Using Stable Isotopes to Identify and Compare Green Sea Turtle Foraging Areas in Florida

Nearshore marine ecosystems are susceptible to stochastic environmental conditions and anthropogenic stressors that may lead to variable resource availability, resource quality,  and altered trophic structure. Evaluating productivity and identifying regions of concern is crucial for effective management and conservation.  The green sea turtle (Chelonia mydas) is a long-lived, highly migratory species that exhibits nest site and post-nesting foraging site fidelity. Reproductively active females from the same nesting beach use disparate foraging habitats. Additionally, energy required for reproduction is acquired exclusively at foraging areas. These factors make green turtle fecundity a valuable proxy to assess resource limitations and impacts at distant feeding locations that affect a broad range of taxa. In this study, we collected skin samples from nine satellite-tracked individuals and 100 untracked nesting females over two years. We combined the use of satellite tracking and stable isotope analyses of δ13C and δ15N to delineate distinct foraging aggregations of green turtles nesting on the Archie Carr National Wildlife Refuge, Florida. In order to test our hypothesis that environmental conditions at foraging grounds affect fecundity, we tested for differences in clutch size and egg mass among turtles from different foraging grounds and among years.