Assessment of Potential Health Effects from Organochlorine Contaminants Exposure in Free-Ranging Northern Fur Seals (Callorhinus ursinus) Pups from St. George Island, Alaska
Kimberlee B. Beckmen1, DVM, MS; Gina M. Ylitalo2, MS; Rodney Towell3, BS; Rolf Ream3, BS; Jeff Stott4, MS, PhD
1Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks AK, USA; 2Environmental Conservation Division, Northwest Fisheries Science Center, NMFS/NOAA, Seattle WA, USA; 3National Marine Mammal Laboratory, NMFS/NOAA, Seattle WA, USA; 4Laboratory for Marine Mammal Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA
Abstract
The northern fur seal (Callorhinus ursinus) population that breeds on St. George Island, Alaska, declined at an annual rate of approximately 6% from 1980–1996. Previous studies found lower than expected return rates after initial post-weaning migrations. In order to examine the possible role of organochlorine contaminant-linked immunosuppression, two cohorts of pups and their dams were examined. Forty-two neonates were captured for blood sampling, vaccinated with tetanus toxoid and re-sampled at 4–6 wk later. In addition, matched dams of 33 were concurrently captured for blood and milk sampling. Organochlorine (OC) compounds were extracted from whole blood and milk then subjected to high-performance liquid chromatography to identify 14 selected individual polychlorinated biphenyl (PCB) congeners and DDT metabolites. Cellular immune function assays along with complete blood cell counts, serum retinol, serum thyroxine levels and tetanus antibody response were used as indicators of health status. The pup’s blood parameters were then compared to their individual and maternal OC congener profiles. PCB congener profiles of pup blood were better correlated to the dam’s milk than blood with variations due to age and other factors. Inter-annual differences in exposure levels and specific congener concentrations were apparent. The milk of young dams (presumably primiparous) and their neonate’s blood had significantly elevated levels of various congeners over that of older dam’s milk and neonate blood. Serum retinol and thyroxine levels, which are known to be decreased as part of the toxic effect of PCBs in laboratory animals, were negatively correlated to increasing toxic equivalency quotients (TEQs) and select congeners in pups. Functional lymphocyte proliferation responses to the mitogen ConA were decreased in correlation with increasing levels PCB congeners. The results of this study demonstrate the utility of using field-cryopreserve blood samples to monitor health status and potential OC contaminant exposure in living, free-ranging fur seal pups.