Ecotonic Communities of Diatoms in the Southeastern Part of the Kamchatka Peninsula

Data about the ecotonic diatom communities of the Kamchatka Peninsula, a unique territory with strong volcanic activity, are very limited. We aimed to investigate diatom algae of the ecotones in the southeastern part of Kamchatka, including the Paratunka river valley, at the foot of the Vachkazhets volcano, and the bank of the Bystraya river. In total, 55 taxa were identified. The most diverse were the flora of the Paratunka river, with 31 taxa. Near the Bystraya river, 26 taxa were identified. Near the Vachkazhets volcano, 18 taxa were identified. Fragilariforma virescens, Planothidium lanceolatum, Pinnularia cf. subcapitata, Halamphora normanii, Nitzschia palea, and Eunotia exigua were the dominant species in the studied ecosystems, with the maximum abundance score. Pinnularia cf. subcapitata and Planothidium lanceolatum were found in all ecotones. In the studied habitats, small indifferent alkaliphilic cosmopolitan species prevailed. Our study revealed that the diatom species composition of the Kamchatka ecotones reflects their adaptability to survive in the extreme conditions of volcanic substrates. The results contribute to our knowledge of the ecology and biogeography of a number of diatom taxa.