occurring as active uptake of Hg into the lichens occurred, and this Hg was strongly sequestered. Mason et al. (10.3389/fenvc.2025.1701684) detailed the air-sea exchange and mass balance for Hg and MMHg in the Gulf of Maine and concluded that external inputs of MMHg were not the primary driver of water column MeHg concentration, suggesting substantial water column methylation. Bakour et al. (10.3389/fenvc.2025.1559968) studied the impact of added cysteine and sulfide on Hg methylation and MMHg demethylation by a sulfate-reducing bacterium and found that the added ligands decreased methylation but had no impact on demethylation. Modeling suggested that the addition of the reduced sulfur reduced the rate of methylation by making Hg less bioavailable. These papers cover important research highlighting the complexity of the environmental chemistry of Hg and the complexities of the transformation between the different forms in the multiple compartments of the biosphere covered by these studies.
Mason et al. (2026) studied this question.