Microbiological transformations of mercury species in aquatic environments

Biogeochemical cycle of mercury (Hg) is a complicated series of biotic and abiotic reactions, from which formation of monomethylmercury (MeHg) is widely considered as the most important, due to the proven toxicity of MeHg [1]. Organomercury forms have a pronounced capability of bioaccumulation (incorporation in cells and tissues of living organisms) and biomagnification (transport through trophic levels) [1]. In order to understand how the MeHg enters food resources, transformation of mercury and its species in the aquatic environment needs to be understood. Microorganisms play a fundamental role in mercury transformation processes (reduction, oxidation, methylation, demethylation). Hg transport and transformations are also governed by the physical and chemical properties that characterize the aquatic environment (pH, redox potential, temperature, salinity, dissolved oxygen, presence of dissolved organic matter, etc...). The objective of this research is to better understand the role of microorganisms in mercury cycling in typical Slovenian surface water bodies as a response to mercury loads from air and water born sources. The work plan involves the following steps: (i) acquisition of measurement data on mercury analysis and speciation in precipitation and surface waters; (ii) use of chemical analytical methods for mercury analysis and speciation and transformation processes using radiotracers; (iii) application of microbiological and molecular tools to understand the role and response of microbial population to mercury stress.