[Seasonal dynamics of chrysophyte stomatocyst formation in the plankton of Southern Baikal].

The results of studies on the phytoplankton of Southern Baikal in 2004 show that siliceous stomatocysts (cysts) of chrysophyte algae make a significant contribution to this community. Their abundance reaches a peak of 46 800 cysts/l between August and October, when the concentration of biogenic elements is minimum. The D/C coefficient (the ratio of diatom cells to cysts) varies during the year, reflecting the seasonal succession of phytoplankton and changes in the concentration of biogenic elements in the photic layer. Fifty morphotypes of the cysts have been distinguished and divided into 25 groups by morphological characters. These groups differ in seasonal dynamics. The cysts of group 5 (with spines of different lengths in the equatorial and posterior areas) dominate over other morphotypes and reach the highest concentration (13,600 cysts/l) in August. The data obtained in this study may provide an additional criterion for assessing the present-day state of Lake Baikal and for paleolimnological reconstructions.