Because mercury bio-accumulates, and otters are SO carnivorous, they are like the canary in a coalmine for the detection of mercury. The Wisconsin Dept of Natural Resources asked all the otter trappers for the carcasses and tested various tissues for mercury levels. The levels were highest in fur, with descending concentrations in these tissues: liver, kidney, muscle, and brain. Methyl-mercury made up a greater percentage of total Hg in brain and muscle compared to liver and kidney tissue. So far none of the otters appears to be sickened by their mercury load. The levels in the fur are directly related to the levels in internal tracking, so I suspect future research may follow living otters to see what they're taking in. "A gradient" in tissue concentrations was noted from north to south, but they don't say which way the gradient goes. Perhaps more to the south, like in fish? We shall see.
SOURCES
http://dnr.wi.gov/environmentprotect/pbt/research/OtterSummaryAbstract.pdf
http://www.springerlink.com/content/m4pg0184615kr4hk/
http://www.ncbi.nlm.nih.gov/pubmed/17926081
Also, at http://www.glc.org/glad/projects/basu09/ they are monitoring eagles and otters for biomarkers. The specific aims of this proposal are: 1) Exposure Assessment : to determine tissue mercury and PBDE levels in river otters and bald eagles from several Great Lakes states, with a focus on animals collected from existing statewide monitoring programs in Michigan and Wisconsin; 2) Health Assessment : to determine river otter and bald eagle health status by means of neurochemical biomarker studies on key receptors (muscarinic, glutamate) and enzymes (monoamine oxidase, cholinesterase) in physiologically important brain regions; 3) Risk Characterization : to determine if there is a statistical association between mercury and PBDE exposure (Aim #1) and alterations in neurochemical biomarkers (Aim #2); and 4) Education and Capacity Building : to build capacity among academic researchers and government/state managers and to disseminate results to scientific and regulatory communities.
SOURCES
http://dnr.wi.gov/environmentprotect/pbt/research/OtterSummaryAbstract.pdf
http://www.springerlink.com/content/m4pg0184615kr4hk/
http://www.ncbi.nlm.nih.gov/pubmed/17926081
Also, at http://www.glc.org/glad/projects/basu09/ they are monitoring eagles and otters for biomarkers. The specific aims of this proposal are: 1) Exposure Assessment : to determine tissue mercury and PBDE levels in river otters and bald eagles from several Great Lakes states, with a focus on animals collected from existing statewide monitoring programs in Michigan and Wisconsin; 2) Health Assessment : to determine river otter and bald eagle health status by means of neurochemical biomarker studies on key receptors (muscarinic, glutamate) and enzymes (monoamine oxidase, cholinesterase) in physiologically important brain regions; 3) Risk Characterization : to determine if there is a statistical association between mercury and PBDE exposure (Aim #1) and alterations in neurochemical biomarkers (Aim #2); and 4) Education and Capacity Building : to build capacity among academic researchers and government/state managers and to disseminate results to scientific and regulatory communities.
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