Participation of microorganisms in the balance of high-molecular organic compounds in the highly productive system of the Chernavka salt river (Prieltonya region)

In the shallow Chernavka River, which flows into the self-sedimentary Lake Elton, the intensity of primary production of phototrophic communities was determined: planktonic – from 0.025 to 0.256 mg C / l ∙ h, benthic – from 9.6 to 12.5 mg C / dm3 ∙ h, algal planktonic and cyanobacterial mats – from 4.6 to 8.76 mg C / dm3 ∙ h. The intensity of dark assimilation of carbon dioxide in water varied from 14 to 31.8 mg C / l ∙ day, and in sediments from 2.6 to 69 mg C / dm3 ∙ day, indicating a high variability of heterotrophic processes. High concentrations of organic compounds were found in surface waters, which for lipids, aliphatic hydrocarbons and polycyclic aromatic hydrocarbons averaged 692, 80 and 0.79 μg/l, respectively. The composition of aliphatic hydrocarbons in sediments was characterized by the presence of planktonic low-molecular homologues n-C15–C17 and a sharp increase in the series of odd high-molecular alkanes, and the composition of polycyclic aromatic hydrocarbons was characterized by an increase in the proportion of naphthalene. The resulting bottom sediment library was dominated by 16S rRNA gene sequences belonging to the phyla Pseudomonadota (69.09%), Bacteroidota (11.64%) and Chloroflexota (7.92%).