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Studies on mercury bioaccumulation and biomagnification in coastal invertebrates in eastern Canada are limited, but these data are necessary to determine risk of mercury exposure effects in upper trophic level organisms. We quantified methylmercury (MeHg), total mercury (THg), and stable isotopes of δ13C and δ15N in 14 species of invertebrates in the Minas Basin. The overall mean concentration of MeHg (12.78 ± 11.23 ng/g dw) was approximately 10 times below the Canadian guideline for the protection of wildlife consumers like fish and birds of 157.20 ng/g dry weight (dw). Invertebrates at higher trophic positions (δ15N) had greater THg and particularly MeHg. The Trophic Magnification Factors (TMF) for MeHg and THg (1.59 and 1.21 respectively) were similar to others reported in studies of food webs containing higher trophic level organisms. [Display omitted] • Mean invertebrate MeHg was ∼10× below Canadian environmental health guidelines. • Hg Trophic Magnification Factors comparable to coastal food webs with top predators • Quantifying invertebrate [Hg] fills data gap in coastal food webs in Eastern Canada. [ABSTRACT FROM AUTHOR]

Quantifying mercury (Hg) concentrations in invertebrates is fundamental to determining risk for bioaccumulation in higher trophic level organisms in coastal food webs. Bioaccumulation is influenced by local mercury concentrations, site geochemistry, individual feeding ecologies, and trophic position. We sampled seven species of invertebrates from five coastal sites in the Minas Basin, Bay of Fundy, and determined body concentrations of methylmercury (MeHg), total mercury (THg), and stable isotopes of nitrogen (δ15N) and carbon (δ13C). To evaluate the effects of environmental chemistry on Hg production and bioaccumulation, bulk sediments from all sites were analysed for THg, %Loss on ignition (LOI) (carbon), and sulfur isotopes (δ34S), and concentrations of MeHg, Total Organic Carbon (TOC), sulfate, and sulfide were measured in porewaters. The mean concentration of MeHg in tissues for all invertebrates sampled was 10.03 ± 7.04 ng g−1). MeHg in porewater (mean = 0.22–1.59 ng L−1) was the strongest predictor of invertebrate MeHg, but sediment δ34S (−0.80–14.1‰) was also a relatively strong predictor. δ34S in tissues (measured in three species; Corophium volutator , Ilyanassa obsoleta , and Littorina littorea) were positively related to MeHg in invertebrates (r = 0.55, 0.22, and 0.71 respectively), and when used in combination with δ15N and δ13C values improved predictions of Hg concentrations in biota. Hg concentrations in the amphipod Corophium volutator (mean MeHg = 10.60 ± 1.90 ng g−1) were particularly well predicted using porewater and sediment chemistry, highlighting this species as a useful bioindicator of Hg contamination in sediments of the Bay of Fundy. [Display omitted] • Porewater MeHg was the strongest environmental predictor of invertebrate MeHg. • Tissue δ34S strengthened predictions of MeHg concentrations in coastal invertebrates. • Corophium volutator may be effective bioindicator for coastal Hg contamination. [ABSTRACT FROM AUTHOR]

Daytime volatilization of gaseous elemental mercury (Hg(0) aq) is a significant mechanism for mercury removal from aquatic systems and potentially limits the production and bioaccumulation of methylmercury. Changes in incoming solar radiation (in the ultraviolet range), dissolved organic matter, salinity, and total suspended particles were investigated concurrently with several mercury species (Hg(0) aq , dissolved total mercury (THg), easily reducible mercury (ERM), and mercury associated with total suspended solids (THg TSS)) during daylight hours near the mouth of a hypertidal river. There were no predictable temporal changes observed for Hg(0) aq in unfiltered surface water. Hg(0) aq ranged from 0 to 12 pg L−1, THg ranged from 0 to 492 pg L−1, ERM ranged from 13 to 381 pg L−1, and THg TSS ranged from <1.58 ng g−1 to 261.32 ng g−1. The range of Hg(0) aq predicted by the empirical model was similar to measured ERM concentrations, but it was shown that ERM did not significantly predict in-situ photoreducible Hg(II) (Hg(II) RED). Production of Hg(0) aq appears to largely be suppressed by suspended solids, which limits ultraviolet radiation transmission through surface water. Comparison of these results to an empirical model developed for this site to predict Hg(0) aq indicates that significantly more mercury is available for photoreduction near the mouth of the tidal river, and that Hg(II) will likely photoreduce quickly when TSS levels decrease with ocean mixing. [Display omitted] • Divalent mercury photoreduction lessens mercury concentrations in ecosystems. • Estuarine water samples were taken every 0.5 h from sunrise to sunset. • Empirical model predicts higher mercury photoreduction than measured in the field. • High suspended solids limited mercury photoreduction. [ABSTRACT FROM AUTHOR]