REICH, K.J.*; BJORNDAL, K.A.; BOLTEN, A.B.; University of Florida; University of Florida; University of Florida: Tracking Ontogenetic Shifts in Diet and Habitat of Juvenile Sea Turtles with Stable Isotopes

With the exception of loggerheads (Caretta caretta), little is known about the habitat use and diet of juvenile sea turtles. Stable ¹³C and ¹⁵N isotope analyses of scutes–the top, keratin layer of a turtle shell–were used to investigate diet and trophic position of North Atlantic juvenile sea turtles (Chelonia mydas, Eretmochelys imbricata, Lepidochelys kempii) prior to their recruitment to neritic waters in Florida and the Bahamas. Scute samples were collected from green turtles (C. mydas), hawksbills (E. imbricata), and Kemp�s ridleys (L. kempii) that stranded on Florida beaches and from our study population of green turtles in the Bahamas between 2001 and 2005. We confirmed that scute carries a record of previous diet and habitat use by comparing samples of old and new scute from green turtles that had recently recruited to seagrass meadows in the Bahamas. To establish a baseline isotope signature for sea turtles feeding in the pelagic zone in deep water, oceanic habitat, we analyzed samples from juvenile loggerheads residing in the waters over the mid-Atlantic Ridge for ¹³C and ¹⁵N. Results indicate that, during the first years of life, juvenile loggerheads, green turtles, hawksbills, and Kemp�s ridleys all occupy the same type of habitat and feed at a similar trophic level. Our analyses of ¹³C and ¹⁵N signatures of green turtles provide evidence of a shift from a primarily carnivorous diet and pelagic zone, oceanic habitat to an herbivorous diet and neritic habitat. We have established that scute retains a history of stable isotope signatures and that stable isotope analysis is a powerful tool in the ongoing investigation of the ontogenetic shift in diet and habitat of juvenile sea turtles.