► Unpublished and published data were compiled for Arctic fish, birds, and mammals. ► These data were compared to available toxicological threshold limits. ► Toothed whales, polar bears, and some bird and fish species exceeded the limits. ► Increasing mercury concentrations are observed for some Arctic species. ► These exceeded thresholds and increasing Hg trends are of concern. a b s t r a c t a r t i c l e i n f o This review critically evaluates the available mercury (Hg) data in Arctic marine biota and the Inuit population against toxicity threshold values. In particular marine top predators exhibit concentrations of mercury in their tissues and organs that are believed to exceed thresholds for biological effects. Species whose concentrations exceed threshold values include the polar bears (Ursus maritimus), beluga whale (Delphinapterus leucas), pilot whale (Globicephala melas), hooded seal (Cystophora cristata), a few seabird species, and landlocked Arctic char (Salvelinus alpinus). Toothed whales appear to be one of the most vulnerable groups, with high concentrations Science of the Total Environment 443 (2013) [775][776][777][778][779][780][781][782][783][784][785][786][787][788][789][790]

Blood and epidermal biopsies from free-ranging Tursiops truncatus captured and released during either summer or winter health assessments in Sarasota Bay, FL, were evaluated for concentrations of mercury, selenium, stable isotopes (d(13)C and d(15)N), and blood glutathione peroxidase activity in conjunction with routine hematology and serum chemistry panels. Major objectives were to: 1) quantify and describe relationships among mercury, selenium, glutathione peroxidase, and stable isotopes of C and N in blood and epidermis; 2) elucidate major parameters that influence blood mercury and glutathione peroxidase activity; 3) relate measures of tissue mercury, selenium, and glutathione peroxidase to specific ecological, hematological, morphological, or life history parameters, including season, sex, age, and trophic level. Mercury in both tissues examined is almost exclusively methylmercury. Epidermal concentrations of mercury and selenium reflect their respective amounts in blood, albeit at several times blood concentrations of mercury. The strong association between blood mercury and serum selenium, in conjunction with a lack of significant correlation between blood mercury and glutathione peroxidase, implies that a substantial proportion of blood mercury is affiliated with another selenium-containing moiety or is related to recent dietary intakes (e.g., trophic level, intensive fish consumption). Circulating blood mercury may be described in terms of serum selenium concentration, along with interaction terms among serum selenium, blood d(15)N, and age. Current selenium concentrations in Sarasota Bay dolphins appear adequate for maintenance of blood glutathione peroxidase activity. However, dolphins evidently are subject to seasonal exacerbation of oxidative stress, which might render them more vulnerable to toxic effects of mercury.

Total Hg concentration was measured in hair and whole blood of 52 adult Southern Beaufort Sea polar bears (Ursus maritimus) captured in the spring of 2005. Stable isotopic signatures (i.e., 13C/12C, delta13C; 15N/14N, delta15N) in hair and two blood compartments (packed blood cells/clot and serum) were determined to assess the variation of Hg concentrations among polar bears in relation to their feeding ecology and other biological factors. Concentrations of Hg in hair and blood (2.2-23.9 microg/g dry wt and 0.007-0.213 microg/g wet wt, respectively) were within the range of values previously reported for polar bears in Canada and East Greenland. Mercury concentration in hair from females was higher than that in hair from males, and concentration was related to interactions between delta13C, delta15N, and longitude of capture location. Mercury concentrations in hair were inversely correlated to delta13C in hair and blood, suggesting that polar bears with greater total Hg concentrations fed more on pelagic prey, such as ringed seals or beluga whale, than on benthic prey. Variability in Hg concentrations in polar bear hair and blood may be the result of intraspecific or regional variation in prey selection rather than strictly trophic level interactions.

We examined biomarkers of selenium status (whole blood Se, serum Se, and glutathione peroxidase activity) and thyroid status (concentrations and ratios of thyroxine, T4, and tri-iodothyronine, T3, and albumin) in polar bears to assess variations among cohorts, and relationships to circulating concentrations of contaminants. Concentrations of total mercury (Hg) in whole blood were similar among cohorts (prime aged males and females, older animals ages ≥ 16 years, and young animals ages 1 – 5 years; 48.44 ± 35. 81; p = 0.253). Concentrations of sum of seven polychlorinated biphenyls (ΣPCB7) in whole blood were greater in females (with and without cubs, 26.44 ± 25.82 ng/g ww) and young (26.81 ± 10.67 ng/g ww) compared to males (8.88 ± 5.76 ng/g ww, p < 0.001), and significantly related to reduced body condition scores (p < 0.001). Concentrations of Se and albumin were significantly greater in males than females (whole blood Se, males, 42.34 pmol/g ww; females, 36.25 ± 6.27 pmol/g ww, p = 0.019; albumin, males, 4.34 ± 0.34 g/dl, females, 4.10 ± 0.29 g/dL, p = 0.018). Glutathione peroxidase activity ranged from 109.1 – 207.8 mU/mg hemoglobin, but did not differ significantly by sex or age (p > 0.08). Thyroid hormones were greater in females (solitary females and females with cubs) compared to males (p < 0.001). Biomarkers of Se status and concentrations of T3 were significantly positively related to Hg in all prime aged polar bears (p < 0.03). Albumin concentrations were significantly positively related to total TT4, and significantly negatively related to concentrations of ΣPCB7 (p < 0.003). Total thyroxine (TT4) was significantly negatively associated with blood concentrations of ΣPCB7 in solitary females (p = 0.045). These data suggest that female polar bears were more susceptible to changes in blood-based biomarkers of selenium and thyroid status than males. Further classifications of the physiologic states of polar bears and repeated measures of individuals over time are needed to accurately assess the biological impact of combined toxicant exposures.

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