Maternal transfer of trace elements in leatherback turtles (Dermochelys coriacea) of French Guiana

In 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 seasonwere investigated. All trace elementswere 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 clutcheswere sampled from each female, trends in trace elements were investigated along the nesting season. No change was observed in eggs but changeswere 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

Phenology of marine turtle nesting revealed by statistical model of the nesting season

BACKGROUND: Marine turtles deposit their eggs on tropical or subtropical beaches during discrete nesting seasons that span several months. The number and distribution of nests laid during a nesting season provide vital information on various aspects of marine turtle ecology and conservation. RESULTS: In the case of leatherback sea turtles nesting in French Guiana, we developed a mathematical model to explore the phenology of their nesting season, derived from an incomplete nest count dataset. We detected 3 primary components in the nest distribution of leatherbacks: an overall shape that corresponds to the arrival and departure of leatherback females in the Guianas region, a sinusoidal pattern with a period of approximately 10 days that is related to physiological constraints of nesting female leatherbacks, and a sinusoidal pattern with a period of approximately 15 days that likely reflects the influence of spring high tides on nesting female turtles. CONCLUSION: The model proposed here offers a variety of uses for both marine turtles and also other taxa when individuals are observed in a particular location for only part of the year

Isotope Analysis Reveals Foraging Area Dichotomy for Atlantic Leatherback Turtles

Background: The 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 Findings: Using 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/Significance: Our 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

Etude des facteurs écologiques et écotoxicologiques impliqués dans la réussite d’incubation chez la tortue luth, Dermochelys coriacea, de Guyane Française

Leatherback turtles, Dermochelys coriacea, have relatively low hatching success in comparison to other marine turtle species. This low hatching rate is largely a result of high embryonic mortality rather than infertility, but the specific causes remain unknown. Leatherbacks are vulnerable to excessive adult mortality (resulting in population decline) because they are long-lived species. However, low hatching success and corresponding low juvenile recruitment could also result in long term declines of leatherbacks. On the Yalimapo beach, in French Guiana, hatching success is lower for this species than on other nesting sites, emphasising the problem of recruitment for the population. Understanding the causes of low hatching success is therefore an important conservation step towards preventing extinction in this population. During my thesis, I investigated the role of ecological (predation and nest site location) and ecotoxicological factors (blood and egg contamination by trace elements and organochlorine compounds) on the hatching success of leatherback nests. Firstly, nest location was shown to have an important effect on predation and inundation rate that decreased hatching success. Secondly, a maternal transfer of contaminants from females to their eggs was confirmed, raising the issue of the deleterious effects of environmental contaminants on embryos development, a developmental stage very sensitive to contaminants. Dose-effect relationships between contaminants and hatching success need to be assessed to establish the risk of environmental pollution for leatherback reproduction. Moreover, the use of stable isotope analysis for females differing in the number of years between two reproductive seasons revealed that they used different feeding areas. These feeding grounds differed in their geographical location, but also in the quality of the available prey in terms of their level of contamination by environmental pollutants, highlighting the issue of adult contamination. This thesis confirmed the importance of ecological factors for hatching rate and highlighted the existence of ecotoxicological factors, which have not yet been studied for the leatherback turtle

Maternal transfer of chlorinated contaminants in the leatherback turtles, Dermochelys coriacea, nesting in French Guiana

We examined the maternal transfer of organochlorine contaminants (OCs), pesticides (DDTS and HCHs) 26 and polychlorinated biphenyls (PCBs), and the temporal variation of blood and eggs concentrations from 27 38 leatherback turtles (Dermochelys coriacea) nesting in French Guiana. PCBs were found to be the dom- 28 inant OCs with respective mean concentrations of 55.14 ng g 1 lipid-mass for egg and 1.26 ng mL 1 wet- 29 mass for blood. OC concentrations were lower than concentrations measured in other marine turtles 30 which might be due to the lower trophic position (diet based on gelatinous zooplankton) and to the loca- 31 tion of their foraging and nesting grounds. All OCs detected in leatherback blood were detected in eggs, 32 suggesting a maternal transfer of OCs. This transfer was shown to depend on female blood concentration 33 for RDDTs and for the most prevalent PCB congeners, since significant relationships were found between 34 paired blood–egg concentrations. During the nesting season, OC concentrations in eggs and the percent- 35 age of lipid in eggs were found to decline in successive clutches, highlighting a process of offloading from 36 females to their eggs and a decreasing investment of lipid from females into their clutches. OCs in eggs 37 tended to be higher in females spending 3 years in the foraging grounds between two nesting seasons 38 than in those spending 2 years, suggesting an impact of time spacing two breeding seasons, called remi- 39 gration interval, and of location of the foraging grounds

