Carbon dynamics control contemporary mercury burial in Arctic Ocean sediments

Understanding the high mercury concentrations observed in Arctic ecosystems requires in-depth knowledge of mercury cycling. Here, we show that variations in mercury concentration in the sediments of the North American Arctic Margin and the Arctic Ocean basins can be explained by carbon sources and cycling. Sedimentary mercury concentrations are predicted (p < 0.001) considering three carbon sources and, in some areas, the recapture of soluble mercury released during burial. Terrigenous organic carbon dominates mercury delivery (50-90%) in the western North American Arctic Margin, whereas inorganic carbon predominates at many eastern sites (40-70%). Marine organic carbon contributes <15% of the total mercury concentration. Mercury–organic carbon endmember ratios of terrigenous and marine organic carbon are higher in deep Arctic Ocean basins than in the continental margin, likely due to greater organic matter remineralization during transit. The observed enrichment in mercury toward the sediment surface results from remineralization of organic carbon, not from an increase in mercury flux. Mercury concentrations in sediments of the North American Arctic Margin and the Arctic Ocean basins can be entirely explained by carbon sources and cycling, according to analysis of sediment cores from the polar ocean.