Diversity and ecological characteristic of algae and cyanobacteria of thermokarst lakes in Yakutia (northeastern Russia)

A total of 437 species (453 with infraspecific taxa) of algae and Cyanobacteria were identified in 2034 samples collected during the first research on nine thermokarst lakes in Yakutia carried out in 1986–1994 and 2001–2015. The richest algal flora was determined in Lake Aalah, represented by 241 taxa. Bacillariophyta species dominated in four lakes, whereas Chlorophyta and Cyanobacteria dominated in the others. The algal bioindication demonstrated preferences for benthic and plankticbenthic life, temperate temperature, low alkalinity, waters with moderate oxygenation, low to medium enrichment with chloride, low organic pollution, and mesotrophic state. Comparative floristic, CANOCO and JASP statistical methods divided the species and environmental variables into groups of lakes related to landscape terraces. Local landscape positions and high summer water temperatures may play a major role in the formation of algal flora. The index of algae taxa per area stabilized at about 70 species per km 2 . The highest polymorphism of algae floras, defined by the Subspecies/Species Index, was determined for the lakes of the Tungulunskaya terrace: Lake Ynakh, Lake Nal Tungulu and Lake Tungulu (1.041–1.058), and the average total flora was 1.036. Our results can help in monitoring and protecting the ecosystems of thermokarst lakes in Yakutia in the harsh climate environment of Northeastern Eurasia.