Immune Changes in Northern Gulf of Mexico Bottlenose Dolphin Populations Associated with the Deepwater Horizon Oil Spill
The explosion of the Deepwater Horizon oil exploration platform on April 20, 2010 resulted in an unprecedented release of oil (estimated at 4.9 million barrels) in the Gulf of Mexico. Comprehensive health assessments were conducted on bottlenose dolphins in Barataria Bay, Louisiana, in 2011 and 2013 as well as in Mississippi Sound, Mississippi, in 2013, to assess potential health effects resulting from exposure to oil. Results were compared to those for Sarasota Bay, Florida, dolphins that were not exposed to oil (sampled in 2011, 2012 and 2013). Assessment of immune functions demonstrated a consistent and significant increase in T lymphocyte proliferation (with both Con A and PHA) in the 2011 Barataria Bay dolphins compared to the Sarasota Bay dolphins, at both suboptimal and optimal concentrations of mitogens. A significant increase in B cell proliferation was also observed in Barataria Bay (2011 and 2013) compared to Sarasota Bay dolphins. No significant differences in proliferation were observed in the absence of mitogens. Neutrophil and monocyte phagocytosis were consistently lower in 2013 Barataria Bay and Mississippi Sound dolphins compared to Sarasota Bay dolphins, although lower phagocytosis indices were not observed in 2011 Barataria Bay dolphins.
Immune changes observed in Barataria Bay dolphins are compatible with immunotoxicity and are consistent with changes observed in mink experimentally exposed to oil. A consequence of T cell immunotoxicity is increased susceptibility to infectious diseases, including intracellular pathogens. These immune changes may help explain some of the observed health issues in Barataria Bay dolphins1,2 as well as the unusual mortality event of dolphins in the northern Gulf of Mexico.3
1. Schwacke LH, Smith CR, Townsend FI, Wells RS, Hart LB, Balmer BC, Collier TK, De Guise S, Fry MM, Guillette LJ Jr, Lamb SV, Lane SM, McFee WE, Place NJ, Tumlin MC, Ylitalo GM, Zolman ES, Rowles TK. Health of common bottlenose dolphins (Tursiops truncatus) in Barataria Bay, Louisiana, following the Deepwater Horizon oil spill. Environ Sci Technol. 2014;48(1):93–103.
2. Smith CR, Ivancic M, Schwacke LH, Wells RS, Balmer BC, Venn-Watson S, Rowles TK. Comparison of pulmonary ultrasound findings in two populations of wild bottlenose dolphins, Tursiops truncatus. In: Proceedings of the IAAAM Annual Conference; 2013.
3. Venn-Watson S, Litz J, Colegrove K, Kinsel M, Garrison L, Terio K, Carmichael R, Fougeres E, Mase-Guthrie B, Ewing R, Shannon D, Shippee S, Smith S, Staggs L, Stratton E, Tumlin M, Rowles T. Update on the northern Gulf of Mexico cetacean unusual mortality event, 2010–2013: bottlenose dolphins (Tursiops truncatus). In: Proceedings of the IAAAM Annual Conference; 2013.