ESR 33:69-82 (2017)  -  DOI: https://doi.org/10.3354/esr00771

Density and exposure of surface-pelagic juvenile sea turtles to Deepwater Horizon oil

Trent L. McDonald1,*, Barbara A. Schroeder2, Brian A. Stacy2, Bryan P. Wallace3,4, Leigh Ann Starcevich1, Jonathan Gorham5, Mandy C. Tumlin6, Dave Cacela3, Matthew Rissing3, Danya B. McLamb7, Eric Ruder7, Blair E. Witherington

1Western EcoSystems Technology, Inc., Laramie, WY 82070, USA
2Office of Protected Resources, NOAA Fisheries, Silver Spring, MD 20910, USA
3Abt Associates, Inc., Boulder, CO 80302, USA
4Nicholas School of the Environment, Duke University Marine Lab, Beaufort, NC 28516, USA
5In-water Research Group, Jensen Beach, FL 34957, USA
6Louisiana Department of Wildlife and Fisheries, Baton Rouge, LA 70808, USA
7Industrial Economics, Inc., Cambridge, MA 02140, USA
8Disney’s Animals, Science and Environment, Lake Buena Vista, FL 32830, USA
*Corresponding author:

ABSTRACT: The 2010 Deepwater Horizon (DWH) oil spill posed a severe threat to surface-pelagic sea turtles because the surface convergence zones, which provide vital habitat by aggregating pelagic Sargassum and other floating material, also aggregated floating oil. Following the DWH spill, turtle rescue operations between 17 May and 9 September 2010 documented 937 juvenile sea turtles in the spill area and examined 574 captured turtles. Of the captured turtles, 81% were visibly oiled. Transect searches in convergence zones found Kemp’s ridleys (51% of individuals), green turtles (37%), loggerheads (7%), hawksbills (2%), and unidentified sea turtles (2%). Line-transect methods estimated the density of all surface-pelagic sea turtles in surface convergence zones to be 3.32 km-2 (95% CI = 2.82–3.88), and the density of heavily oiled turtles to be 0.24 km-2 (95% CI = 0.15–0.39). Turtle densities and the areal extent of heavy oiling probability were used to estimate total number of turtles exposed to DWH oil. We estimate approximately 402000 surface-pelagic sea turtles were exposed, and of those, 54800 were likely to have been heavily oiled. Our estimates formed the basis of surface-pelagic juvenile sea turtle mortality estimates included in the DWH natural resource damage assessment.


KEY WORDS: Oil exposure · Gulf of Mexico · Surface-pelagic · Oiling · Loggerhead sea turtle · Kemp’s ridley sea turtle · Green sea turtle · Hawksbill sea turtle · Deepwater Horizon oil spill


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Cite this article as: McDonald TL, Schroeder BA, Stacy BA, Wallace BP and others (2017) Density and exposure of surface-pelagic juvenile sea turtles to Deepwater Horizon oil. Endang Species Res 33:69-82. https://doi.org/10.3354/esr00771

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