionary studies on the extant fauna indicate that Lake Ohrid was not a refugial area for regional freshwater animals. This differs from the surrounding catchment, where the mountainous setting with relatively high water availability provided a refuge for temperate and montane trees during the relatively cold and dry glacial periods. Although Lake Ohrid experienced significant environmental change over the last 637 kyr, preliminary molecular data from extant microgastropod species do not indicate significant changes in diversification rate during this period. The reasons for this constant rate remain largely unknown, but a possible lack of environmentally induced extinction events in Lake Ohrid and/or the high resilience of the ecosystems may have played a role.
Highlights
Systematic limnological studies started in the early 20th century and were first carried out in Europe, for example at Lake Geneva (e.g. Forel, 1901), a number of lakes in Germany (e.g. Thienemann, 1918), and at Lake Ohrid on the Balkan Peninsula
The aim of this paper is to review and synthesise the results of the 14 individual papers of this special issue and to complement them with information from former and new studies in order to provide a comprehensive overview on progress towards achieving the four main aims defined for SCOPSCO
Based on spectral gamma ray (SGR) from borehole logging, magnetic susceptibility (MS) from core logging, and total inorganic carbon (TIC) analyses on core catcher samples from the DEEP site, and by comparing these data with global climate records such as the benthic isotope stack LR04 (Lisiecki and Raymo, 2005), a minimum age of 1.2 Ma has been proposed for the permanent lake phase of Lake Ohrid (Wagner et al, 2014)
Summary
Systematic limnological studies started in the early 20th century and were first carried out in Europe, for example at Lake Geneva (e.g. Forel, 1901), a number of lakes in Germany (e.g. Thienemann, 1918), and at Lake Ohrid on the Balkan Peninsula (reviewed in Stankovic, 1960). Analytical and technological advances in the following decades facilitated a more comprehensive understanding of the interactions between catchment dynamics, hydrology, and the living world of lakes This led to the establishment of new institutions, such as the Hydrobiological Institute at Lake Ohrid in 1935 (Stankovic, 1960). Besides analyses in extant lakes, early scientists were interested in studying past changes in lake systems, and palaeolimnology, a sub-discipline of limnology, was established in the 1920s. This field started with the collection of sediment cores from lakes to interpret stratigraphic data on plant and animal fossils as a record of the lake’s history (National Research Council, 1996). With the establishment of radiometric dating methods in the 1950s and 1960s, palaeolimnological studies developed into a powerful tool for long- and short-term reconstructions of the climatic and environmental history of lakes and their catchments
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