Abstract:
Microalgae in planktonic communities are the main producers of biomass in lake ecosystems; however, their stability is influenced by many environmental factors. This study aims to
assess the ecological state of Lake Maybalyk, located in Astana (Kazakhstan), based on the study
of the taxonomic diversity and structure of phytoplankton, zooplankton, and the physico-chemical
properties of the water. From 2019 to 2021, samples were taken for phytoplankton analysis, hydrochemical analysis of the water, zooplankton, and saprobiological analysis of the algocenosis. The
study also investigated the main morphometric parameters of the lake, as well as the composition of
hydrobionts, such as zooplankton, zoobenthos, and ichthyofauna. The analysis of phytoplankton
revealed the presence of 97 species and intraspecific taxa of microalgae, with 71 types of microalgal
indicators indicating water saprobity. The planktonic algoflora in Lake Maybalyk is predominantly
composed of diatoms (Bacillariophyta) and green algae (Chlorophyta), which play a vital role in
oxygen production and the food chain within the reservoir. Based on the Pantle–Buck saprobity index
(2.15–2.5), the water quality in Lake Maybalyk is classified as moderately polluted. The assessment
of the water quality, considering the number and composition of indicator phytoplankton species,
places Lake Maybalyk in class III (β-mesosaprobic). The hydrochemical indicators align with the
hydrobiological indicators, confirming the water quality as class III. The trophic status of the reservoir,
during the study period, can be described as average. The obtained data on both the hydrobiological
and hydrochemical indicators correlate, suggesting satisfactory water quality and the ability of the
reservoir to purify itself. This study contributes to the sustainable management of water resources,
by providing essential data on the ecological state of Lake Maybalyk. The results underscore the
importance of continuous biomonitoring, with microalgae as indicators of water quality, which is
crucial for developing effective ecosystem conservation strategies.
