Non-lethal nail sampling as an indicator of spatial and demographic patterns of mercury exposure in southeastern U.S. sea turtles

Abstract

The global distribution of mercury (Hg) has led to widespread deleterious effects for wildlife and their health. Sea turtle populations may be adversely affected by this contaminant, and this may particularly be true in areas such as the Gulf of Mexico, Florida Bay, and Florida Everglades due to anthropogenic activity. The implementation of a non-lethal sampling method, such as clippings from nails, may be beneficial for monitoring this contaminant in sea turtle individuals and their populations. We assess the viability of nails as a non-lethal sampling alternative and explore potential drivers of differences in Hg exposure among sea turtles in the southeastern U.S. region. To better understand the relationship between total Hg (THg) concentration in nails and internal concentrations, we examined the relationship between nail and blood THg and methylmercury (MeHg) in 42 individuals consisting of Loggerhead (Caretta caretta) and Green (Chelonia mydas) sea turtle species, sampled at 4 nesting beaches located around the southeastern U.S. during their breeding season. Linear regressions demonstrated that nail and blood was strongly correlated in both THg and MeHg, further supporting this as a viable sampling method. We found that mercury exposure was influenced by species, but not by body size. Foraging locations of sea turtle species were shown to significantly differ, but we were unable to establish differences between individual locations. Finally, sea turtles in this region compared were found to fall in the lower range of values compared to global Hg averages. Overall, our results are the first to suggest that this non-lethal sampling method as a suitable indicator for internal Hg levels in sea turtles.