Content of total free nucleotides in the plankton of the Rybinsk reservoir (Upper Volga)

Abstract

The content of total free nucleotides (TFNs) in the plankton of the Rybinsk reservoir and in specific size fractions of the plankton has been determined by the spectrophotometric method modified by the authors. The content of TFNs amounts to 58.1 ± 5.4, 75.2 ± 4.6, and 64.1 ± 7.3 μg/L in spring, summer, and autumn, respectively, and exhibits a close correlation with the total plankton biomass (r = 0.67), whereas the TFN/Chl parameter is closely correlated to the ratio of autotroph and heterotroph organism biomass (r = 0.96). The contribution of the fraction of more than 3 μm in size (microplankton and nanoplankton) to the TFN pool is 77 ± 4% in spring, 74 ± 3% in summer, and 47 ± 3% in autumn, whereas the contribution of the fraction of 0.45–3 μm in size (ultraplankton) during these seasons is 23 ± 4, 26 ± 3, and 53 ± 3%, respectively. Regression equations that can be used to infer an estimate of plankton biomass from TFN content have been proposed.