Habitat op de overgang van zoet en zout water, Tagangrog Baai (Rusland)

Unique species Black Sea and Caspian Sea in crisis

Naturalis Biodiversity Center
25-JUN-2019 - Drilling in the coastal plains and lagoons on the Black Sea in Romania provides a picture of the evolution of the fauna there. These are unique Pontocaspian species that have evolved in the Black Sea and Caspian Sea areas in the last few million years, such as sturgeons, all kinds of unique lobster species and molluscs, and the Caspian seal (in the Caspian Sea).

The drilling cores have shown that around fifteen Pontocaspian species have flourished in the coastal system over the past few thousand years on the transition of the sweet Danube water and the brackish Black Sea. These species have adapted to specific salt levels.

Some of the unique Pontocaspian species from the bottom of the Razim Lake, including three endemic species of cockle (Monodacna colorata, Adacna fragilis and Hypanis plicatus). Only the first species is still found alive in the last ten years in the Razim Lake systemBut due to the construction of dams that cut off the coastal lakes from the Black Sea and the supply of Danube water through new channels, the system was sweetened. In the last ten years, several species that have been here for tens of thousands of years and possibly much longer are no longer to be found. Of the fifteen species, only three have been found alive. The unique Pontocaspian species are also doing poorly in the nearby coastal zone of Ukraine.

The research, recently published in Biogeosciences, makes it clear that it is essential to restore the natural fresh-salt gradient in the area. For many species, it is unclear whether it is not too late.

Read the article in Biogeosciences (pdf; 12,0 MB).

Text: Naturalis Biodiversity Center
Photos: Frank Wesselingh (leadphoto: habitat on the transition from fresh and salt water, Tagangrog Bay (Russia))