Metazooplankton of the plain reservoir during climate warming: Biomass and production

Abstract

The structure and dynamics of biomass and production of various trophic groups of metazooplankton in the Rybinsk Reservoir before climate warming (until 1977) and during the warming period have been analyzed on the basis of long-term (1956–2010) observations. In 2004–2010, the values of biomass (0.9 g/m3) and production (54 kcal/m2) in the reservoir pelagial were lower than at the peak of metazooplankton development in the 1980s–1990s (1.2 g/m3 and 73 kcal/m 2, respectively). However, the former values were higher by a factor of 1.5 (0.6 g/m3 and 37 kcal/m2, respectively) than before climate warming. As of recently, the productivity of metazooplankton in the reservoir corresponds to the level of eutrophic waterbodies. As a result of warming, the duration of the period of mass development of summer zooplankton has increased for about 2 weeks, and the maxima of biomass and production are registered in the second half of summer (August). The efficiency of the energy transfer from the phytivorous to predatory plankton and the rate of the matter cycling in zooplankton of large plain reservoirs in relation to changes in the trophic status of their ecosystems under climate warming are discussed.