The environmental and evolutionary history of Lake Ohrid (FYROM/Albania): interim results from the SCOPSCO deep drilling project

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 584m 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 460m of this sequence. Tephrochronology and
tuning biogeochemical proxy data to orbital parameters revealed
that the upper 247.8m represent the last 637 kyr. The
multi-proxy data set covering these 637 kyr indicates longterm
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.