Potential for mercury reduction by microbes in the high arctic

Area of Science:

• Environmental Science
• Microbiology
• Biogeochemistry

Background:

• Polar regions face contamination from global pollutants, including methylmercury, which bioaccumulates in Arctic food chains.
• Microbial communities play a critical role in the biogeochemical cycling of elements, including toxic metals.

Purpose of the Study:

• To investigate the presence and expression of mercury-reductase genes (merA) in Arctic microbial communities.
• To assess the role of microbial mercury reduction in the biogeochemical cycling and environmental fate of mercury in the High Arctic.

Main Methods:

• Sampling of microbial biomass from Arctic coastal lagoons and marine macroalgae.
• Analysis of microbial DNA for the presence of diverse merA genes.
• Application of a kinetic redox model incorporating photoredox and mer-mediated reactions to quantify mercury transformation.

Main Results:

• First evidence of diverse merA gene expression in High Arctic microbes, primarily psychrophilic bacteria.
• Microbial mercury reduction significantly contributes to the production of volatile elemental mercury (Hg(0)) in Arctic waters.
• Mer-mediated reduction accounted for up to 68% of Hg(0) at the surface and 90% at greater depths, where light is attenuated.

Conclusions:

• Arctic microbial communities possess the genetic machinery to reduce mercury, influencing its environmental mobility and toxicity.
• Microbial redox transformations are a key driver of mercury biogeochemical cycling in polar ecosystems.
• Understanding these microbial processes is crucial for assessing mercury contamination risks in the Arctic.