Adaptation of cryomicrobiocenoses to mercury pollution

Abstract

This article presents the results of a layer-by-layer study of the ice thickness in the main channel of the Amur River (Khabarovsk city area) and Pemzenskaya and Amurskaya channels. Spectral and microbiological methods were used to assess the nature of ice contamination with organic compounds. The study of suspensions from ice melts by mass spectrometry (ICP MS) confirmed mercury pollution. Among the cultivated heterotrophic bacteria from the ice mass (cryomicrobiocenoses), there were communities adapted to high mercury concentrations (up to 0.001 mg/L). In some layers of the ice, we recorded a high portion of sulfate-reducing bacteria involved in mercury methylation. In the mainstream of the Amur River, a layer of ice (70-117 cm) had a high content of mercury, dissolved organic matter, plant detritus, and the maximum number of bacteria resistant to mercury pollution. This ice layer was formed during the period of technological discharges from reservoirs to combat the consequences of a major flood in the Amur River Basin. The indicator of resistance of cryomicrobiocenoses to high mercury concentrations was due to the adaptive potential of heterotrophic microorganisms, including active mercury methylators, i.e. sulfate-reducing bacteria. This indicator can be used for a retrospective assessment of mercury pollution of rivers during the freeze-up period.