UDC 551.41

Yanina T.A.,  Semikolennykh D.V.,  Sorokin V.M. BIODIVERSITY OF MALACOFAUNA IN THE CASPIAN-MANYCH-PONT SYSTEM DURING THE LAST INTERGLACIAL EPOCH // Arid Ecosystems. 2024. Vol. 30. № 2 (99). P. 119-135. | PDF

The conditions of the biodiversity formation and their comparative analysis at individual stages of development of the Ponto-Caspian basins in the MIS 5 epoch have been identified. The work was carried out based on the results of studying materials from many years of field research in the Caspian, AzovBlack Sea regions and the Manych Depression. The biodiversity of malacofauna in the Caspian-ManychPont system under the climatic conditions of the MIS 5 epoch was closely linked with the basin’s history. Two transgressive basins, Late Khazarian and Hyrcanian, have been reconstructed in the Caspian Sea. The Late Khazarian malacofauna of the northern part of the paleo-Caspian Sea is represented by 26 species. The majority of the Late Khazarian species belongs to the Cardiidae family and are Caspian endemics. The main species is Didacna surachanica Andrusov, 1910. The Hyrcanian malacofauna includes 22 species, the majority of which are also Caspian endemics. The main species are Didacna subcatillus Andrusov, 1910 and Didacna cristata Bogachev, 1932. The malacofauna composition is influenced by factors such as inheritance from the previous basin, aquatic environment’s salinity and temperature, and the introduction of freshwater fauna with river runoff. The significant impact of unexpected catastrophic events, such as the sudden break of a periglacial lake and the subsequent flow of its waters into the Caspian Sea, has led to a sharp change in the biodiversity of the Hyrcanian basin in comparison to the Late Khazarian basin. The Pont’s Karangatian transgression occurred in three stages. In the northeastern part of the Pont, the malacofaunal composition consists of 37 species, mostly Mediterranean species, both
euryhaline and stenohaline. Each stage is characterized by its malacofaunal complex, which includes varying degrees of euryhaline or stenohaline elements. The second complex, corresponding to the maximum stage of transgression, was characterized by the greatest diversity and the presence of the most halophilic elements. An important feature of the third complex is the presence of Caspian species characteristic of the Hyrcanian transgression of the Caspian Sea. The events that occurred in the Manych Depression, which are closely associated with the evolution of the Caspian and the Pont, have been reconstructed: the ingression gulf of the Karangatian transgression of the Pont in the second stage of its development; reduction in the length of the bay, with the simultaneous advance of waters of the Hyrcanian transgression and their discharge into the bay; complete release of the Manych Depression from the Karangatian waters and the discharge of the waters of the Hyrcanian transgression into the Karangatian basin in the third stage of its development. The Pont’s species diversity was determined by the malacofauna composition that migrated from the Mediterranean Sea. At the final stages of the development of the Karangatian transgression its faunal composition was influenced by Caspian invasive species that penetrated the Pont with the waters of the Hyrcanian transgression through the Manych Strait. The composition of malacofauna in the Caspian Sea was primarily the result of evolutionary processes. Migration was the main factor in the formation of the Black Sea malacofauna, without any evolutionary influence.

Keywords: Late Pleistocene, climate change, Late Khazarian transgression, Hyrcanian transgression, Karangatian transgression, species evolution, malacofauna migration.

Acknowledgments. This study was financially supported by the Russian Science Foundation, project No. 22-27-00164 (2022-2023) “Environmental evolution of the Ponto-Caspia region during the last interglacial epoch”.

Funding. The study was carried out with support of the Russian Science Foundation project No. 22-27-00164 (2022-2023) «Evolution of the natural environment of the Ponto-Caspian Sea in conditions of the last interglacial epoch».

DOI: 10.24412/1993-3916-2024-2-119-135
EDN: NVDSVE