Mercury accumulation, biomagnification, and relationships to δ13C, δ15N and δ34S of fishes and marine mammals in a coastal Arctic marine food web

Abstract

Combining mercury and stable isotope data sets of consumers facilitates the quantification of whether contaminant variation in predators is due to diet, habitat use and/or environmental factors. We investigated inter-species variation in total Hg (THg) concentrations, trophic magnification slope between δ¹⁵N and THg, and relationships of THg with δ¹³C and δ³⁴S in 15 fish and four marine mammal species (249 individuals in total) in coastal Arctic waters. Median THg concentration in muscle varied between species ranging from 0.08 ± 0.04 μg g^-1 dw in capelin to 3.10 ± 0.80 μg g^-1 dw in beluga whales. Both δ¹⁵N (r² = 0.26) and δ³⁴S (r² = 0.19) best explained variation in log-THg across consumers. Higher THg concentrations occurred in higher trophic level species that consumed more pelagic-associated prey than consumers that rely on the benthic microbial-based food web. Our study illustrates the importance of using a multi-isotopic approach that includes δ³⁴S when investigating trophic Hg dynamics in coastal marine systems.

Keywords: Coastal food web; Contaminants; Habitat; Stable isotopes; Sulfur; Trophic magnification slope; Trophic transfer.