title: Assessment of neurotoxic effects of mercury in beluga whales (Delphinapterus leucas), ringed seals (Pusa hispida), and polar bears (Ursus maritimus) from the Canadian Arctic.
abstract: Marine mammals are indicator species of the Arctic ecosystem and an integral component of the traditional Inuit diet. The potential neurotoxic effects of increased mercury (Hg) in beluga whales (Delphinapterus leucas), ringed seals (Pusa hispida), and polar bears (Ursus maritimus) are not clear. We assessed the risk of Hg-associated neurotoxicity to these species by comparing their brain Hg concentrations with threshold concentrations for toxic endpoints detected in laboratory animals and field observations: clinical symptoms (>6.75 mg/kg wet weight (ww)), neuropathological signs (>4 mg/kg ww), neurochemical changes (>0.4 mg/kg ww), and neurobehavioral changes (>0.1mg/kg ww). The total Hg (THg) concentrations in the cerebellum and frontal lobe of ringed seals and polar bears were <0.5mg/kg ww, whereas the average concentration in beluga whale brain was >3mg/kg ww. Our results suggest that brain THg levels in polar bears are below levels that induce neurobehavioral effects as reported in the literature, while THg concentrations in ringed seals are within the range that elicit neurobehavioral effects and individual ringed seals exceed the threshold for neurochemical changes. The relatively high THg concentration in beluga whales exceeds all of the neurotoxicity thresholds assessed. High brain selenium (Se):Hg molar ratios were observed in all three species, suggesting that Se could protect the animals from Hg-associated neurotoxicity. This assessment was limited by several factors that influence neurotoxic effects in animals, including: animal species; form of Hg in the brain; and interactions with modifiers of Hg-associated toxicity, such as Se. Comparing brain Hg concentrations in wildlife with concentrations of appropriate laboratory studies can be used as a tool for risk characterization of the neurotoxic effects of Hg in Arctic marine mammals.
authors: Natural Resources and Environmental Studies, University of Northern British Columbia, 3333 University Way, Prince George, BC V2N 4Z9, Canada. Electronic address: krey@unbc.ca.
authors: Anke
authors: A
authors: Krey
authors: Natural Resources and Environmental Studies, University of Northern British Columbia, 3333 University Way, Prince George, BC V2N 4Z9, Canada. Electronic address: ostertag@unbc.ca.
authors: Sonja K
authors: SK
authors: Ostertag
authors: Center for Advanced Research in Environmental Genomics, University of Ottawa, 20 Marie-Curie, Ottawa, ON K1N 6N5, Canada. Electronic address: laurie.chan@uottawa.ca.
authors: Hing Man
authors: HM
authors: Chan
mesh_terms: D000818:Animals; D001110:Arctic Regions; D050643:Beluga Whale / Q000502:physiology; D002170:Canada; D010872:Caniformia / Q000502:physiology; D004784:Environmental Monitoring; D008628:Mercury / Q000633:toxicity*; D009420:Nervous System / Q000187:drug effects*; D046048:Seals, Earless / Q000502:physiology; D001503:Ursidae / Q000502:physiology; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D008628:Mercury
keywords: Beluga whales; Mercury; Neurotoxicity; Polar bear; Ringed seal; Threshold