Bacteriobenthos of the suspended sediment in Priplotinny reach of the Kuibyshev reservoir

For the first time, the distribution of the total number and biomass of bacteria, the number of saprophytic bacteria and the size-morphological structure of bacteriobenthos in the suspended sediment of the Priplotinny Reach of the Kuibyshev reservoir were studied. The surface layer of the watered sediment (0.5-1 cm) was studied. The average number of bacteria in the suspended sediment is estimated at 5.19±1.52×109 cells mL-1, biomass - 0.68±0.25 μg mL-1. The average number of saprophytic bacteria is 5.82±0.53×105 CFUmL-1. The size structure is dominated by bacterial cells with linear dimensions of 0.2-0.5 μm and a volume of 0.025-0.100 µm3. The dominant cell morphotype is rods. The percentage of coccobacilli is higher in the littoral, rods - in the profundal. A comparative analysis of bacteriobenthos in the suspended and in the bottom sediments (1-2 cm) was carried out. In the vertical profile, towards the bottom the total number and biomass of bacteria increases, the variability of the dominant size classes of bacteria increases, and by an order of magnitude the percentage of saprophytic bacteria decreases. Spatial distribution of bacteria in suspended sediment conserves the general pattern common for silts - an increase in the number and biomass of cells from upper reaches towards the dam. The exception is the headwater section with increased hydrodynamic activity of bottom waters resulting in decreased quantities of bacteria in the suspended sediment compared to bottom sediment. The largest numbers of saprophytic bacteria on the shallow coast are concentrated in the bottom sediment, in the deep-water central zone of the reach - in the suspended sediment. The distribution of cocci in the upper sediment along the bottom is uniform and does not change with depth. In the bottom sediment cocci reach their greatest quantities in shallow waters, in deep-water biotopes their number decreases.