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Comparison of Mercury Burdens in Chronically Debilitated and Healthy Loggerhead Sea Turtles (Caretta caretta)



Russell D. Day, Jennifer M. Lynch, Craig A. Harms, Al L. Segars, Wendy M. Cluse, Matthew H. Godfrey, A. M. Lee, Margie Peden-Adams, Kelly Thorvalson, Mark Dodd, Terry Norton


An increase in the incidence of debilitated loggerhead sea turtle strandings in the southeastern U.S. has been observed in recent years. These turtles are characterized by emaciation and heavy burdens of external and internal parasites and bacterial infections, but the underlying cause of their condition is unknown. To further investigate, a health assessment was performed on stranded debilitated loggerhead turtles and contaminant levels in various tissue compartments were compared to healthy turtles. This portion of the study investigated the potential role of mercury (Hg) toxicity in the debilitated condition described above. Hematocrit, total protein, albumin, globulin, glucose, calcium, lymphocyte counts, heterophil/lymphocyte ratios, aspartate aminotransferase, uric acid, sodium, and chloride were measured in debilitated loggerheads. Although alterations were observed in many of these parameters relative to healthy animals, none of the aforementioned health indicators measured in debilitated loggerheads correlated with Hg concentrations in either red blood cells (RBCs) or plasma. The mercury concentration in RBCs was 129 (± 72) times higher than in plasma, causing a significant dilution of Hg in whole blood due to extreme anemia. Mercury levels in RBCs and scutes from debilitated turtles were similar or lower than those reported for healthy animals, indicating no elevation in Hg exposure before and during the progression of this condition. These findings suggest that Hg toxicity does not play a role in the debilitated loggerhead condition observed in the southeastern United States.
Journal of Wildlife Diseases


mercury, sea turtle, loggerhead, health, blood, scutes, keratin, plasma, red blood cells


Day, R. , Lynch, J. , Harms, C. , Segars, A. , Cluse, W. , Godfrey, M. , Lee, A. , Peden-Adams, M. , Thorvalson, K. , Dodd, M. and Norton, T. (2010), Comparison of Mercury Burdens in Chronically Debilitated and Healthy Loggerhead Sea Turtles (Caretta caretta), Journal of Wildlife Diseases, [online], (Accessed May 27, 2024)


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Created January 15, 2010, Updated February 17, 2017