Species diversity of planktonic and zoobenthic communities of floodplain lakes in the middle reaches of the Irtysh river in the Omsk region

Abstract

Based on hydrobiological studies conducted within the boundaries of the Omsk region, the species diversity of zooplankton and zoobenthic communities of floodplain lakes in the middle reaches of the Irtysh River is presented. The characteristics of zooplanktonic and zoobenthic invertebrates by qualitative and quantitative indicators are considered. The assessment of lakes by trophic and feeding capacity of reservoirs is given. The species diversity of the zooplankton and zoobenthic communities is shown. Zooplankton includes organisms of 20 genera from 11 families. The total number of species is 26, of which 12 are rotifers from two orders belonging to 5 families. Eleven species of branchiform crustaceans belonging to 10 genera from 4 families and three species of copepods belonging to 2 orders. It was found that the greatest species diversity was observed in the lake without the name of the Lubinsky district — 19, the smallest in such lakes as Staritsa, Peschanoe, and without the name of the Tavrichesky district — 12 taxa. The average abundance and biomass for the studied reservoirs was 75.9 thousand copies/m³ and 574.61 mg/m³, respectively. According to the average indicators of zooplankton biomass, floodplain lakes are characterized as ultra-oligotrophic reservoirs of the lowest productivity class. Zoobenthos community of floodplain lakes in the middle reaches of the river the Irtysh of the Omsk region, during the research period, is represented by 25 taxa belonging to three classes of organisms: insects( Insecta), leeches (Hirudinea) and small-scale worms (Oligochaeta). The larvae of chironomids (Sigopominae), mayflies (Ephemeroptera) and small-scale worms (Oligochaeta) formed the basis of the abundance and biomass. The average number of zoobenthos in floodplain lakes of the Omsk region during the study period was 465 specimens/m². The average biomass was 1.519 g/m². According to the average indicators of the biomass of the zoobenthos community, the floodplain lakes of the Omsk region belong to low-feed reservoirs, according to the trophic status — to the oligotrophic type of the low class.