Effects of Mercury on Hepatic, Thyroid, Renal, and Endocrine Function in Atlantic Bottlenose Dolphins (tursiops truncatus) Along the Eastern Coast of Florida and South Carolina
IAAAM 2009
Adam M. Schaefer1; Hui-Chen W. Stavros2; John Reif3; Juli D. Goldstein1; Patricia A. Fair2; Gregory D. Bossart1
1Harbor Branch Oceanographic Institution at Florida Atlantic University, Ft. Pierce, FL, USA; 2Department of Environmental and Radiological Health Sciences, Colorado State University, Ft. Collins, CO, USA; 3Center for Coastal Environmental Health and Biomolecular Research, NOAA, NOS, Charleston, SC, USA

Abstract

Heavy metal contamination of mercury (Hg) in cetaceans has been documented worldwide in tissues from dead and stranded animals, reflecting a growing environmental burden of this metal in marine ecosystems. However, the physiological effects of Hg contamination on free-ranging live cetaceans remain largely unexplored. The current study examined both blood and skin samples collected from two populations of free-ranging Atlantic bottlenose dolphins (Tursiops truncatus) to examine the correlation between increasing levels of mercury with measures of hepatic, thyroid, renal, and endocrine function.3,4 A total of 121 dolphins examined between 2002 and 2005 were screened for trace metals as a part of the Bottlenose Dolphin Health and Environmental Risk Assessment study (HERA). Animals were sampled in the Indian River Lagoon, FL and the estuarine waters of Charleston, SC. We used multivariate linear regression to evaluate the effects skin and blood Hg on multiple endpoints while controlling for animal age and capture site. A positive association between blood Hg concentration and blood urea nitrogen (BUN) (p < 0.01) was observed. The increase in BUN suggests possible renal impairment but the lack of similar findings for other kidney function measures such as creatinine warrants further investigation. Total 3,3'-5 triiodothyronine (T3) and free thyroxine (T4) were negatively associated with skin Hg in the linear model. In addition, adrenocorticotrophin (ACTH) (p < 0.05) and estradiol (p < 0.01) were positively associated with skin Hg. Previous work in terrestrial mammals suggests selenium (Se) deficiency could play a role in decreased thyroid hormone production.1,2 A negative association between both measures of Hg and Se was observed in this study. Free T4, testosterone, aldosterone, and progesterone were not associated with Hg concentration in any models. Results of the study indicate possible physiological impairments as a consequence of increasing burden of Hg. Negative associations between Hg and thyroid hormones have not been previously reported in marine mammals. This study describes the first attempt to link Hg exposure to physiological impairment in free-living dolphins in order to fully explore the detrimental role of Hg contamination on free-ranging marine mammal health.

Acknowledgments

This work was conducted under NMFS permit 998-1678 issued to Dr. Gregory Bossart as part of the Health and Risk Assessment of Bottlenose Dolphins Project (HERA) conducted in the Indian River Lagoon, FL and the Coastal waters of Charleston, SC. Special thanks toStephen D. McCulloch and the numerous collaborators and volunteers who participated in the HERA project.

References

1.  Beckett G.J., D.A. MacDougall, F. Nicol, and J.R Arthur. 1989. Inhibition of type I and type II iodothyronine deiodinase activity in rat liver, kidney and brain produced by selenium deficiency. Biochem J 259: 887-892.

2.  Beckett G.J., F. Nicol, D. Proudfoot, K. Dyson, G. Loucaides, and J.R Arthur. 1990. The changes in hepatic enzyme expression caused by selenium deficiency and hypothyroidism in rats are produced by independent mechanisms. Biochem J 266: 743-747.

3.  Stavros H.C., G.D. Bossart, T.C. Hulsey, and P.A Fair. 2007. Trace element concentrations in skin of free-ranging bottlenose dolphins (Tursiops truncatus) from the southeast Atlantic coast. Sci Total Envir 388: 300-315.

4.  Stavros H.C., G.D. Bossart, T.C. Hulsey, and P.A. Fair. 2008. Trace element concentrations in blood of free-ranging bottlenose dolphins (Tursiops truncatus): Influence of age, sex and location. Mar Pollut Bull 56: 348-379.

 

Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

Adam M. Schaefer
Marine Mammal Research and Conservation Program Center for Marine Ecosystems Health Harbor Branch Oc
Florida Atlantic University
Ft. Pierce, FL, USA


Friendly Reminder to Our Colleagues: Use of VIN content is limited to personal reference by VIN members. No portion of any VIN content may be copied or distributed without the expressed written permission of VIN.

Clinicians are reminded that you are ultimately responsible for the care of your patients. Any content that concerns treatment of your cases should be deemed recommendations by colleagues for you to consider in your case management decisions. Dosages should be confirmed prior to dispensing medications unfamiliar to you. To better understand the origins and logic behind these policies, and to discuss them with your colleagues, click here.

Images posted by VIN community members and displayed via VIN should not be considered of diagnostic quality and the ultimate interpretation of the images lies with the attending clinician. Suggestions, discussions and interpretation related to posted images are only that -- suggestions and recommendations which may be based upon less than diagnostic quality information.

CONTACT US

777 W. Covell Blvd., Davis, CA 95616

vingram@vin.com

PHONE

  • Toll Free: 800-700-4636
  • From UK: 01-45-222-6154
  • From anywhere: (1)-530-756-4881
  • From Australia: 02-6145-2357
SAID=27