Heavy metals in marine mammals
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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 l.jpg

Heavy Metals in Marine Mammals

Das et al 2003

&

O’Hara et al 2003


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MM Context

  • Long lived – ? bowheads >100y

  • Predators

  • Bioaccumulators

  • Epizootics in relatively polluted regions such as Baltic, N. Sea and Med. Possibly associated with immunosuppression


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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?


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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



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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


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Routes

  • Lungs

  • Skin

  • Placenta

  • Milk

  • Mouth


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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)


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Organ distribution

  • Hg – Liver > Kidney > Muscle

  • Beluga slough 20% of Hg burden annually in skin

  • Cd – Kidney


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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


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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


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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


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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


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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


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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


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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.


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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.


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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


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Fluoride products in bottlenose dolphins (

  • 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


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Issues products in bottlenose dolphins (

  • 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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