Benthos Algae Communities of Saline Rivers in the Lake Elton Basin: Taxonomic and Quantitative Structure

Abstract

For the first time, an assessment was given of the taxonomic and quantitative structure of the phytobenthos of seven saline rivers in the basin of the hypersaline lake Elton (Volgograd Region). Main types of algacenoses developing on substrates were revealed, namely: diatom phytobenthos, communities of diatoms with cyanoprokaryotes, cyanobacterial films and mats, and epiphyton. The phytobenthos consists of local, mosaic-distributed communities with a small similarity of their species composition. The algacenosis structure is determined by Bacillariophyta (with the predominance of species of the genus Navicula) and Cyanoprokaryota (of the genera Phormidium, Leptolyngbya, and Geitlerinema). The abundance and biomass values vary widely, reaching their highest values (109,834–417,472 mln cells/m2 and 523.6–567.6 g/m2 ) in cyanobacterial communities of mesohaline rivers with their salinity up to 16–19 g/L. Mineralization as a factor influencing the structure of communities, most rigidly acts in the estuarine sections of rivers, by controlling the composition of the dominant species. For critical salinity values (> 70 g/L), characteristic structural transformations of communities by the type of replacement of planktonic and benthic Bacillariophyta and Cyanoprokaryota by planktonic Chlorophyta (of the Dunaliella genus) and picoplankton were established.