Assessing the utility of sulfur isotope values for understanding mercury concentrations in water and biota from high Arctic lakes

Methylmercury (MeHg) biomagnifies through aquatic food webs resulting in elevated concentrations in fish globally. Stable carbon and nitrogen isotopes are frequently used to determine dietary sources of MeHg and to model its biomagnification. However, given the strong links between MeHg and sulfur cycling, we investigated whether sulfur isotopes (δ34S) would improve our understanding of MeHg concentrations ([MeHg]) in Arctic lacustrine food webs. Delta34S values and total mercury (THg) or MeHg were measured in water, sediments and biota from 6 lakes near Resolute Bay, Nunavut. In two lakes impacted by historical eutrophication, aqueous sulfate δ34S was ~8‰ more positive than sedimentary δ34S, suggestive of bacterial sulfate-reduction in the sediment. In addition, aqueous δ34S showed a significant positive relationship with [MeHg] across lakes. Within taxa across lakes, [THg] in Arctic char muscle and [MeHg] in their main prey, chironomids, were positively related to their δ34S values across lakes, but inconsistent relationships were found across entire food webs among lakes. Across lakes, nitrogen isotopes were better predictors of biotic [THg] and [MeHg] than δ34S within this dataset. Our results show significant linkages between Hg and S biogeochemistry in high Arctic lakes which is an important consideration given anticipated climate-mediated changes in nutrient cycling.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author