Selenium (Se) is a bioaccumulative constituent of coal fly-ash that can disrupt reproduction of oviparous wildlife. In food webs, the greatest enrichment of Se occurs at the lowest trophic levels, making it readily bioavailable to higher consumers. However, subsequent enrichment at higher trophic levels is less pronounced, leading to mixed tendencies for Se to biomagnify. We used stable isotopes ((1)(5)N and (13)C) in claws to infer relative trophic positions and relative carbon sources, respectively, of seven turtle species near the site of a recently-remediated coal fly-ash spill. We then tested whether Se concentrations differed with relative trophic position or relative carbon source. We did not observe a strong relationship between δ(15)N and Se concentration. Instead, selenium concentrations decreased with increasing δ(13)C among species. Therefore, in an assemblage of closely-related aquatic vertebrates, relative carbon source was a better predictor of Se bioaccumulation than was relative trophic position.