John Wiley & Sons, Ltd.

Habitat‐specific foraging and sex determine mercury concentations in sympatric benthic and limnetic ecotypes of threespine stickleback

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Mercury (Hg) is a widespread environmental contaminant known for the neurotoxicity of the methylated forms, especially monomethyl mercury, which bioaccumulates and biomagnifies in aquatic food webs. Mercury bioaccumulation and biomagnification rates are known to vary among species utilizing different food webs (benthic versus limnetic) within and between systems. We assessed if carbon and nitrogen stable isotope values and total Hg (THg) concentrations differed between sympatric benthic and limnetic ecotypes and sexes of threespine stickleback fish (Gasterosteus aculeatus) from Benka Lake, Alaska (USA). The mean THg concentration in the limnetic ecotype was significantly higher (26 mg/kg dw; 16.1%) than that of the benthic ecotype. Trophic position and percent benthic carbon utilized were both important determinants of THg concentration; however, in females the two variables were of approximately equal importance whereas in males trophic position clearly explained more of the variance than percent benthic carbon. Additionally, strong sex effects (45 mg/kg dw; 29.4%) were observed in both ecotypes with female fish having lower THg concentrations than males. These results indicate that trophic ecology and sex are both important determinants of Hg contamination even within a single species and lake, and likely play a role in governing Hg concentrations in higher trophic levels. Environ. Toxicol. Chem. © 2013 SETAC

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