Methylmercury formation in coastal seas: understanding risks associated with permanent and temporary oxygen deficiency

Mercury (Hg) accumulates in aquatic biota as neurotoxic methylmercury (MeHg) and is considered one of the top ten chemicals of public health concern.

Oxygen deficiency is spreading in coastal seas and the global ocean which could increase MeHg formation by anaerobic microorganisms and MeHg exposure to marine food webs and thereby threaten fishery as an ecosystem service in many regions.

Our understanding of the mechanisms and drivers for MeHg formation under such scenarios is however insufficient, hindering quantitative predictions and risk management.We recently demonstrated a correlation between MeHg formation rate and expression of the genes hgcAB, which mediate this process, in oxygen deficient coastal seas.

We will build on this discovery and describe mechanistic principles for MeHg formation and test the hypothesis that MeHg formation rate and amount can be predicted by hgcAB gene expression and Hg availability in brackish and marine coastal seas with permanent and temporary oxygen deficiency.

We will carry out the studies in the Baltic Sea and Norwegian fjords and interact with a project studying Hg cycling genes at global scale.

Through this synergy we aim to derive both the mechanistic principles and a general predictive model for MeHg formation in seas and the ocean.The project will serve society by providing missing knowledge to understand and predict how MeHg formation in different marine systems will be impacted by declining oxygen.