Zooplankton of Pronskoye reservoir in August 2023

Abstract

The aim of this study was to investigate the zooplankton of Pronskoye Reservoir during the summer period of 2023. Sampling and processing of hydrobiological zooplankton samples were carried out using standard methods in August 2023 at six monitoring stations in Pronskoye Reservoir. A total of 15 zooplankton taxa were identified in the samples: 6 taxa of rotifers, 5 taxa of cladocerans, and 4 taxa of copepods. On average, the abundance and biomass of zooplankton (mean values across stations) in Pronskoye Reservoir in August 2023 were 928.1 thousand individuals/m3 and 3.4 g/m3, respectively. Rotifers dominated in terms of abundance (63,5%), while cladocerans dominated in terms of biomass (40,3%). Pronskoye Reservoir exhibited above-average productivity in terms of zooplankton, which is favorable from a fisheries perspective. The abundance and biomass of zooplankton for all major groups (rotifers, cladocerans, and copepods) were higher in the lower part of the reservoir, separated from the middle and upper parts by a narrow neck. The increase in the abundance of the rotifer species Brachionus angularis was particularly noticeable in the lower part of the reservoir. The lower part of the water body is classified as highly productive, while the middle and upper parts has above-average productivity. The lower part of the reservoir is characterized by lower temperatures and lower dissolved oxygen concentrations in the water. The lower part of Pronskoye Reservoir exhibits a more diverse species composition compared to the middle and upper parts. It is evident that abiotic factors, in one way or another, determine the differences in the abundance, biomass, and species composition of zooplankton between the lower and upper parts of Pronskoye Reservoir.