Blood levels of metallic trace elements are influenced by sex, age and habitat in the European pond turtle (Emys orbicularis).

Metallic trace elements (MTEs) constitute a major source of chemical pollution and represent a threat to aquatic ecosystems and organisms. Important variation in contamination may exist at a local scale in relation to the environment (hydrosystem, trophic ressources) and individual traits (age, sex). Heretofore, the factors influencing MTEs exposure of freshwater reptiles in temperate regions are not fully understood. Freshwater turtles have a relatively high trophic position and a long lifespan, thus being potentially highly exposed due to bioaccumulation and bioamplification processes. We investigated MTE blood concentrations from two populations of the European pond turtle (Emys orbicularis) in the Camargue wetland (France). These populations, monitored since 1997, differ in their habitat and exposure (irrigation versus drainage canal). In this study, we detected 7 MTEs (Cu, Fe, Hg, Mn, Pb, Se, and Zn) which levels depended on site and individual characteristics. Hg was positively related to body size and age, indicating an increase of exposure in older individuals. We found differences between males and females with the interaction with body size for Pb and Se and with age for Pb. Nitrogen and carbon stable isotopes varied only marginally between individuals and were poorly associated with MTEs concentrations, showing that trophic position might not explain MTEs contamination for these populations. At the individual level, Hg, Pb, and Se blood values were repeatable over years. Further studies should concentrate on potential ecophysiological effects to such exposure, especially since we recently evidenced that these populations of E. orbicularis are highly exposed to organic contaminants, which can lead to synergistic effects.