a b s t r a c tIn sea turtles, parental investment is limited to the nutrients and energy invested in eggs that will support embryonic development. Leatherback females have the largest clutches with the biggest eggs of the sea turtles and the highest reproductive output in reptiles. The migration between foraging sites and nesting beaches also represents high energy expenditure. The toxicokinetic of pollutants in the tissues is thus expected to vary during those periods but there is a lack of information in reptiles. Concentrations of essential (Copper, Zinc, Selenium) and non-essentials elements (Cadmium, Lead, Mercury) were determined in blood (n = 78) and eggs (n = 76) of 46 free-ranging leatherback females collected in French Guiana. Maternal transfer to eggs and relationships between blood and eggs concentrations during the nesting season were investigated. All trace elements were detectable in both tissues. Levels of toxic metals were lower than essential elements likely due to the high pelagic nature of leatherbacks that seems to limit exposure to toxic elements. Significant relationships between blood and egg concentrations were observed for Se and Cd. Se could have an important role in embryonic development of leatherback turtles and Cd transfer could be linked to similar carrier proteins as Se. Finally, as multiple clutches were sampled from each female, trends in trace elements were investigated along the nesting season. No change was observed in eggs but changes were recorded in blood concentrations of Cu. Cu level decreased while blood Pb levels increased through the nesting season. The high demand on the body during the breeding season seems to affect blood Cu concentrations. Calcium requirement for egg production with concomitant Pb mobilization could explain the increase in blood Pb concentrations along the nesting season.
BackgroundThe leatherback turtle (Dermochelys coriacea) has undergone a dramatic decline over the last 25 years, and this is believed to be primarily the result of mortality associated with fisheries bycatch followed by egg and nesting female harvest. Atlantic leatherback turtles undertake long migrations across ocean basins from subtropical and tropical nesting beaches to productive frontal areas. Migration between two nesting seasons can last 2 or 3 years, a time period termed the remigration interval (RI). Recent satellite transmitter data revealed that Atlantic leatherbacks follow two major dispersion patterns after nesting season, through the North Gulf Stream area or more eastward across the North Equatorial Current. However, information on the whole RI is lacking, precluding the accurate identification of feeding areas where conservation measures may need to be applied.Methodology/Principal FindingsUsing stable isotopes as dietary tracers we determined the characteristics of feeding grounds of leatherback females nesting in French Guiana. During migration, 3-year RI females differed from 2-year RI females in their isotope values, implying differences in their choice of feeding habitats (offshore vs. more coastal) and foraging latitude (North Atlantic vs. West African coasts, respectively). Egg-yolk and blood isotope values are correlated in nesting females, indicating that egg analysis is a useful tool for assessing isotope values in these turtles, including adults when not available.Conclusions/SignificanceOur results complement previous data on turtle movements during the first year following the nesting season, integrating the diet consumed during the year before nesting. We suggest that the French Guiana leatherback population segregates into two distinct isotopic groupings, and highlight the urgent need to determine the feeding habitats of the turtle in the Atlantic in order to protect this species from incidental take by commercial fisheries. Our results also emphasize the use of eggs, a less-invasive sampling material than blood, to assess isotopic data and feeding habits for adult female leatherbacks.
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