Ecological Systems and Devices Annotation << Back THE ROLE OF SIMOCEPHALUS VETULUS IN THE BREAKAGE AND CONSUMPTION OF CYANOBACTERIA MICROCYSTIS AERUGINOSA T.N. Gerasimova, P.I. Pogozhev, A.P. Sadchikov Cyanobacteria Microcystis aeruginosa Kützing dominated in the plankton of a highly trophic pond. The filtering zooplankton was represented by fine species (less than 1 mm in size) with extremely low biomass. Large-size filtering crustaceans were not present because of their grazing by ichthyofauna. The filtering zooplankton, with its low biomass and small size, cannot resist cyanobacteria blooming. In an experimental installation, the isolation of fish facilitated the development of large-size zooplankton species (Simocephalus vetulus O.F. Müller). Juvenile organisms from the water bodies penetrated into the installation where they reached large population and biomass. The size of species reached 1,9…2,1 mm. The abundance of crustaceans increased to 250…480 spec./L. The biomass of S. vetulus in the experimental installation was 320 times higher than the biomass of the planteating zooplankton in the pond. The food base of S. vetulus increased due to the destruction (breakage) of large colonies of cyanobacteria and their transformation into finer fractions consumed by S. vetulus. In this process, the biomass of the fraction with a size larger than 100 μm changed into a fraction with a size edible for S. vetulus. In the late summer, old colonies decomposed into single cells 4 μm in size. The species of S. vetulus create a size fraction acceptable for their further consumption. This contributes to an increase in the food base for the ecosystem. Keywords: zooplankton; cyanobacteria; blooming of water bodies; Simocephalus vetulus; Microcystis aeruginosa; planktoneating fish. DOI: 10.25791/esip.05.2021.1228 Pp. 30-37.