Per- and polyfluorinated alkyl substances (PFASs) enter Arctic lakes through long-range atmospheric transport and local contamination, but their behavior in aquatic food webs at high latitudes is poorly understood. This study compared the concentrations of perfluorocarboxylates, perfluorosulfonates, and fluorotelomer sulfonates (FTS) in biotic and abiotic samples from six high Arctic lakes near Resolute Bay, Nunavut, Canada. Two of these lakes are known to be locally contaminated by a small airport and Arctic char (Salvelinus alpinus) from these lakes had over 100 times higher total [PFAS] when compared to fish from neighboring lakes. Perfluorononanoate (PFOA) and perfluorooctanesulfonate (PFOS) dominated in char, benthic chironomids (their main prey), and sediments, while pelagic zooplankton and water were dominated by lower chain acids and perfluorodecanesulfonate (PFDS). This study also provides the first measures of perfluoroethylcyclohexanesulfonate (PFECHS) and FTS compounds in water, sediment, juvenile char, and benthic invertebrates from lakes in the high Arctic. Negative relationships between [PFAS] and δ(15)N values (indicative of trophic position) within these food webs indicated no biomagnification. Overall, these results suggest that habitat use and local sources of contamination, but not trophic level, are important determinants of [PFAS] in biota from freshwater food webs in the Canadian Arctic.

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Dissolved organic matter (DOM) includes an array of carbon-based compounds that vary in size and structure and have complex interactions with mercury (Hg) cycling in aquatic systems. While many studies have examined the relationship between dissolved organic carbon concentrations ([DOC]) and methyl Hg bioaccumulation, few studies have considered the effects of DOM composition (e.g., protein-content, aromaticity). The goal of this study was to explore the relationships between total and methyl [Hg] in water, invertebrates, and fish and optically derived measures of DOM composition from 47 lake and river sites across a boreal watershed. Results showed higher aqueous total [Hg] in systems with more aromatic DOM and higher [DOC], potentially due to enhanced transport from upstream or riparian areas. Methyl [Hg] in biota were all positively related to the amount of microbial-based DOM and, in some cases, to the proportions of labile and protein-like DOM. These results suggest that increased Hg bioaccumulation is related to the availability of labile DOM, potentially due to enhanced Hg methylation. DOM composition explained 68% and 54% more variability in [Hg] in surface waters and large-bodied fish, respectively, than [DOC] alone. These results show that optical measures of DOM characteristics are a valuable tool for understanding DOM-Hg biogeochemistry.

It is commonly assumed that most (>95%) of the mercury (Hg) found in fish muscle is the toxic form, methylmercury (MeHg), due to its efficient assimilation and retention in biotic tissue. However, this assumption is largely based on studies examining the percentage of MeHg (%MeHg [the fraction of total Hg as MeHg]) in muscle from mostly large-bodied predatory fish; less is known about the %MeHg in smaller bodied individuals or those of different trophic guilds. The present study analyzed MeHg and total Hg concentrations in the muscle of 2 large-bodied piscivores (walleye and northern pike), one large-bodied benthivore (white sucker), and 2 small-bodied forage fish (sculpins and shiners) across a broad size range. We found substantially lower %MeHg than the commonly assumed 95% in several fish (e.g., 17 individuals had <70% MeHg). Muscle %MeHg significantly increased with size and age in all species except walleye, which had significantly higher %MeHg than pike or suckers, particularly in smaller and younger fish (e.g., 18-21% higher at 10 g; 5-11% higher at 500 g). Results of predictive modeling suggest that muscle %MeHg is higher in pelagic-feeding fish and those with lower lipid content, although model results varied significantly among species. According to our findings, total Hg measurement in muscle is not an appropriate proxy for MeHg in smaller fish from all species, an important consideration for future piscine Hg studies and monitoring. Environ Toxicol Chem 2018;37:2682-2691. © 2018 SETAC.

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