Dynamics and Relationship between Plankton Organisms in the Littoral Zone of a Large Plain Reservoir at the Beginning of
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mics and Relationship between Plankton Organisms in the Littoral Zone of a Large Plain Reservoir at the Beginning of the Vegetation Season E. V. Kuznetsovaa, *, D. B. Kosolapova, N. G. Kosolapovaa, E. G. Sakharovaa, and A. V. Krylova aPapanin
Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Nekouzskii district, Yaroslavl oblast, 152742 Russia *e-mail: [email protected]
Received February 8, 2019; revised March 25, 2019; accepted March 27, 2019
Abstract—The dynamics and relationship between planktonic algae, bacteria, protozoa, invertebrates, and viruses were studied at different sites in shallow littoral zones of the Rybinsk Reservoir (Upper Volga) in April–June. The features of seasonal succession of different components of the littoral plankton community have been identified. The spring peak in the development of phytoplankton, caused by diatoms and cryptophyte algae, is weakly pronounced in shallow littoral waters. An increase in the number of bacteria and development of protozoa and zooplankton in the littoral occurs earlier than in the open part of the reservoir. Consequently, the clear-water phase starts earlier and has a shorter duration. An important role in the nutrition of the littoral zooplankton, in addition to phytoplankton, is played by heterotrophic protozoa and bacteria developing through the use of both auto- and allochthonous organic substances. Keywords: phytoplankton, zooplankton, microorganisms, littoral, Rybinsk Reservoir DOI: 10.1134/S1995425519060076
INTRODUCTION Phytoplankton play an important role in the structural and functional organization of aquatic ecosystems; its photosynthesis is the energetic base for the existence of all other hydrobionts. The biomass and composition of phytoplankton is regulated by a complex of physical and chemical (light intensity, concentration of nutrients and dissolved oxygen, temperature, and pH) and biotic (grazing and competition) factors, the relative importance of which varies among seasons, years, and water bodies (Vanni and Temte, 1990). Based on the studies of a great number of lakes, reservoirs, and ponds, the plankton ecology group (PEG) model (Sommer et al., 1986, 2012) has been proposed. According to this model, a spring peak is distinguished in the seasonal succession of phytoplankton primarily due to the diatom algae development in water bodies of the temperate geographic zone characterized by the distinct periodicity of climatic, hydrological, and biotic processes. A spring increase in the phytoplankton biomass occurs simultaneously with just as important processes such as water heating and floods, which bring a large amount of allochthonous organic and inorganic matters from the catchment area. This is an important, yet poorly studied, period, which determines, to a larger extent, the plankton dynamics during the year. At the beginning
of summer, the phytoplankton biomass decreases due to grazing by zooplankton (mainly crustaceans), reaching high densities and depletion of nutrients as a result of photosyntheti
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