Etude des facteurs écologiques et écotoxicologiques impliqués dans la réussite d incubation chez la tortue luth Dermochelys coriacea de Guyane Française

La tortue luth, Dermochelys coriacea, présente une réussite d incubation relativement faible en comparaison aux autres espèces de tortues marines. Ce faible taux a été attribué à une mortalité embryonnaire accrue plutôt qu à une infertilité, mais les causes spécifiques de cette mortalité restent peu connues. Les espèces longévives, comme la luth, sont plutôt vulnérables à une mortalité adulte élevée, qui peut entraîner d importants déclins des effectifs. Cependant, sur le long terme, un faible recrutement des juvéniles peut aussi considérablement jouer sur la dynamique d une population. A Yalimapo, en Guyane Française, la réussite d incubation est encore plus faible que sur les autres sites de ponte de l espèce ce qui pose réellement le problème du recrutement des juvéniles et du renouvellement des effectifs de cette population. Comprendre les causes de ce faible succès de reproduction est donc primordial pour assurer la conservation de cette espèce. Au cours de cette thèse, je me suis intéressée à l effet de certains facteurs écologiques (prédation, place du nid sur la plage) et écotoxicologiques (niveaux de contamination dans le sang et les œufs en éléments traces métalliques et composés organochlorés) sur la réussite d incubation des nids. Il est apparu en premier lieu que le choix du site de ponte par la femelle avait un impact direct sur la réussite d incubation, en jouant sur la densité de prédation et les risques d inondation et d érosion des nids. Dans un second temps, la présence de contaminants dans les œufs a confirmé l existence d un transfert maternel de la femelle vers ses œufs qui expose les embryons à une source de pollution dès les premiers stades de développement, souvent les plus sensibles. Les relations doses effets restent à évaluer pour déterminer le risque encouru par les tortues face au problème de la pollution environnementale. De plus, l utilisation des isotopes stables a permis de détecter que des femelles différant dans le nombre d années séparant deux saisons de reproduction, présentaient également des différences dans leurs sites d alimentation (situation géographique, qualité environnementale du site) soulevant le problème de la contamination des adultes par ingestion de leurs proies. Cette thèse a permis de confirmer l importance des facteurs écologiques dans la réussite d incubation et de souligner l existence des facteurs écotoxicologiques qui, jusqu à ce jour, n avaient pas été envisagés chez la tortue luth.Leatherback turtles, Dermochelys coriacea, have relatively low hatching success in comparison to other marine turtle s species. This low hatching rate is largely a result of high embryonic mortality rather than infertility, but the specific cause remains unknown. Long lived species such as leatherbacks are more vulnerable to excessive adult mortality that results in dramatic population decline. However, low hatching success could result in long term declines caused by a recruitment of juveniles too low. Leatherbacks populations have already suffered from dramatic decline. On the Yalimapo beach, in French Guiana, hatching success is lower than on other nesting sites for this species, stressing the problem of recruitment of the population. Therefore, understanding causes of low hatching success would be an important conservation step towards preventing extinction in this species. During my thesis, I investigated the role of ecological (predation and nest site location) and ecotoxicological factors (blood and egg contamination in trace elements and organochlorine compounds) on the hatching success of nests. First, nest location has been shown to have an important effect on predation and inundation rate that decreased hatching success. Second, a maternal transfer of contaminants from females to their eggs was assessed, raising the question of deleterious effects of environmental contaminants on embryos development, a very sensitive stage to contaminants. Dose-effects relationships between contaminants and hatching success need to be assessed to establish risk of environmental pollution for leatherbacks. The use of stable isotope analysis in females differing in the number of years between two reproductive seasons made possible to highlight different feeding areas used by those females. These feeding grounds differed in their geographical location, but also in the quality of the preys available in terms of level of contamination by environmental pollutants raising the question of adult contamination. This thesis confirmed the importance of ecological factors for hatching rate and highlighted the existence of ecotoxicological factors, which have not been studied yet for the leatherback turtle.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF