Chlorophyll Fluorescence of Summer Phytoplankton in Reservoirs of the Zvenigorod Biological Station of Moscow State University

Abstract

The results of long-term observations and monitoring of three reservoirs of Zvenigorod Biological Station of Moscow State University using modern chlorophyll fluorescence methods are presented. A sharp increase in chlorophyll content (up to 431 μg/L) and photosynthesis activity (F_V/F_M up to 0.7) associated with the growth of a monoculture, Chlorella vulgaris, was found in 2017 Pozharnyi Pond pond constructed near University dormitory facilities. The high activity of light reactions of this phytoplankton was evident as changes in the following parameters: the maximum quantum yield of primary photochemistry in photosystem II (F_V/F_M), the maximum relative electron transport rate (ETR_max), maximal light utilization coefficient (α), the efficiency of electron transport (φ_Eo) and the performance index of photosystem II (PI_ABS) increased. This was accompanied by a decrease in the density of Q_B-non-reducing centers (V_J) and dissipated energy flux per reaction center (DI₀/RC). The most sensitive parameters of fluorescence induction curve (PI_ABS and φ_Eo) and the coefficient of maximal light utilization coefficient (α) are proposed to monitor the state of phytoplankton in reservoirs.