Scientific publications

The study of zooplankton is important for understanding the functioning of lake ecosystems, assessing biodiversity, and solving practical problems related to fish farming, environmental monitoring, and water resource protection. The aim of this study was to analyze the influence of summer stratification and spring homothermy on the composition of zooplankton in Lake Dolgoe, its quantitative development and vertical distribution. In spring and summer, the numbers of species in the pelagic zooplankton community of Lake Dolgoe were similar (21 and 22 species, respectively). While the species richness was almost identical, crustaceans were more abundant in summer (59.1 %), while in spring, rotifers accounted for 66.7 % of the species composition. These changes in the species composition were due to the absence of thermophilic cladocerans. In July, Kellicottia longispina (Kellicott, 1879) was the only rotifer in the dominant assemblage, accounting for 18.8 %. The most abundant cladocerans were Diaphanosoma brachyurum (Lievin, 1848) with 7.7 % and Daphnia cucullata Sars, 1862 with 5.9 %. In March, the cold water rotifer Synchaeta cecilia Rousselet, 1902 accounted for more than half (58.2 %) of the total population. The relict cold-water rotifer Limnocalanus macrurus G. O. Sars, 1863, which breeds during the winter season, was represented by all developmental stages and constituted 24.4 % of the total population. The total zooplankton abundance was twice as high in summer as in spring. This decrease was primarily due to a decrease in the abundance of cladocerans. The vertical distribution of the zooplankton community varied seasonally. Overall, the concentration of organisms remained the highest in the upper water layers throughout both seasons, but the abundance in the surface water layers in summer reached 50 % of the total population, compared to only 25 % in spring. These differences are due to changes in the species composition, distribution patterns of the main groups, and changes in the dominant assemblage.