Intraspecific variation in mercury, δ 15 N, and δ 13 C among three Adélie Penguin (Pygoscelis adeliae) populations in the northern Antarctic Peninsula region

Abstract

Mercury (Hg) is a pervasive environmental contaminant that accumulates in the organs and tissues of seabirds at concentrations capable of causing acute or long-term adverse health effects. In this study, Hg concentrations in Adélie Penguin (Pygoscelis adeliae) egg membranes and chick feathers served as a proxy for Hg bioavailability in the marine environment surrounding the northern Antarctic Peninsula. Stable isotopes were measured in conjunction with Hg to infer information regarding feeding habits (δ15N, diet/trophic level; δ13C, foraging habitat). Hg concentrations were low relative to toxicity benchmark values associated with adverse health effects in birds and ranged between 0.006 ? 0.080 µg g-1 dry weight (n = 65) in egg membranes and 0.140 ? 1.05 µg g-1 fresh weight (n= 38) in feathers. Egg membrane δ15N signatures suggested females from different breeding colonies had similar diets consisting of lower and higher trophic prey prior to arrival to breeding grounds. In contrast, δ15N signatures in feathers indicated chick diet varied by colony. Hg concentrations demonstrated significant positive relationships with δ15N providing support for the hypothesis of Hg biomagnification up the food chain. δ13C signatures in both tissue types provided evidence of foraging habitat segregation among populations. The differences in Hg exposure and foraging ecology suggest that each colony has localized foraging behaviors by breeding adults that warrant additional investigation.