Sediment core fossils in ancient Lake Ohrid: testing for faunal change since the Last Interglacial

Abstract

Abstract. Ancient Lake Ohrid is probably of early Pleistocene or Pliocene origin and amongst the few lakes in the world harbouring an outstanding degree of endemic biodiversity. Although there is a long history of evolutionary research in Lake Ohrid, particularly on molluscs, a mollusc fossil record has been missing up to date.For the first time, gastropod and bivalve fossils are reported from the basal, calcareous part of a 2.6 m long sediment succession (core Co1200) from the north-eastern part of Lake Ohrid. Electron spin resonance (ESR) dating of mollusc shells from the same stratigraphic level yielded an age of 130 ± 28 ka. Lithofacies III sediments, i.e. a stratigraphic subdivision comprising the basal succession of core Co1200 between 181.5-263 cm, appeared solid, greyish-white, and consisted almost entirely of silt-sized endogenic calcite (CaCO 3 >70%) and intact and broken mollusc shells. Here we compare the faunal composition of the thanatocoenosis with recent mollusc associations in Lake Ohrid. A total of 13 mollusc species (9 gastropod and 4 bivalve species) could be identified within Lithofacies III sediments. The value of sediment core fossils for reconstructing palaeoenvironmental settings was evaluated and the agreement between sediment and palaeontological proxies was tested.The study also aims at investigating major faunal changes since the Last Interglacial and searching for signs of extinction events.The combined findings of the ecological study and the sediment characteristics suggest deposition in a shallow water environment during the Last Interglacial. The fossil fauna exclusively included species also found in the present fauna, i.e. no extinction events are evident for this site since the Last Interglacial. The thanatocoenosis showed the highest similarity with recent Intermediate Layer (5-25 m water depth)Correspondence to: C. Albrecht (christian.albrecht@allzool.bio.uni-giessen.de) mollusc assemblages. The demonstrated existence of a mollusc fossil record in Lake Ohrid sediment cores also has great significance for future deep drilling projects. It can be hoped that a more far reaching mollusc fossil record will then be obtained, enabling insight into the early evolutionary history of Lake Ohrid.

Sedimentary and tectonic evolution of Lake Ohrid (Macedonia/Albania)

“…Inactivity of the karst springs during the glacial periods due to permafrost in large parts of the carbonate-dominated mountains has been suggested by a multi-proxy analysis of ostracods, pollen, sedimentology and tephro-chronology (Belmecheri et al, 2009;L ezine et al, 2010), but this has not been confirmed by other studies (e.g. Analysis of biomarkers and molluscs reveal major changes within the faunal and vegetation cover since the Last Interglacial (Albrecht et al, 2010;Holtvoeth et al, 2010). comm.).…”

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

“…Some of the sediment sequences were also studied for their fossil diatom, pollen, ostracod, or mollusc compositions. The sample preparation for the micro-and macrofossil analyses and the determination of the taxa are described in detail in the individual publications (Belmecheri et al, 2009(Belmecheri et al, , 2010Wagner et al, 2009Wagner et al, , 2014Albrecht et al, 2010;Reed et al, 2010;Cvetkoska et al, 2016;Sadori et al, 2016;Zhang et al, 2016).…”

Constant diversification rates of endemic gastropods in ancient Lake Ohrid: ecosystem resilience likely buffers environmental fluctuations

“…Moreover, besides the main core "DEEP", obtained from the deepest part of Lake Ohrid, several other cores were retrieved in shallower parts of Lake Ohrid. The latter appears to be relatively rich in mollusk fossils (see Wagner et al, 2014), which could potentially be used to directly study extinction and speciation events (for a proof of principle see Albrecht et al, 2010).…”