10.1021/es302369h.s001 Ruth H. Carmichael Ruth H. Carmichael Amanda L. Jones Amanda L. Jones Heather K. Patterson Heather K. Patterson William C. Walton William C. Walton Alberto Pérez-Huerta Alberto Pérez-Huerta Edward B. Overton Edward B. Overton Meghan Dailey Meghan Dailey Kristine L. Willett Kristine L. Willett Assimilation of Oil-Derived Elements by Oysters Due to the Deepwater Horizon Oil Spill American Chemical Society 2016 Average δ13 C δ15 N values Deepwater Horizon Oil Spill oyster adductor muscle ratio Deepwater Horizon Oil SpillDuring SPM assimilation diet oil materials DWHOS 2016-02-20 04:52:21 Journal contribution https://acs.figshare.com/articles/journal_contribution/Assimilation_of_Oil_Derived_Elements_by_Oysters_Due_to_the_Deepwater_Horizon_Oil_Spill/2464312 During and after the Deepwater Horizon Oil Spill (DWHOS), oysters (<i>Crassostrea virginica</i>) were exposed to oil and susceptible to incidental consumption of surface and subsurface oil materials. We determined the contribution of oil materials from the DWHOS to diet of oysters by comparing carbon (C) and nitrogen (N) stable isotope ratios in oyster shell to ratios in suspended particulate matter (SPM) and in fresh and weathered oil. Average δ<sup>13</sup>C and δ<sup>15</sup>N values in oyster shell (−21 ± 1‰ and 9–11‰, respectively) were consistent with consumption of naturally available SPM as opposed to values in oil (−27 ± 0.2‰, 1.6 ± 0.4‰). Stable isotope ratios in oyster adductor muscle were similar to shell for δ<sup>15</sup>N but not δ<sup>13</sup>C, suggesting either a recent shift in diet composition or differential assimilation of C between tissue types. We found no evidence of assimilation of oil-derived C and N and, therefore, no evidence of an oyster-based conduit to higher trophic levels. Trace elements in shell were inconclusive to corroborate oil exposure. These findings are not an indication that oysters were not exposed to oil; rather they imply oysters either did not consume oil-derived materials or consumed too little to be detectable compared to natural diet.