Low Reproductive Success Rates Among Bottlenose Dolphins in the Wake of the Deepwater Horizon Oil Spill
IAAAM 2016
Cynthia R. Smith1*; Teresa K. Rowles2; Kathleen M. Colegrove3; Nicholas M. Kellar4; Suzanne M. Lane5; Brian C. Balmer5,6; Kevin Barry7; Michael Kinsel3; Jennifer Litz8; Todd R. Speakman5; Forrest I. Townsend9; Stephanie Venn-Watson1; Randall S. Wells6; Eric S. Zolman5; Lori H. Schwacke5
1National Marine Mammal Foundation, San Diego, CA, USA; 2National Marine Fisheries Service, Office of Protected Resources, National Oceanic and Atmospheric Administration, Silver Spring, MD, USA; 3University of Illinois, Zoological Pathology Program, Maywood, IL, USA; 4National Marine Fisheries Service, Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration, La Jolla, CA, USA; 5National Centers for Coastal Ocean Science, Hollings Marine Laboratory, National Oceanic and Atmospheric Administration, Charleston, SC, USA; 6Chicago Zoological Society, c/o Mote Marine Laboratory, Sarasota, FL, USA; 7National Marine Fisheries Service, Southeast Fisheries Science Center, National Oceanic and Atmospheric Administration, Mississippi Laboratories, Pascagoula, MS, USA; 8National Marine Fisheries Service, Southeast Fisheries Science Center, National Oceanic and Atmospheric Administration, Miami, FL, USA; 9Bayside Hospital for Animals, Fort Walton Beach, FL, USA


In the aftermath of the Deepwater Horizon (DWH) disaster, impacts to bottlenose dolphins (Tursiops truncatus) in coastal areas of the northern Gulf of Mexico (NGOM) were well documented.1-5 Studies of live dolphins and necropsies of recovered carcasses within the DWH oil spill footprint confirmed lung injury and adrenal gland lesions consistent with known effects of oil or petroleum-associated compounds.1-3 Reproductive impacts were also studied in both live and dead dolphins, with a focus on the heaviest oiled coastal regions. For live animal studies, reproductive failure rates were evaluated for five years during and after the spill (2010–2015) in two NGOM bottlenose dolphin stocks exposed to DWH oil (Barataria Bay, LA, and Mississippi Sound, MS/AL).1,4 Pregnancy was determined from either ultrasound examinations during capture-release health assessments or endocrine evaluations of blubber tissue collected from dart biopsies. Follow-up photo-identification surveys of the two stocks were used to track the status of pregnant females and any associated neonate calves for a minimum of one year after the initial pregnancy detection. For all pregnant females tracked, individuals seen with a calf (reproductive success) and without one (reproductive failure) were recorded. The resulting estimated reproductive success rates for dolphins living in areas not impacted by the DWH oil spill (i.e., Sarasota Bay, FL; Indian River Lagoon, FL; and Charleston Harbor, SC) were three-fold higher than the reproductive success rates for both NGOM stocks within the DWH oil spill footprint. Results from the stranded animal studies showed that dead perinate dolphins in the oil spill footprint had a higher prevalence of atelectasis (88% vs. 15%), fetal distress (87% vs. 27%), and in utero pneumonia (65% vs 19%) compared to reference perinates.5 This indicates that most perinates died prior to or shortly after birth, experienced adverse conditions in utero, and most had in utero infections. Findings from both the live and dead animal studies confirmed low reproductive success from heavily oiled estuaries when compared with other populations. Follow-up studies are planned to begin in the summer of 2016 to better understand the potential recovery of dolphins in Barataria Bay and, by extension, other Gulf coastal regions impacted by the spill.


We greatly appreciate the efforts of the multi-institutional field teams involved in the acquisition of data. In particular, we thank Veronica Cendejas for technical and logistical assistance with ultrasound exams. This work was part of the Deepwater Horizon NRDA being conducted cooperatively among NOAA, other Federal and State Trustees and BP PLC.

* Presenting author

Literature Cited

1.  NOAA. Injury to natural resources. Deepwater Horizon Oil Spill: Draft Programmatic Damage Assessment and Restoration Plan and Draft Programmatic Environmental Impact Statement, National Oceanic and Atmospheric Administration. http://www.gulfspillrestoration.noaa.gov/wp-content/uploads/Chapter-4_Injury-to-Natural-Resources1.pdf. 2015. Accessed November 11, 2015.

2.  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 Tech. 2014;48:93–103.

3.  Venn-Watson S, Colegrove KM, Litz J, Kinsel M, Terio K, Saliki J, Fire S, Carmichael R, Chevis C, Hatchett W, Pitchford J, Tumlin M, Field C, Smith S, Ewing R, Fauquier D, Lovewell G, Whitehead H, Rotstein D, McFee W, Fougeres E, Rowles T. Adrenal gland and lung lesions in Gulf of Mexico common bottlenose dolphins (Tursiops truncatus) found dead following the Deepwater Horizon oil spill. PLoS One. 2015;10(5):e0126538.

4.  Lane SM, Smith CR, Mitchell J, Balmer BC, Barry KP, McDonald T, Mori CS, Rosel PE, Rowles TK, Speakman TR, Townsend FI, Tumlin MC, Wells RS, Zolman ES, Schwacke LH. Reproductive outcome and survival of common bottlenose dolphins sampled in Barataria Bay, Louisiana, USA, following the Deepwater Horizon oil spill. Proc Biol Sci. 2015;282(1818):20151944.

5.  Colegrove KM, Venn-Watson S, Litz J, Kinsel MK, Terio KA, Fougeres E, Ewing R, Pabst DA, McLellan WA, Raverty S, Saliki J, Fire S, Rappucci G, Bowen-Stevens S, Nobel L, Costidis A, Barbieri M, Field C, Smith S, Carmichael RH, Chevis C, Hatchett W, Shannon D, Tumlin M, Lovewell G, McFee W, Rowles TK. 2015. Fetal distress and in utero Brucella pneumonia in perinatal bottlenose dolphins (Tursiops truncatus) during the Northern Gulf of Mexico unusual mortality event: 2010 through 2013. Dis Aquat Organ. doi: 10.3354/dao02969.


Speaker Information
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Cynthia R. Smith, DVM
National Marine Mammal Foundation
San Diego, CA, USA

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