Abundance and distribution of bacterioplankton in the middle and lower reaches of the Ob River in areas impacted by cities
M. Yu. Skopina1, E. V. Kuznetsova1,2, D. B. Kosolapov1,3
1Papanin Institute of Inland Water Biology of the Russian Academy of Sciences, Borok, Russia
2AquaBioSafe Laboratory, Tyumen State University, Tyumen, Russia
3Cherepovetsk State University, Cherepovets, Russia
Keywords: heterotrophic bacterioplankton, size-morphological groups, abundance, biomass, suspended particles, Middle and Lower Ob river
Abstract
Bacteria perform important and diverse functions in the ecosystems of large rivers. The abundance, biomass and spatial distribution of heterotrophic bacterioplankton and its size-morphological groups were studied in the middle and lower reaches of the Ob River in the areas impacted by cities. The river water was characterized by a high content of suspended particles (on average (2.22 ± 0.21) × 106 ml-1), to which a significant part of bacteria was attached: on average, 41.5 % of their total number and 35.7 % of their biomass. The concentration of suspended particles and water conductivity were found to be among the main factors affecting the abundance and structure of bacterioplankton. A significant increase in bacterial abundance, mainly due to small free-living bacteria, was recorded below the mouth of the largest tributary, the Irtysh River, and the city of Khanty-Mansiysk. On this section of the Ob River, the average values of bacterioplankton abundance and biomass were (6.87 ± 4.99) × 106 cells/mL and 142 ± 13 mg C/m3, respectively, which were 1.6-1.7 times higher than in the other sections. The spatial distribution of heterotrophic bacterioplankton in the Ob River is mainly determined by the dynamics of water masses and the influence of tributaries and cities.
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