A review on the distribution and transformation of dimethylmercury in marine environments

Methylmercury (MeHg) is the major form of mercury (Hg) that poses risks to humans and wildlife. Dimethylmercury (DMHg) is the most toxic organic mercury compound, and it plays an important role in the cycling of MeHg in the ocean. However, there is a lack of systematic review on DMHg in the marine environments. This review was divided into six sections: (i) detection of DMHg in marine environments, (ii) distribution of DMHg in marine environments and its influencing factors, (iii) the exchange fluxes of DMHg at the sea-air interface, (iv) potential formation pathways of DMHg in the ocean, (v) the degradation pathways of DMHg in the ocean, and (vi) the relationship between monomethylmercury (MMHg) and DMHg in the ocean. With the improvement of marine DMHg analysis methods and the research on the fate of DMHg in the ocean, our understanding of the biogeochemical cycle of DMHg in the ocean will be advanced in the future, e.g., the spatial distribution characteristics of DMHg in the ocean and its controlling factors, the mechanisms of DMHg formation and degradation in the ocean, including the key pathways, substrates, and key microorganisms and functional genes.