WALLACE, B.P. *; SEMINOFF, J.A.; KILHAM, S.S.; SPOTILA, J.R.; DUTTON, P.H.; Duke University Marine Lab; NOAA-National Marine Fisheries Service, Southwest Science Fisheries Center; Drexel University; Drexel University ; NOAA-National Marine Fisheries Service, Southwest Science Fisheries Center: Leatherback turtles as oceanographic indicators: stable isotope analyses reveal a trophic dichotomy between ocean basins

Oceanographic sampling is often limited to local “snapshots” of complex, transient and widespread phenomena. Migratory pelagic animals can provide important integrated information about broad-scale oceanographic factors to improve understanding of complex ocean processes and their effects on marine biodiversity. Leatherback turtles (Dermochelys coriacea) are long-lived, migratory reptiles and are specialist predators for gelatinous prey. In addition, differences in morphometrics, reproductive output, and population trends exist between inter-basin leatherback populations, and could be due to differential resource availability on foraging grounds. Therefore, we analyzed stable carbon and nitrogen stable isotopes ratios δ¹³C and δ¹⁵N) of tissues from nesting leatherback populations from the eastern Pacific and North Atlantic Oceans to establish differences between oceanographic processes in both basins. While δ¹³C signatures were similar between eastern Pacific and North Atlantic leatherbacks, reflecting the pelagic foraging strategy of the species, eastern Pacific leatherback δ¹⁵N signatures were significantly enriched relative to North Atlantic leatherback δ¹⁵N signatures. This δ¹⁵N discrepancy reflects inter-basin differences in nitrogen cycling regimes and their influence on primary productivity being transferred through several trophic levels. These results demonstrate intriguing potential for combining high-order marine consumer movements, habitat preferences, and stable isotope signatures with ocean sampling to elucidate interactions between oceanographic processes and marine biodiversity.