Melania C. Lopez-Castro Donna J. Shaver Claire Iseton Kristen M. Hart Michael J. Hooper Christopher J. Schmitt Kimberly J. Reich 2017 <p><span>The </span><i>Deepwater Horizon</i><span> explosion in April 2010 and subsequent oil spill released 3.19 × 10</span>⁶<span> barrels (5.07 × 10</span>⁸<span> L) of MC252 crude oil into important foraging areas of the endangered Kemp’s ridley sea turtle </span><i>Lepidochelys kempii</i><span> (</span><i>Lk</i><span>) in the northern Gulf of Mexico (GoM). We measured δ</span>¹³<span>C and δ</span>¹⁵<span>N in scute biopsy samples from 33 </span><i>Lk</i><span> nesting in Texas during 2010–-12. Of these, 27 were equipped with satellite transmitters and were tracked to traditional foraging areas in the northern GoM after the spill. Differences in δ</span>¹³<span>C between the oldest and newest scute layers from 2010 nesters were not significantly different, but δ</span>¹³<span>C in the newest layers from 2011 and 2012 nesters was significantly lower compared to 2010. δ</span>¹⁵<span>N differences were not statistically significant. Collectively, the stable isotope and tracking data indicate that the lower δ</span>¹³<span>C values reflect the incorporation of oil rather than changes in diet or foraging area. Discriminant analysis indicated that 51.5% of the turtles sampled had isotope signatures indicating oil exposure. Growth of the </span><i>Lk</i><span> population slowed in the years following the spill. The involvement of oil exposure in recent population trends is unknown, but long-term effects may not be evident for many years. Our results indicate that C isotope signatures in scutes may be useful biomarkers of sea turtle exposure to oil.</span></p> application/pdf 10.3354/esr00819 en Inter-Research δ13C and d15N in the endangered Kemp’s ridley sea turtle Lepidochelys kempii after the Deepwater Horizon oil spill article