The Caspian Lake: History, biota, structure, and function

Abstract

The elongate, endorheic Caspian Lake has a north-south orientation and its main freshwater inflow, the Volga River, enters at the shallow north end. Two deep basins occupy its central and southern regions. These facts lead to horizontal differences in temperature, salinity, and ecology. Nutrient levels and primary production are low. Historically, lake level has fluctuated by -6 m, but on the geological timescale, fluctuations of >200 m have occurred. The lake formed in the late Miocene, first went through a long shrinking phase, expanded to three times its present size in the late Pliocene, and repeatedly rose and fell throughout the Pleistocene, with corresponding freshenings and salinizations. The lake surface has remained below sea level since the last pleniglacial. This dynamic history led to the assemblage of a set of euryhaline biota of Tethyan and freshwater origin, besides Baltic elements, that invaded with glacial meltwater. Endemism is as high as in Lake Baikal, but typical marine groups are absent. Because the lake is oxygenated to the bottom, its biota show a vertical zonation, but without a true abyssal community, suggesting cat&&ophic episodes of deep anoxia.

New organic-walled dinoflagellate cysts from recent sediments of Central Asian seas

“…In Fig. 2A, sea-ice limit is indicated (dotted line) and mixing in the water column is shown with, in zone 1, a mixing from bottom to surface waters, and in zone 2, a gradient of mixing with increased depth, from south to north (after Kosarev and Yablonskaya, 1994;Dumont, 1998). (Fensome et al, 1993).…”

“…In the Middle Pliocene, orogenic activity separated the southern part of the Caspian Sea from the Black Sea but later they were temporarily reconnected, where the Caspian Sea was part of a slightly salty Pontic lake. The Caspian Sea was connected to the Aral Sea during the Pliocene and Pleistocene as the result of major transgressions linked to large-scale influx of melt water from high latitude ice caps (Dumont, 1998;Grosswald, 1980Grosswald, , 1993Mamedov, 1997). For the last 300 ka, the Caspian Sea has existed as an isolated water body (Boomer et al, 2000), awith some short transgressive episods associated with interglacial periods and global sea-level changes (Svitoch et al, 2000).…”

“…Dumont, 1998) with modern assemblages derived from three sources: the Mediterranean Sea, the Arctic, and river input. The Caspian Sea biota ranges from freshwater to brackish to euryhaline and has a low diversity.…”

River inflow and salinity changes in the Caspian Sea during the last 5500 years

“…Dumont, 1998;Grigorovich et al, 2003;Marret et al, 2004). The CS biota ranges from freshwater to brackish and to euryhaline types, with species of freshwater origin tolerating salinities up to 13 and species of marine origin tolerant of salinities down to 13 (Dumont, 1998).…”

Essentials of Endorheic Basins and Lakes: A Review in the Context of Current and Future Water Resource Management and Mitigation Activities in Central Asia

“…The Caspian Sea is the largest inland water body in the world with a vast drainage basin of about 3 million km 2 , covering almost 2% of the world's territory [39,40]. The Caspian Sea ( Figure 2, sector 4) is situated on a virtual border between Europe and Asia, surrounded by the territories of Russia, Azerbaijan, Iran and Turkmenistan [40].…”