Coastal Mussel (Mytilus spp.) Soft Tissues as Bioindicators of Methylmercury: Exploring the Relationship Between Condition Index and Methylmercury Concentrations.

We investigated total mercury (THg) and methylmercury (MeHg) concentrations in coastal mussels (Mytilus spp.) sampled from the Minas Basin, Bay of Fundy and evaluated the relationship with condition index (CI). THg concentrations were low in sediment (mean THg = 5.15 ± 2.11 ng/g dw; n = 6) and soft tissues (mean THg = 62.3 ± 13.7 ng/g; mean MeHg = 13.2 ± 6.3 ng/g; n = 57). The THg in tissues had no significant relationship with CI (Rs= -0.205, p = 0.126). MeHg in tissues were significantly and negatively correlated with condition index (Rs = -0.361, p = 0.006) indicating that healthier mussels (higher CI) have lower mercury content possibly due to elimination strategies or growth dilution.

Ecology and environmental characteristics influence methylmercury bioaccumulation in coastal invertebrates.

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.

Mercury bioaccumulation and speciation in coastal invertebrates: Implications for trophic magnification in a marine food web.

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.

The Complex Interactions Between Sediment Geochemistry, Methylmercury Production, and Bioaccumulation in Intertidal Estuarine Ecosystems: A Focused Review.

Due to their natural geochemistry, intertidal estuarine ecosystems are vulnerable to bioaccumulation of methylmercury (MeHg), a neurotoxin that readily bioaccumulates in organisms. Determining MeHg concentrations in intertidal invertebrates at the base of the food web is crucial in determining MeHg exposure in higher trophic level organisms like fish and birds. The processes that govern the production of MeHg in coastal ecosystems are influenced by many geochemical factors including sulfur species, organic matter, and salinity. The interactions of these factors with mercury are complex, and a wide variety of results have been reported in the literature. This paper reviews conceptual models to better clarify the various geochemical and physical factors that impact MeHg production and bioavailability in intertidal ecosystems.