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Heavy Metals in Marine Mammals

Heavy Metals in Marine Mammals. Das et al 2003 & O’Hara et al 2003. MM Context. Long lived – ? bowheads >100y Predators Bioaccumulators Epizootics in relatively polluted regions such as Baltic, N. Sea and Med. Possibly associated with immunosuppression. Problems.

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Heavy Metals in Marine Mammals

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  1. Heavy Metals in Marine Mammals Das et al 2003 & O’Hara et al 2003

  2. MM Context • Long lived – ? bowheads >100y • Predators • Bioaccumulators • Epizootics in relatively polluted regions such as Baltic, N. Sea and Med. Possibly associated with immunosuppression

  3. Problems • Complex inorganic and organic mixtures • Multiple stressors – foraging, reproducing, fasting, moulting, migrating, predators, disease, habitat degradation. • Limited experimental opportunity • Most samples from dead stranded animals • de Swart 1996 seal pcb/ immuno study did not examine metal concentrations, only HAH’s. • Hard to distinguish natural from anthropogenic • Hg naturally high in Med, Cd in Arctic • Experiments mimic levels in wild? • Are high levels bio-available?

  4. Metals • Can be immunotoxic, although no clear indication in MM yet • Essential: Zn, Cu, Cr, Ni, Se, Al • Non-essential Hg, Cd, Pb • Cr, Ni and Pb usually low in MM (few µg/g dw) • Ringed seal stillbirth correlates with [Ni] in air in Finland • Zn, Cu, Cd and Hg are bigger concerns

  5. Das et al 2003

  6. Arctic • Higher in Greenland Arctic 15th century Inuit and seal hair than in N Sea today. Natural source. Same for porpoises. May reflect lack of organic binders in Arctic water. • Hg, CD, Zn and Cu levels vary across Arctic with natural sediment levels. • ? Exposed for millenia and well adapted

  7. Routes • Lungs • Skin • Placenta • Milk • Mouth

  8. Diet • Cephalopods concentrate Cd in viscera – Holsbeek saw high Cd in Sperm whale (Physeter) – see osteomalacia in humans – not seen in Pm • Bivalves transfer Cd and Pb to walrus. • Dugongs – High Cd and Zn. ? Results from low seagrass Cu augmenting intake • Minke whale: Hg Greenland >>>>Antarctic (fish vs krill)

  9. Organ distribution • Hg – Liver > Kidney > Muscle • Beluga slough 20% of Hg burden annually in skin • Cd – Kidney

  10. Hg • Me-Hg most lipid soluble and toxic form, so [ΣHg] poor indicator of Hg toxicity. Se demthylates Hg and reduces intake. Ratio important • Biomagnifies up chain from zooplankters • Easy placental transfer • Sensory and motor deficits, anorexia and lethargy • Hg in Tt hepatic lipofuchsin • Hi Hg in N Sea Pp ? Assoc with incr. parasitism

  11. Hg detoxification • Hg/Se mutual antagonism • Hg is demthylated – see mercuric selenide in hepatic macrophages – in Ziphius, striped dolphin, Tursiops and G mac also in lung assoc w C particles in latter 2 spp. – leads to high but non-toxic concentrations

  12. Hg in Faroes G melas • Faroese eat 1200-2900µg Hg/week • Health advisory – no viscera and meat & blubber only once per week • High Se may protect human consumer, but Weihe, Grandjean et al showed Hg associated cognitive deficits in human offspring • Beluga – hepatic Hg levels high but may not be a major human diet item

  13. Cd • Kidney, lung, cardiovascular, hemopoietic • Carcinogenic, mutagenic, teratogenic • Osteomalacia ‘itai-itai’ • Arctic ringed seals < 2000 µg/g dw (800 µg/g dw induces renal damage in humans), but no effects documented in seals: implies efficient detoxification and tolerance to high levels • High in baleen whales – no effects seen • Bowhead renal Cd levels of possible concern to human subsistence consumers

  14. Metalothioneins • High cysteine content – mainly in liver and kidney • High affinity for divalent cations such as Cu2+ and Zn2+ as well as Cd2+, Ag+, Hg2+ and Pb2+ • Lowest levels in stranded sperm whales - ? Cd tox part of the syndrome

  15. Organotins • Higher in coastal water animals • Higher in cetaceans than pinnipeds ( hair excretion) • High in liver and hair of Steller’s sea lion • TBT and DBT immunotoxic in vitro – Nakata et al 2002 – in Tt, Zc and humans • Little loss to offspring from mothers – adult M and F levels compare – cf. HAH Nakata et al 2002 Environmental PollutionVolume 120, Issue 2 , December 2002, Pages 245-253

  16. Fig. 2. Proliferation response of peripheral blood mononuclear cells (PBMCs) in two bottlenose dolphins following the treatment with non-ortho coplanar PCB congeners and butyltins. #: P<0.01.

  17. Fig. 5. Proliferation response of peripheral blood mononuclear cells (PBMCs) in bottlenose dolphins following the treatment with the mixture of butyltins and non-ortho coplanar PCB congeners and butyltins. #: P<0.01.

  18. Elevated accumulation of tributyltin and its breakdown products in bottlenose dolphins (Tursiops truncatus) found stranded along the U.S. Atlantic and Gulf coasts ? Immunosupression enhanced morbillivirus die- offs Kannan, et al 1997Environmental Science & Technology vol. 31, no. 1, pp. 296-301

  19. Fluoride • Fluoride concentration in fin whales higher than that normally occurring in any mammalian species, ranging from 4,340 to 18,570 ppm. – Significantly above the levels causing bony exostoses in sheep and cattle. Krill are high in Fl. Assume resistant – Landy et al 1991

  20. Issues • Many MM were over-exploited – some not recovering: vessel collision, gear entanglement, ? heavy metal impact, organic contaminants. • Some species directly compete with commercial fisheries, others do not • May have important community structure role as predators • Do metals impact immune function?

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