Cyanobacteria (formerly blue-green algae) are unique primary producers of aquatic and terrestrial ecosystems capable of oxygenic photosynthesis. Many studied species of cyanobacteria are cosmopolitan and are widely used as objects for biotechnological needs and scientific research. In addition, there are endemic and rare species of microalgae occupying special ecological niches. For example, unicellular asymmetrically dividing cyanobacteria of the family
Chamaesiphonaceae. They lead an attached lifestyle and occur as epiphytes of aquatic plants or inhabit rock surfaces of streams and fast-flowing rivers. They belong to the oligosaprobic microorganisms — dwellers of very clear waters,
preferring low organic matter content. Some known species of Chamaesiphon are reliable bioindicators of water purity status and, according to the previously approved European Water Directive 2000/60/EC, they are used to monitor
the state of natural ecosystems (Gutowski et al., 2015). In connection with the expansion of human economic activity and the constant increase in anthropogenic load, the problems of protection of rare species of water bodies of protected areas of the Russia, as well as the description of their biodiversity, are becoming more urgent.