No evidence of elevated mercury in sessile coastal biota exposed to Greenland glacial runoff

Melting glaciers have been claimed to be a significant and unaccounted-for source of mercury (Hg) in Greenland, raising concerns for communities, ecosystem health, and economics. Here we demonstrate, however, consistently low Hg concentrations in sessile organisms across >100 km spatial gradients and decadal time scales in three Southwest Greenland fjords exposed to glacial melt. Average Hg concentrations ranged 21.6–53.4 ng g −1 dw in the blue mussel Mytilus edulis , <7 ng g −1 dw in the macroalga Fucus vesiculosus , and 5.7–20.2 ng g −1 dw in Ascophyllum nodosum . These Hg concentrations in biota are low relative to international thresholds and detection limits and showed no temporal relationship with glacial and freshwater runoff. Our results therefore provide no evidence that Greenland glacial runoff is associated with elevated Hg concentrations in sessile coastal biota. Combined with previous studies on Hg in Greenland’s coastal zone, there is now substantial evidence against the claim that the Greenland Ice Sheet has implications for Hg budgets and coastal ecosystems.