First report of metallic elements in loggerhead and leatherback turtle eggs from the Indian Ocean

Abstract

Bio-monitoring of pollutants in long-lived animals such as sea turtles is an important tool in ecotoxicology. We present the first report on metallic elements in sea turtle eggs from the Indian Ocean. Eggs of the leatherback and loggerhead turtle that breed on the Indian Ocean coast of South Africa were analysed for 30 elements. The eggshells and egg contents of the loggerhead turtle, the smaller of the two species, had higher or significantly higher concentrations than leatherbacks, except for strontium - the reason is unknown. Elemental concentrations in eggshells and contents were the same or lower compared with other studies. The differences in concentrations in the egg contents and eggshells between the two species are likely due to different trophic levels, migration patterns, life histories, age, and growth, as well as differences in pollution sources and the uptake, retention and elimination characteristics of the different elements by the different species. We found no congruence between patterns in eggshells and corresponding egg contents, for both species. However, eggshells and egg contents showed congruence between species. The lack of congruence between eggshells and contents within each species precludes using eggshell concentrations as a proxy for egg content concentrations. Copper, strontium, and selenium occurred at concentrations higher than available toxic reverence values. Further research is warranted, including the analyses of POPs, as well as possible deme discrimination based on compositional pattern differences. Turtles serve as 'active samplers' returning to the same location to breed-something that is not practical with marine mammals or elasmobranchs.

Keywords: Climate change; Deme discrimination; Endocrine disruption; Heavy metal; Reptile; Toxic reference value.