Mercury bioaccumulation in offshore reef species from waters of the southeastern US
Sinkus, Wiley Nicholas
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Total mercury (Hg) concentrations and stable isotopic ratios of nitrogen (δ<sup>15</sup>N) and carbon (δ<sup>13</sup>C) were measured to assess differences in Hg bioaccumulation in six predatory fish species (<i>Mycteroperca microlepis</i>, <i>M. phenax</i>, <i>Epinephelus morio</i>, <i>Lutjanus campechanus</i>, <i>Caulolatilus microps</i>, and <i>Seriola dumerili</i>) of high commercial and recreational importance in Atlantic waters of the Southeastern US (ASEUS), Strong positive relationships existed between Hg and length, weight, and age, for all of the species except <i>C. microps</i> and <i>S. dumerili</i>. Intraspecific Hg concentrations also strongly correlated with a proxy for relative trophic position (δ<sup>15</sup>N), for all species except <i>E. morio</i> and a proxy for food source (δ<sup>13</sup>C) for only <i>M. phenax</i>, <i>L. campechanus</i>, and <i>S. dumerili</i>. Comparisons of mean δ<sup>15</sup>N and δ<sup>13</sup>C between species and their impact on mean Hg concentration were inconclusive. This study is the first to report Hg concentrations for <i>C. microps</i>, revealing moderately high mean concentrations (0.38 ± 0.17 ppm). Mercury accumulation rates varied between species, ranging from 0.02 ppm yr-1 weight wet (ww) for <i>C. microps</i> to 0.05 ppm yr<sup>-1</sup> ww for <i>M. microlepis</i>. Measured species had moderate Hg concentrations for predatory fishes, with 59% of all samples and mean concentrations of <i>M. microlepis</i>,<i> M. phenax</i>, and <i>L. campechanus</i> below 0.30 ppm (US Environmental Protection Agency screening level). Mercury accumulation was significantly different between sexes for <i> L. campechanus</i>, and the hermaphroditic species <i>M. microlepis</i>, <i>M. phenax</i>, and <i>E. morio</i>. The current study provides additional data for an under-sampled region (ASEUS), explores how feeding ecology impacts Hg uptake in commonly co-occurring fishes, and raises questions of the importance of sex and reproduction in Hg accumulation for marine fishes.