Mercury Exposure is Associated with Negative Effects on Turtle Reproduction

Mercury (Hg), a ubiquitous and highly toxic bioaccumulative contaminant, can maternally transfer and elicit deleterious effects on adult reproduction and offspring phenotype in fish, amphibians, and birds. However, the effects of Hg on reproduction remain largely unstudied in reptiles. We evaluated the consequences of maternally transferred Hg on a long-lived aquatic omnivore, the common snapping turtle (Chelydra serpentina). We collected eggs and tissues from gravid female turtles along a broad Hg contamination gradient in a river in central Virginia. We incubated eggs in the laboratory, quantified embryonic mortality, infertility, and hatching success of each clutch, and assessed all hatchlings and dead embryos for gross morphological malformations. As predicted, Hg concentrations in eggs were strongly and positively correlated with Hg levels in female tissues. We found that Hg in eggs was negatively correlated with hatching success, and this effect was driven by both increased egg infertility and embryonic mortality. In comparison to previous effect-based studies on other amniotes, our findings suggest that C. serpentina may be more resilient to Hg exposure and perhaps better suited for long-term monitoring of bioavailability of Hg than as indicators of adverse effects.