Why are hatching and emergence success low? Mercury and selenium concentrations in nesting leatherback sea turtles (Dermochelys coriacea) and their young in Florida

Leatherback sea turtles (Dermochelys coriacea) have low hatching and emergence success compared to other sea turtle species. Postmortem examinations of hatchlings showed degeneration of heart and skeletal muscle that was similar to that found in other neonates with selenium deficient mothers. Selenium deficiency can result from elevated concentrations of bodily mercury. Ingested mercury is detoxified by the liver through mercury-selenium compound formation. In animals persistently exposed to mercury, the liver's ability to detoxify this element may decrease, especially if dietary selenium is insufficient. We measured mercury and selenium concentrations in nesting female leatherbacks and their hatchlings from Florida and compared the levels to hatching and emergence success. Both liver selenium and the liver selenium-to-mercury ratio positively correlated with leatherback hatching and emergence success. This study provides the first evidence for the roles of mercury and selenium in explaining low reproductive success in a globally imperiled species, the leatherback sea turtle.

► Documented mercury (Hg) and selenium (Se) levels in nesting leatherback turtles and hatchlings. ► Nesting leatherbacks pass on higher levels of Se (essential) than Hg (non-essential) to offspring. ► Hatchling liver Se concentrations were positively correlated with hatching/emergence success. ► Hatchling liver Se-to-Hg ratio was positively correlated with hatching/emergence success. ► First correlative evidence relating decreased reproductive success to Hg and Se in leatherbacks.