In 2014-2015 on the West Siberian Plain, fertile populations of 3 species of the genus Spirogyra (section Conjugata) new to this region were found: S. daedalea, S. dictyospora and S. rugulosa. The morphology of the vegetative cells and zygospores of the collected samples is briefly described, the ecological conditions in the habitats are characterized, and photos of Spirogyra daedalea (lateral conjugation), S. dictyospora (ladder-shaped conjugation) and S. rugulosa (ladder-shaped conjugation) are given. In total, in water bodies of the West Siberian Plain the authors found 16 species of the section Conjugata (Spirogyra bellis, S. crassa, S. daedalea, S. decimina, S. dictyospora, S. gracilis, S. hungarica, S. irregularis, S. maxima, S. mirabilis, S. neglecta, S. nitida, S. pellucida, S. rugulosa, S. setiformis, S. varians). Refs 18. Figs 3.

This work summarizes scientific data and the authors’ own materials on about 55 locations of Chara vulgaris in the steppe and forest-steppe belts in the West Siberian Plain. Populations of C. vulgaris have been found in rivers, plain lakes, water reservoirs, ponds, abandoned loops and temporary water bodies in the depth range from 0.1 m to 0.7(2.0) m, on silty sands, rarely on clays. Ecotopes of C. vulgaris comprise fresh and weakly alkalinized waters with mineralization from 0.30 to 4.07 g/ dm 3 with sodium bicarbonate, chloride sodium bicarbonate, chloride calcium bicarbonate and sodium chloride composition. Total hardness is between 2.8 and 37.3 meq/dm 3, pH is 7.2-8.4. The floristic composition of the coenotic complex of C. vulgaris includes 61 species, including 43 species (70.5%) of hydrophilic flowering plants and 18 species (29.5%) of macroscopic algae. A major part in the composition of the agglomerations belongs to flowering helophytes 22 species (36.1%); flowering hydatophytes are represented by 16 species (26.2%), and pleustophytes by 5 species (8.2%). The Chara vulgaris species contributes to temporary communities, pro-coenoses, exhibiting the explerent strategy. The projective cover of C. vulgaris in the agglomerations is usually within 5-10 per cent, more rarely reaching 45-70 per cent. In the Chara vulgaris coenotic complex there were found 1 association (unit of phytocoenosis classification) and 22 ations (unit of pro-coenosis classification) belonging to 17 formations of 3 formation classes and one sub-type of freshwater macrophyte vegetation.

The locality of the two macroscopic algae species is given: Spirogyra majuscule (Zygnematales, Chlorophyta) and Vauchera sessilis (Vaucheriales, Xanthophyta) new to the algal flora of the Republic of Sakha (Yakutia). The information represented is about morphological parameters and ecological-phytocoenotic relations of the found out macroscopic algae species in the investigated hydroecotopes.

In the West Siberian Plain, for a 90-year period Elodea сanadensis has spread initially from the forest-steppe part of the Transurals (the Tobol River basin) mainly along the valleys of large rivers and their feeders as well as in freshwater objects in dividing areas up to Surgut (6'°'9N, 73°24'E) in the north and Ekibastuz (52°0'N, 75°22'E) in the south. The authors have found populations of Е. canadensis in 32 of the 640 studied water bodies (5%), including '4 in Tyumen Region (4 of them in the Khanty-Mansijsk Autonomous District), '2 in Omsk Region, 6 in the northern part of the Republic of Kazakhstan. In the covered territory, the invasion species E. сanadensis exhibits dominating behavior and displaces indigenous species of immersed hydromacrophytes (Ceratophyllum demersum, Myriophyllum spicatum, Potamogeton crispus, P. friesii, Hydrilla verticillata) from the hydroecotopes. The average projective cover by E. сanadensis in the studied West Siberian coenoses is up to 52%. Projective cover by E. сanadensis over 80% has been registered in more than 30% coenoses where this species occurs. In the forest-steppe botanical-geographical belt, coenoses with dominating E. сanadensis form a wetphytomass in the amount up to 3 700-7 336 g/m 2, which is equivalent to 368-690 g/m 2 of air-dry weight. Today, the trend towards further spreading of E. сanadensis across the West Siberian Plain remains.