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There is analysis of the taxonomic diversity of Rotifers, Copepods, and Cladocerans from water bodies, located on the territory of clusters of the Ubsunurskaya Kotlovina State Natural Biosphere Reserve, located within the Russian part of the Ubsunur Basin, on the border with Mongolia. A total of 87 species from 53 genera, 22 families, 10 orders were recorded. Cladocerans include 40%, Copepods – 37% and Rotifers – 23%. The dependence of species diversity on the level of mineralization was established – 89% were found in fresh water bodies, in salty – 23%, in brackish – 14%. Zooplankton composition of the Lake Tore-Khol has undergone some changes in comparison with the data of the second half of the last century. The zooplankton contains species of crustaceans that are rare for the Rossian fauna – Apocyclops dengizicus, Eucyclops dumonti, Alona flossneri. Tuva is the northernmost point of A. dengizicus in Russia – its habitat, lake Amdaigyn-Khol, located at 530 parallel. The spring Bulak is polluted by mechanized water intake for technical needs, which is confirmed by the appearance of an indicator of this process – Brachionus nilsoni, which then enters the lake Shara-Nur. Location on the shore of the lake Tore-Khol camp site led to the development of Filinia longiseta, which had not previously been observed in large numbers. In general, the presence of rare species for the fauna of Russia in the water bodies of the reserve indicates the presence of favorable conditions for their development and life.

The species composition of zooplankton in mineralized water bodies located in the Ulug-Khem basin (Republic of Tuva) was studied. These lakes have the status of natural monuments of regional significance. In total we recorded 53 species of microscopic Custaceans and Rotifers from 32 genera, 13 families, and 8 orders. Cladocera comprises 53% of the species. The dependence of the species diversity on the level of mineralization was revealed; 89% of the species were found in brackish water bodies. The zooplankton composition of the hyperhaline lakes Dus-Khol (Svatikovo) and Cheder has remained constant for many dozen years. The zooplankton includes some species known only from Republic of Tuva in Russia, namely, Microcyclops afganicus and Macrotrix tabrizensis. M. asiaticus and Alona irinae, rare for the fauna of Russia, live in the lake Haak-Hol. A decrease in the total numbers of zooplankton is observed in the lakes, namely: in the lake Dus-Khol, it has decreased by 4 times, in the lake Khadyn it has decreased by 10–19 times as compared to the middle of the last century. Despite the lack of intermediate information, we regard this as a consequence of anthropogenic impact. The emergence of an indicator of pollution (Brachionus nilsoni) in the lake Khadin confirms this version. At the same time, the stable finding of species rare for the fauna of Russia indicates the presence of favorable conditions for their development and life, which increases the value of the reservoirs themselves, which are already unique natural objects.

The article provides information on the species composition and quantitative indicators of zooplankton in two small mountain reservoirs of the Tuva Republic: the Eerbek and Turan. They reflect the first and the third years of the ecosystem existence after seasonal drawdown. Regulation shows a typical pattern in the distribution of zooplankton in the reservoirs: an increase in density in the dam section. In general, the reservoir zooplankton has a floodplain type of formation. The existence periods of reservoirs influences the zooplankton structure and its development: regulation in the first year determines the development of crustacean zooplankton (represented mainly by cladocerans), usually with monodominance; over three years, all main groups of zooplankton develop, but drawdowns interrupt the formation on the normal ecosystem in the reservoir.

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