Caspian Sea
The Caspian Sea, like the Black Sea, Namak Lake, and Lake Urmia, is a remnant of the ancient Paratethys Sea. It became landlocked about 5.5 million years ago due to tectonic uplift and a fall in sea level. During warm and dry climatic periods, the landlocked sea almost dried up, depositing evaporitic sediments like halite that were covered by wind-blown deposits and were sealed off as an evaporite sink when cool, wet climates refilled the basin. (Comparable evaporite beds underlie the Mediterranean.) Due to the current inflow of fresh water, the Caspian Sea is a freshwater lake in its northern portions, and is most saline on the Iranian shore, where the catchment basin contributes little flow. Currently, the mean salinity of the Caspian is one third that of Earth's oceans. The Garabogazköl embayment, which dried up when water flow from the main body of the Caspian was blocked in the 1980s but has since been restored, routinely exceeds oceanic salinity by a factor of 10.
Caspian Sea
Many rare and endemic plant species of Russia are associated with the tidal areas of the Volga delta and riparian forests of the Samur River delta. The shoreline is also a unique refuge for plants adapted to the loose sands of the Central Asian Deserts. The principal limiting factors to successful establishment of plant species are hydrological imbalances within the surrounding deltas, water pollution, and various land reclamation activities. The water level change within the Caspian Sea is an indirect reason for which plants may not get established.