Application of the phase portrait method for analysis of seasonal dynamics in phytoplankton productivity in a large plain reservoir

Variations in the phytoplankton productivity over the seasonal succession in the Rybinsk Reservoir have been analyzed using the dynamic phase portrait method for years with different hydroclimatic conditions. Stable steady states and critical points in the functioning of phytoplankton, as well as its dynamics as being aberrated from these states, have been revealed and analyzed. It is demonstrated that the seasonal dynamics of the autotrophic community and the rate of its reconstruction depend on hydroclimatic conditions and vary in different parts of the reservoir (reaches). The dynamics of phytoplankton described in terms of the phase portrait method is consistent with the known behavioral patterns of biological systems.