Mercury and Selenium: A Contaminant and Nutrient Interaction Assessment
By Carla Willetto, DVM, Victoria Woshner, DVM, PhD, and Todd O'Hara, DVM, PhD

Veterinary Environmental Toxicology Services (VETS) and the new Wildlife Toxicology Laboratory at the Institute of Arctic Biology (IAB) at the University of Alaska Fairbanks (UAF) have teamed up with Dr. Victoria Woshner to address selenium and mercury from a “functional” perspective in bottlenose dolphins sampled in the Sarasota Bay area. Selenium and mercury interact in a yet unknown way that likely alters the toxicity of mercury and alters the nutritional and toxic properties of selenium in cetaceans. For this reason we proposed to include functional assays (such as glutathione peroxidase) in the suite of indicators to address mercury and selenium status in bottlenose dolphins in concert with the current sampling for determining mercury and selenium concentrations in blood and skin.  In a few animal and human studies it was observed that deficiency of selenium could cause pregnancy complications.  Therefore, we propose to evaluate the blood and plasma levels of mercury and selenium, and glutathione peroxidase in blood to better develop a functional understanding of this mercury and selenium interaction and the health status of the Sarasota dolphin population.

Preliminary data indicate that the mean total mercury concentration in whole blood of 31 Sarasota bottlenose dolphins is about 100 fold higher than the recommended threshold level established for humans by the US Environmental Protection Agency.  It is recommended that people who are found to have “elevated” blood mercury levels decrease their fish intake – not a feasible option for the dolphins. However, how meaningful is this criteria level to a fish eating small cetacean?  Some cetaceans exhibit even higher levels of mercury in their blood.  Research to further elucidate the relationships between mercury and selenium and health, and to validate the functional assay is continuing, with the assistance of Ms. Katrina Knott.  Funding for this research has been provided by NOAA Fisheries, through the Chicago Zoological Society.