Subsurface seawater methylmercury maximum explains biotic mercury concentrations in the Canadian Arctic

Mercury (Hg) is a contaminant of major concern in Arctic marine ecosystems. Decades of Hg observations in marine biota from across the Canadian Arctic show generally higher concentrations in the west than in the east. Various hypotheses have attributed this longitudinal biotic Hg gradient to regiona...

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Bibliographic Details
Published in:Scientific Reports
Main Authors: Wang, Kang, Munson, Kathleen M., Beaupré-Laperrière, Alexis, Mucci, Alfonso, Macdonald, Robie W., Wang, Feiyue
Format: Report
Language:English
Published: Nature 2020
Subjects:
methylmercury
Arctic
mercury
marine ecosystem
biomagnification
Baffin Bay
Canada
Canadian Arctic Archipelago
Arctic Archipelago
ArcticNet
Baffin
canada basin
Labrador Sea
Zooplankton
Online Access:http://hdl.handle.net/1993/34764
https://doi.org/10.1038/s41598-018-32760-0
Description
Summary:Mercury (Hg) is a contaminant of major concern in Arctic marine ecosystems. Decades of Hg observations in marine biota from across the Canadian Arctic show generally higher concentrations in the west than in the east. Various hypotheses have attributed this longitudinal biotic Hg gradient to regional differences in atmospheric or terrestrial inputs of inorganic Hg, but it is methylmercury (MeHg) that accumulates and biomagnifies in marine biota. Here, we present high-resolution vertical profiles of total Hg and MeHg in seawater along a transect from the Canada Basin, across the Canadian Arctic Archipelago (CAA) and Baffin Bay, and into the Labrador Sea. Total Hg concentrations are lower in the western Arctic, opposing the biotic Hg distributions. In contrast, MeHg exhibits a distinctive subsurface maximum at shallow depths of 100–300m, with its peak concentration decreasing eastwards. As this subsurface MeHg maximum lies within the habitat of zooplankton and other lower trophic-level biota, biological uptake of subsurface MeHg and subsequent biomagnification readily explains the biotic Hg concentration gradient. Understanding the risk of MeHg to the Arctic marine ecosystem and Indigenous Peoples will thus require an elucidation of the processes that generate and maintain this subsurface MeHg maximum. Natural Science and Engineering Research Council (NSERC) of Canada, ArcticNet, the Canadian Arctic GEOTRACES program, and the Canada Research Chairs Program.

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