To ecology and morphology of Thalassiosira incerta Makarova (Bacillariophyta)

Thalassiosira incerta has reached an appreciable level of quantitative development in the Cheboksary Reservoir and Oka River (hundreds of thousands and millions of cells per liter, from tenths to tens of grams per cubic meter). Higher abundance and biomass of this species are recorded during the low-water period (August). Algal bloom, to the extent typical for eutrophic/hypertrophic waters, is observed in the Oka River in its section with a typical river regime which is not subjected to the reservoir’s backwater effect. Our studies make it possible to specify the ecology, range, and morphological features of the species. River conditions of highly trophic and highly saprobic water courses during dry years of the vegetation period are optimal for species development.