Data tables in support of manuscript "δ13C and δ15N in the endangered Kemp's ridley sea turtle lepidochelys kempii after the Deepwater Horizon oil spill"
Dates
Publication Date
2017-04-18
Start Date
2010-01-01
End Date
2012-12-31
Citation
National Park Service, 2016, Data tables in support of manuscript "δ13C and δ15N in the endangered Kemp's ridley sea turtle lepidochelys kempii after the Deepwater Horizon oil spill": U.S. Geological Survey data release, http://dx.doi.org/10.5066/F70C4SXJ.
Summary
Following an explosion at the Deepwater Horizon drilling rig on April 20, 2010, MC252 an estimated 3.19 million barrels of oil leaked into the Northern Gulf of Mexico over 87 days. The endangered Kemp's ridley sea turtle (Lepidochelys kempii [Lk]) has a long established record of using the area near the well as primary foraging grounds. Resulting short- and long-term negative impacts of the oil spill on sea turtles could induce changes in the health and fitness of the Lk population. MC252 oil is known to have entered the foraging areas. Consequently, stable carbon and nitrogen isotope signatures from MC252 oil should be reflected in the food web and in the tissues of organisms such as sea turtles. We measured carbon and nitrogen isosope [...]
Summary
Following an explosion at the Deepwater Horizon drilling rig on April 20, 2010, MC252 an estimated 3.19 million barrels of oil leaked into the Northern Gulf of Mexico over 87 days. The endangered Kemp's ridley sea turtle (Lepidochelys kempii [Lk]) has a long established record of using the area near the well as primary foraging grounds. Resulting short- and long-term negative impacts of the oil spill on sea turtles could induce changes in the health and fitness of the Lk population. MC252 oil is known to have entered the foraging areas. Consequently, stable carbon and nitrogen isotope signatures from MC252 oil should be reflected in the food web and in the tissues of organisms such as sea turtles. We measured carbon and nitrogen isosope ratios of satellite-tagged turtles to 1) assess changes in foraging strategies of nesting Lk sampled in 2010 (the year of the spill) and two subsequent post-spill years; and 2) estimate the proportion of females that were within the area affected by the oil spill, the latter via discriminant analysis. Scute samples were collected using a biopsy punch from turtles nesting at a long-term study site on the Lower Texas Coast (Padre Island National Seashore) and on the Upper Texas Coast (Galveston Island to Surfside Beach). Turtles included in this study were sampled only once. δ13C values in samples obtained from turtles nesting in 2011 and 2012 were significantly depleted (F3,96=4.76, p=0.004 ) compared to 2010 samples. In contrast, there were no significant differences in δ15N among years. The depleted carbon values correlate with the depleted carbon values of MC252 oil. The distinctive isotope values of the satellite tagged females provided data with which to identify turtles that were inside the oiled area
Stable isotopes of carbon (C) and nitrogen (N) incorporated in the scutes of sea turtles (inert tissue with continuous growth) provide a history of foraging and habitat use when serial samples of the scute are analyzed (Reich et al. 2007). The oldest dietary record is retained in the outermost layer of scute and each successive layer (0.05 mm) reveals more recent diet and habitat use (Reich et al. 2007, 2008; Vander Zanden et al. 2010). Therefore, if the turtles were exposed to oil after the spill, it may be detected in the recent layers of scute using stable isotopes of carbon and nitrogen. Here, we address three questions: 1) were nesting females of 2010 exposed to the oil in their foraging grounds? 2) Is the signature of the oil still present in the foraging area in subsequent years after the spill? 3) What is the proportion of females that were affected by the oil spill? To answer these questions, we analyzed scute samples of female turtles from three consecutive years, 2010, 2011 and 2012.
