Identifying oceanic foraging grounds of sea turtles in the Atlantic using lead isotopes
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Many species of marine organisms go through ontogenetic shifts that occur in unknown or inaccessible locations. Finding these areas is crucial to understand connectivity and resilience of populations, both of which have conservation implications. When extrinsic markers are not suitable to track organisms, intrinsic markers can be useful to infer the location of inaccessible areas where these cryptic stages occur. Our study focuses on the location of oceanic foraging areas of the cryptic early juvenile stage of green turtles, Chelonia mydas, in the Atlantic. Due to the small size of hatchlings, the use of telemetry is limited to short periods of time and small spatial ranges, which do not allow determining the location of oceanic foraging areas. We used lead (Pb) stable isotopes to determine the possible location of oceanic foraging areas of small green turtles in the Atlantic Ocean. Pb stable isotope ratios in the scute tissue deposited when turtles were in the oceanic habitat were compared to ratios of major sources of lead in the Atlantic and oceanic areas in the Atlantic to determine the location of oceanic foraging grounds. The Pb isotope ratios in the scute of oceanic-stage green turtles indicated that turtles use different regions in the Atlantic and that they are capable of transatlantic migrations. We compare the oceanic locations identified by this study with those suggested by two previous studies.
KeywordsGreen Turtle Oceanic Area Saharan Dust Lead Isotope Ratio Straight Carapace Length
This research was funded by a Boyd Lyon Sea Turtle Fund Scholarship, the Florida Sea Turtle License Plate Grants Program, the PADI Foundation, the Explorers Club Exploration Fund, the National Fish and Wildlife Foundation, National Marine Fisheries Service, U.S. Fish and Wildlife Service, and Sigma Xi. We thank Projeto Tamar, especially the staff at Almofala and Santa Catarina in Brazil, and C. Lagueux and C. Campbell of the Wildlife Conservation Society in Nicaragua, and J. Pfaller, M. Pajuelo and H. Vander Zander in Florida for assistance with sample collection. Bahamas collections were made in collaboration with the Bahamas National Trust, S. Connett and B. Crouchley. All samples were collected under appropriate national research permits, imported under CITES permits (09US724540/9 and 10US724540/9) and collected and processed in compliance with the Institutional Animal Care and Use Committee at the University of Florida. We also thank R. Zenil-Ferguson, J. Ferguson and H. Vander Zanden for assistance with the statistical analyses and J. Curtis for his help with the carbon and nitrogen stable isotope analyses.
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