Located 100 km west of Key West, Florida, Dry Tortugas National Park (DRTO) is a largely untouched subtropical marine ecosystem that serves as an important developmental habitat, nesting ground, and foraging area for several species of sea turtles, including green turtles. The Park supports a recovering population of green turtles comprised of resident juveniles, subadults, and adults of both sexes; nesting females include residents and migrating females that only return to nest. Stable isotope analysis has been applied globally to describe the trophic ecology of green turtles, from urbanized bays with significant anthropogenic input, to relatively pristine ecosystems with healthy populations at carrying capacity. However, there is a paucity of published literature about the trophic ecology of green turtles in DRTO.
This study describes the trophic ecology and the isotopic niche occupied by juveniles (n = 107), subadults (n = 21), and adults (n = 89) green turtles. Using bulk flipper tissue collected from the rear flipper of green turtles found within the park, results indicate that values for δ15N (3.41‰ to 9.69‰) and δ13C (-22.43‰ to -5.38‰) fall within literature values for green turtles indicating that although all are herbivores, they fed at different trophic levels. In addition, we used Bayesian modeling (SIAR) to estimate the dietary influence of basal resources in the area on different green turtle size classes. Understanding the trophic ecology of this resident population of green turtles is instrumental for effective management that includes habitat preservation strategies.