Современное состояние зоопланктона Малого Моря оз. Байкал (по данным 2022 г.)

Abstract

Original results of studies of zooplankton in the Maloe More Strait of Lake Baikal in 2022 are presented. Changes in species composition, quantitative indicators of development and the structure of zooplankton in years of different water levels are analyzed. Zooplankton was collected on 5 transects in three depth zones: central about 200 m, coastal – about 10 m, shallow – less than 1 m. At deep-water stations, zooplankton includes 5 species of Rotifera and Cladocera, 2 species of Copepoda and 1 species of Amphipoda. Epischura baikalensis and Cyclops kolensis formed the basis (up to 99% of the total number) of the total population density (up to 2100 ind./m3 ) and biomass (up to 140 mg/m3). Macrohectopus branickii may also constitute a significant portion of the biomass at some stations. Coastal zooplankton is characterized by an increase in taxonomic diversity to 28 species, of which 79% are Rotifera. The population density increases to 115 thousand ind./m3 and biomass to 492 mg/m3, but the structure of zooplankton does not change due to the preservation of the dominant complex of Copepoda. A fundamentally different planktocenosis is formed at shallowwater stations, the taxonomic composition of which includes the same species as in deeper-water zones. However, non-endemic rotifers Synchaeta spp., Keratella cochlearis tecta, Polyarthra dolichoptera and others, which together make up more than 96% of the total number, become systemforming species. Of the endemic species, only the meiobenthic phytophilic crustaceans Chydorus baicalensis and Alona setosocaudata, as well as the rotifers Euchlanis ligulata, Dicranophorus sp., play some role. Zooplankton in the shallow water zone is characterized by a high abundance of up to 425 thousand ind./m3, however, taking into account the dominance of small-sized rotifers, a relatively low biomass – up to a maximum of 154.9 mg/m3. The structure and density of the population of plankton in the deep-water and coastal zones of the transects shows similarity with the zooplankton of the average water level in 2012. The taxonomic composition and quantitative characteristics of the shallow zone correspond to the zooplankton of the most warmed bays of the Maloe More Strait.