A comparison of stable isotope values in epidermis and blood of nesting leatherback sea turtles in the Northwest Atlantic Ocean

Leatherback sea turtles ( Dermochelys coriacea ) are highly migratory, which poses significant challenges for conservation efforts. This study explored the application of stable isotopes to better understand habitat use and behaviors of Florida’s nesting leatherbacks. Our main objectives were to (1) determine if the structure of isotope data were consistent with known pre-nesting foraging individuals, (2) monitor changes in δ ¹³C and δ ¹⁵N isotope values across epidermis and whole blood during the nesting period, and (3) compare isotopic values between tissue types. Distinct isotopic clusters were identified in δ ¹³C values, suggesting variation among individuals that may reflect differences in pre-nesting foraging ecology. Whole blood isotope values remained relatively unchanged across the nesting season for sampled individuals, whereas epidermis fluctuated, contrary to expectations of isotopic turnover rates for these tissues. The isotopic composition of epidermis and whole blood was significantly correlated, allowing for tissue-specific conversion equations. We suggest that studies on leatherbacks should consider the variability in different tissues, as we found blood samples had the least variation in isotopic composition across the nesting season. Together, these results provide new insight into leatherback foraging ecology and support the use of stable isotopes as a growing complementary tool for conservation monitoring.