Mercury contamination along the eastern coast of the United States: Assessment of the Diamondback terrapin, Malaclemys terrapin, as an indicator species
Arthur, Courtney Dawn
Owens, David Wm.
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Mercury (Hg) contamination has become a global issue in the past century. Malaclemys terrapin life history traits including wide distribution, site fidelity, and long lifespan, may suit it for contaminant studies. The purpose of this study was to determine if the diamondback terrapin, M. terrapin, shows local or regional variation as an indicator of Hg in estuaries. Isotope-dilution inductively coupled plasma mass spectrometry determined total mercury (THg) in M. terrapin blood and scute tissues on a local scale in Charleston, SC, and on a regional scale following a gradient of atmospheric Hg deposition in the southeastern United States. Mercury varied by sex and site for blood (F(8,63)=9.09, P<0.0001) and scutes (F(14,57)=10.17, P<0.0001). Atomic absorption spectroscopy determined THg in intertidal sediments from Charleston, which varied by site (F(3,16)=5.89, P=0.0066). Though sediment THg varied by site and validated the choice of local pristine and polluted sites, no correlation existed between sediments and blood (F(1,2)=0.37, P=0.604) or scutes (F(1,2)=0.52, P=0.547). Variation in tissue THg was explained by local and regional mercury contamination, though neither sexes nor tissue matrices always reflected the same trend. A more detailed look at the entire system, and in particular sediment chemistry, is needed to resolve the controls on mercury levels in M. terrapin. Uncertain conservation status makes M. terrapin a prime candidate for further study of estuarine pollution. Future studies should focus on population and health assessments in order to prioritize threats that are likely causing declines in M. terrapin populations.