Partitioning of Contaminants between Blubber, Blood and Milk in Free-Ranging Bottlenose Dolphins: Implications for Bio-monitoring

Jennifer Yordy^{1, 2}, John Kucklick², Randall S. Wells³, Brian Balmer³, Bob Swarthout², and Teresa K. Rowles⁴

¹ Marine Biomedical and Environmental Sciences Center, Medical University of South Carolina, Charleston, SC

² National Institute of Standards and Technology, Charleston, SC

³ Chicago Zoological Society, c/o Mote Marine Laboratory, Sarasota, FL

⁴ National Marine Fisheries Service, Marine Mammal Health and Stranding Response Program, Silver Spring, MD

Concerns regarding the accumulation of organohalogen contaminants in marine mammals and the potential link to unusual mortality events, emerging diseases, survival and reproductive success have prompted increases in bio-monitoring efforts.  Exposure to organohalogen compounds, including polychlorinated biphenyls (PCBs) and pesticides has been associated with adverse health effects such as immunotoxicity, carcinogenicity and endocrine disruption in other mammals. Research investigating the health effects of these compounds in live, free ranging marine mammal populations requires the collection of non-lethal tissue samples for contaminant analysis that are indicative of whole body burdens.  Blubber contains >90% of total body burden concentrations of organic contaminants, hence it is currently the most common tissue used for bio-monitoring efforts.  However, due to the invasive nature of the biopsy procedure, short-term repeated blubber collections are not feasible for wild or captive populations.  Blood and milk can be collected less invasively; however the use of these tissues as predictors of blubber concentrations or body burden and risk has not been adequately demonstrated. To establish the utility of blood or milk as potential matrices for organohalogen determination, the Sarasota Dolphin Research Program collected full depth blubber biopsies, plasma and milk samples, when available, from free-ranging bottlenose dolphins in Sarasota Bay, Florida.  All samples were analyzed for organochlorine pesticides and PCBs by gas-chromatography-mass spectrometry (GC-MS).  Analyses of blubber (n=21) and plasma samples (n=12) collected during February 2004 show a strong positive correlation between total PCB concentrations and 4,4’-DDE on a wet weight basis (r²=0.90; r²=0.97, respectively), indicating plasma may serve as a predictor of organohalogen concentrations in blubber.  However, PCB and 4,4’-DDE milk concentrations were not strongly correlated with concentrations in blubber (r²=0.35) or in plasma (r²=0.58), suggesting milk should not be used to estimate body burden concentrations.  Analysis of additional samples spanning several years and seasons is currently underway.