In mountain regions, biological soil crusts (BSCs) provide essential ecological services by being involved in primary production and nitrogen fixation. Eukaryotic algae and cyanobacteria are important photosynthetic components of these unique cryptogamic communities. Here, we present an overview of the eukaryotic and prokaryotic diversity of such phototrophs in BSCs in the mountain tundra of the northern Ural Mountains. Such assessment is based on morphological surveys and the first metabarcoding analysis in the region. In total, 166 taxa of Cyanobacteria and 256 eukaryotic algae (including Euglenophyta, Ochrophyta, Dinophyta, Bacillariophyta, Chlorophyta, and Charophyta) were identified. For the first time, 86 taxa new to the BSCs of the high-mountain belt of the region were discovered. Considering species composition, Cyanobacteria and Chlorophyta are the most abundant taxa in all the analyzed BSCs. The genera Nostoc, Coccomyxa, Chlamydomonas, Leptolyngbya, Stenomitos, Pycnacronema, Stigonema, and Eunotia had the highest number of taxonomic units. These groups shape the structure, function, and ecology of the BSC communities in the studied region. Our results show that BSCs in the tundras of the Ural Mountains have a high active and passive biodiversity of terrestrial cyanobacteria and algae. Both implemented methods resulted in similar results with a comparable number of algae and cyanobacteria species per sample. Metabarcoding could be implemented in future in the region to accurately screen photosynthetic organisms in BSCs.

We studied how ecological factors affect species composition and structure of soil algal assemblages in different types of mountain tundra and sparse forests in the Northern Urals. Soil moisture, pH, nitrogen content and amount of solar radiation were determined using Ellenberg indicator values from phytoindicators. Species identification of soil algae was made using light microscopy following algal culture. We identified 74 algal species from five divisions. Most species were Cyanobacteria and Chlorophyta. For each habitat type we identified species with high frequency and fidelity. Algal species diversity was maximal in herbaceous plant communities, minimal in lichen communities, and showed a positive correlation with soil moisture and nitrogen content.

The literature and original data on the species diversity of soil algae in the Northeastern European Russia are summarized. The table of 692 species belonging to 242 genera, six divisions with data on their distribution, known ecological and phytogeographical characteristics is presented. The most studied areas of this territory in soil algae are the Bolshezemelskaya tundra (Vorkuta tundra) where 251 species were identified, the Pechora lowland (Voseiskoye deposit) — 205 species, and the mountain tundra of the Subpolar Urals (the Kozhym River Basin) — 206 species. Taxonomic and ecological-geographical analyses of the flora of soil algae of the Northeastern European Russia are provided.

We describe the morphological features and the phylogenetic relationships of five morphologically similar strains belonging to the genus Coelastrella, which live in different ecological and geographical conditions of terrestrial ecosystems: in the Ural Mountains (Polar, Subpolar, and Northern Urals of Russia) and the Khentii Mountains (Russia and Mongolia). We analysed algal strains stored in the Culture Collection of Algae of the Institute of Biology, Syktyvkar, Russia (SYKOA Ch-045-09, SYKOA Ch-047-11, SYKOA Ch-072-17) and the Culture Collection of Algae at Herbarium of the Siberian Institute of Plant Physiology and Biochemistry, Irkutsk, Russia (IRK-A 2, IRK-A 173). By light microscopy, all samples were assigned to Coelastrella terrestris. However, the phylogenetic analyses based on the nucleotide sequences of 18S rDNA and ITS1-ITS2 showed that only one strain belongs to C. terrestris (IRK-A 173). Other samples were closer to C. oocystiformis (SYKOA Ch-045-09; IRK-A 2) and C. aeroterrestrica (SYKOA Ch-047-11). The strain SYKOA Ch-072-17 is probably a new species for the genus. These results confirmed the high phenotypic variability and the hidden diversity among the members of this green algal group.

The influence of edaphic and orographic factors on the formation of algal diversity in biological soil crusts was studied in mountain tundras of the Polar and Subpolar Urals. Bare spots developed in...