Conservation palaeobiology in the Razim-Sinoie lake complex (Romania): how sedimentology and mollusc reconstruction can be used for conservation strategies.

Conservation palaeobiology uses fossil data and time series to make informed contributions about conservation strategies of endangered species. When studying variation, time series often lack the current human-caused impact on ecosystems, while the rate of change has increased substantially in the past century. The unique endemic fauna in the Caspian Sea and the Black Sea have evolved under strongly fluctuating salinities, and experienced episodes of connection and isolation between the two basins and with the world’s oceans. This so-called Pontocaspian fauna that has adapted to these unique brackish environments, is currently facing a biodiversity crisis. The Razim-Sinoie lake complex, located on the Black Sea coast, is still hosting Pontocaspian fauna until today. Although it is considered prime Pontocaspian habitat, the modern ecosystem is dominated by fresh water species. Eleven sediment cores were used to document variations in the mollusc assemblages through space and time. The sediment facies in the same cores represent the depositional history of the lake. Results show a dynamic system where riverine and marine processes alternate. Fresh, marine and Pontocaspian mollusc communities are distributed in space and shift through time. The current decline in Pontocaspian species is observed in the top layers. This might be related to the anthropogenic adjustments to the system since the 20th century, as the complex has been actively transformed from a semi-open marine-freshwater system to a fresh-water lagoon. Our research considers the restoration of salinity gradient to preserve Pontocaspian species in the future. This research is carried out as part of the PRIDE project – this project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 642973.