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Diatoms in epixylon of waters in the European North (Komi republic, NAO)

The results of studying the diatoms in epixylon of 15 water objects in European Northeast of Russia are presented. The samples of nature biofilms from external surfaces of submersed branches of Betula nana, Salix spp., woody snags, and wood debris were investigated. A comparative analysis of diatoms in fouling of woody substrates was carried out from coal-mine settling pond, lakes, streams, and different parts of mountain river. These are in the basins of Ortina, Vorcuta, More-Yu, Vychegda, Izhgma, Shchugor rivers. In stagnant waters diversity of diatoms form 9–56, in waterways 10–102 taxa. Encyonema minutum (Hilse) Mann, Navicula radiosa Kützing, Tabellaria flocculosa (Roth) Kützing were most frequently. A small degree of diatoms similarity in epixylon with other communities was revealed; the Sørensen coefficient is 0,3–0,4. Part of the diatoms with an abundance 3–6 points (28 taxa) were found only in one water bodies. Among them, in thermokarst lakes with low salinity water and a weakly acid reaction halophobic, acidophilic Eunotia microcephala Krasske, Kobayasiella subtilissima (Cleve) Lange-Bertalot, and Cymbella borealis Cleve prevail. In the coal–mine settling pond dominating group is represented by the alkaliphilic, halophilic Diatoma tenuis C. Agardh, Nitzschia clausii Hantzsch, and Gomphonema productum (Grunow) Lange-Bertot et Reichardt. Mountain streams are distinguished by the development of rheophilic Meridion circulare (Grѐville) C. Agardh, Diatoma mesodon (Ehrenberg) Kützing, Encyonema reichardtii (Krammer) Mann, Fragilaria gracilis Oestrup, Fragilariforma virescens (Ralfs) Williams et Round, Gomphonema montanum (Schumann) Grunow, G. pumilum (Grunow) Reichardt et Lange-Bertalot, G. ventricosum Gregory, Hannaea arcus (Ehrenberg) Patrick var. arcus et f. recta (Cleve) Foged. The composition of the epixylon dominant complexes also differs depending on the hydrological conditions and characteristics of aquatic environment. These differences in this community determine the significant diversity of this group of algae as a whole. In total, 244 species with intraspecific taxa from 67 genera and 27 families identified, and a large number of rare species found.