An examination of mercury concentrations in eggshells of the common snapping turtle (Chelydra serpentina) in Nova Scotia, Canada

Mercury (Hg) is a potentially toxic metal that has bioaccumulating and biomagnifying properties. In egg laying animals, it can be transferred from an adult female to offspring. However, in turtles, the inter-and-intra-nest variation of Hg concentrations remains unknown. We investigated the concentration of Hg in preyed-upon Common Snapping Turtles (Chelydra serpentina) eggshells. The variability in Hg contamination between and within each nest was assessed. In June 2021, 368 eggshells left behind by predators were sampled from 14 nests, from three different sites in southwest Nova Scotia. Ten eggshells were randomly selected from each nest for analysis. We found no correlation between estimated number of eggs in a nest and average nest Hg concentration. Significant inter-nest variation (Hg ranging from 12.0 ± 3.85 to 172.3 ± 43.9 µg/kg) and intra-nest variability may indicate maternal transfer. The collection of the shells of freshly preyed- upon eggs is a useful non-destructive sampling technique to maintain sustainable turtle populations. Our results demonstrate the need for further investigation into the impact of Hg on temperate, freshwater turtle reproduction. Keywords: mercury concentration, maternal transfer, common snapping turtle, eggshells