Supplementary Tables.pdf

In this study, we demonstrate substantial enrichments of mercury (Hg) and methylmercury (MMHg), along with the presence of microbes capable of metabolizing mercuryHg in sediments of the Haima cold seep, South China Sea. Compared to the reference area, the sediments in the upper sediment column (0-12 cm) of the active-seep area were 2.4 times enriched in Hg and 10.5 times in methylmercuryMMHg. The maxima of MMHg/Hg ratio are about 8 and 18 times higher in the active-seep and inactive-seep area, respectively, than those in the reference area. The Hg stable isotope signatures in the active-seep area showed more distinct positive δ202Hg than those in the reference area. The slope of Δ199Hg/Δ201Hg with 1.23 ± 0.10 in the active-seep area indicate the occurrence of dark redox reactions. Genes related to mercuryHg methylation (hgcA), demethylation (merB) and reduction (merA) were phylogenetically associated with several bacterial and archaeal linages. We roughly estimated an additional 2,835 Mg mercuryHg and 12.6 Mg methylmercuryMMHg are stored in cold seep globally.