Seasonal Dynamics of Microbial Processes in Bottom Sediments of the Sevastopol Coastal Area
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A seasonal study of microbial methane oxidation (MO) and sulfate reduction (SR) processes in bottom sediments was carried out at five stations in the estuarian Sevastopol coastal area, which differed in their sedimentation and geochemical conditions. High methane concentrations in bottom sediments, as well as accordingly high MO rates, were obtained at stations marked by high organic carbon (Corg) concentrations. The dependence of these values was found to be exponential, whereas for SR, the amount of organic carbon was not the limiting factor. For the studied stations, the integral SR rates ranged from 2.9 to 11.3 mmol m–2 day–1. The trends of the SR rate have opposite directions for the open and closed parts of the sea: SR decreased during study period at the center of the bay, while in the open sea area it increased. The MO rates varied in a wide range from 0.0001 to 3.6 mmol m–2 day–1; the highest were obtained in Corg-rich sediments of the central part of the bay. Only at one station, where the mean annual Corg content in sediments reached 3.39%, did the methane concentration in sediment pore water exceed the calculated solubility.
The authors thank E.E. Zakharov of the Winogradsky Institute of Microbiology, Biotechnology Research Center, Russian Academy of Sciences, for radioisotope measurements of the SR and MO rates.
The study was supported by the government assignment for the A.O. Kovalevsky Institute of Marine Biological Research of RAS entitled “Molismological and biogeochemical fundamentals of marine ecosystems homeostasis” no. АААА-А18-118020890090-2 as well as by the Russian Foundation for Basic Research within the project no. 16-35-00396 mol_a. The measurements was carried out using the equipment of the Shared Resource Center “New Materials and Resource Conservation Technology” (NNSU).
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