In studying the zooperiphyton of reservoirs and watercourses in the Subarctic of Western Siberia, freshwater sponges were identified. This research was carried out in areas of the southern tundra and forested tundra belts, which in turn were conditionally divided into three zones: western, central, and eastern. In total, this study covered 40 reservoirs and watercourses. Three species of sponges were found: Spongilla lacustris, Ephydatia muelleri, and Ephydatia fluviatilis. The most common species is S. lacustris, E. muelleri being less common compared to E. fluviatilis, which occurs only occasionally. The maximum numbers of species and their occurrence were noted in forested tundra water bodies. Linear measurements and a dimensional analysis of both gemmules and elements of the skeleton of the sponges were carried out. A tendency toward a decrease in size of the skeletal structures of the studied biological material in comparison with the literature data was revealed.

In August - October 2021, mollusks of one of the most active and widely spread alien species on a global scale, (Pallas, 1771), were found for the first time in the Pyshma River on the territory of the West Siberian Plain. The first find in Siberia was made in a watercourse with a natural thermal regime and contained individuals of different size and age groups, which could be an indirect evidence of successful naturalization of the species.

Data on the taxonomic composition of freshwater sponges and bryozoans in the cooling pond of CHPP-1 (Tyumen), as well as data on their distribution in the water area at five stations in 2005, 2016, and 2017, are given. The seasonal development of colonial invertebrates, as well as the influence of high temperatures on the occurrence and biomass of sponges, are considered. It is shown that the most favorable living conditions are formed in lotic biotopes. The size characteristics of gemmules and spicules of sponge Eunapius fragilis (Leidy.) and flotoblasts of bryozoans Plumatella emarginata (Allman.) and Hyalinella punctata (Hancock) are given.

Data on the taxonomic and community composition of zooperiphyton of forest-tundra lakes are presented. The taxonomic composition includes 120 lowest identified taxa (LIT), and the group of insects has the greatest diversity. Eight types of communities are identified, seven of which are found in floodplain lakes and five in nonfloodplain lakes. The most common communities are dominated by chironomid larvae. The maximal biomass is recorded in a community dominated by colonial invertebrates-bryozoans and sponges-which serve as determinants of the consortia.

Dynamics of the development of the invasive crustacean Stenocypris sp. (Ostracoda) was studied in different sections of the cooling pond of the Tyumen Thermal Power Station-1 − in the place of heated water release with the maximal temperature of water and in the zone with moderate heating. It has been found that the type of substrate did not influence the development of Ostracoda. The study of the dynamics of Stenocypris sp. development in periphyton in summer and autumn 2016 has shown that the increased water temperature (to 39.4°C) favored its development, which was accompanied by the increase in the quantitative indices of this species. It has been found that current velocity did not limit the development of this species of Ostracoda.