Results of research of season dynamics of phytoplankton total numbers and primary production in Uchinskoe reservoir in 1998—2001. Diatom and bluegreen algae play a leading role in seasonal succession of phytoplankton. These groups cause the seasonal number maxima. Spring blooms to be dominated by diatoms (90%) usually found on first ten days of May. Bluegreen algae appear in the phytoplankton in June and their numbers increase very quickly. Bluegreen algae dominate (98%) in phytoplankton till autumn.

Integral estimate of primary production to be made on experimental tests were calculated for seasonal succession periods. Production rates in different region of reservoir were distinguish, but exhibit commonly tendency to annual and seasonal variations. The maximal number seasons were characterized by maximal productivity.