Distribution of bacteriobenthos along the riverbed and coastal profiles of the Votkinsk reservoir

The results of a study of the spatial distribution of bacteriobenthos in the Votkinsk reservoir are presented. The estimation of the abundance and biomass of bacteria, the size-morphological structure is given, the features of the spatial distribution of bacteriobenthos in the riverbed and coastal profile of the bottom bed are revealed. The latitudinal zonality, hydrological-morphological and morphometric features of the Votkinsk reservoir determine the main patterns of distribution of bottom sediments and bacteriobenthos in the reservoir. In accordance with hydrological criteria, two areas of formation of different types of bottom sediments have been identified: sands and sandy silts from the Kama hydroelectric power station dam to the Osa station, and fine silts from the Osa station to the Votkinsk hydroelectric power station dam. Factors influencing the spatial distribution of bacteriobenthos were identified: hydrological, morphological and morphometric features of the reservoir, types of bottom sediments, particle size distribution, organic matter content in the bottom sediments. Two opposite trends were identified in the spatial distribution of bacteria along the bottom bed: 1 - an increase in the abundance of bacteria along the riverbed profile from the upper reaches of the reservoir to the lower section, 2 - a decrease in the abundance of bacteria along the coastal profile in this direction. In accordance with the hydrological and morphological zoning, three sections are identified in the distribution of bacteria in the channel profile: I - upper section with the minimum number of bacteria, II - central: a gradient of increasing bacterial numbers, III - lower section with the highest number of bacteria. The trend in the abundance of bacteria in the riverbed profile was characterized by a sawtooth character and lower values of quantitative characteristics of the bacteriobenthos. The total abundance of bacteriobenthos varied from 0.8×109 to 4.1×109 cells mL-1, biomass - from 36 to 580 μg mL-1. In sands, the abundance and biomass of bacteria is lower (N = 2.0±0.1×109 cells mL-1, B = 144±22 μg mL-1) compared to silts (N = 3.1±0.19×109 cells mL-1, B = 276±34 mg/kg).