The phytoplankton of some saline lakes in Central Asia

Abstract

The Aral Sea, Lake Balkhash, and Lake Kamyslybas are closed lakes inCentral Asia. They range from oligosaline to metasaline. The salinity of theAral Sea has increased by more than 30 g L⁻¹ sincewidespread irrigation began in its catchment area. Few studies of thephytoplankton have been conducted on these lakes since extensive irrigationstarted. The investigation reported here compares the flora of phytoplanktonin these saline lakes. In the Small Aral Sea, phytoplankton densitygradually decreased with increasing electrical conductivity (EC) (∼salinity), but there was no such relation in Lake Balkhash and LakeKamyslybas. In the Aral Sea, Dinophyceae and Bacillariophyceae werefrequently observed in most areas of high EC value, and Cyanophyceae weremost conspicuous in the area of medium and lower EC values. In LakeBalkhash, Cyanophyceae were most conspicuous, but Chlorophyceae were alsonoticeable. Most Cyanophyceae in Aral Sea formed filaments with heterocysts.The distinct characteristic of the phytoplankton of the Lake Balkhash wasthat all dominant species form colonies covered with a gelatinous film.Siliceousplankton diversity gradually decreased with increasing EC values inthe Aral Sea and Lake Balkhash.