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The article discusses the features of what is called "hydrobiological succession of flowing waters" in modern scientific literature. These features are associated with the dual nature of such changes: temporal (classical, inherent in a given geographical point) and spatial ("longitudinal") successions (in the latter case, it is more accurate to speak of "clinal" changes—ecoclines, topoclines, etc.). This makes it possible, on one hand, to correct modern knowledge about flowing waters and, on the other hand, to contribute to a better understanding of succession as a general ecological concept. [ABSTRACT FROM AUTHOR]

Depending on the season, the primary production of planktonic communities determined by radiotracer analysis varied within a broad range, from 6 to 314 µg C/(L h). Primary production in cyanobacterial mats was 4.2‒10.9 × 103 µg C/(dm3 h), and Chl a content varied from 6‒13 to 132‒140 mg Chl a/m2. For the plankton, the highest values were revealed in summer (25‒46 mg Chl a/m3), with the maximum in August (223 mg Chl a/m3). High abundance of bacterioplankton (0.3‒7.4 × 106 cells/mL) and massive growth of diatoms (0.15 × 106 cells/mL) with predominance of the genus Chaetoceros were found. Sulfate reduction rates varied from 0.037 µmol S/(dm3 h) in the upper reach to 61.87 µmol S/(dm3 h) in the river mouth. [ABSTRACT FROM AUTHOR]