Diet selection of sympatric marine turtles reveals the importance of diverse benthic habitats

Understanding dietary differences among sympatric marine turtles provides insights into their ecological roles and mechanisms supporting coexistence in shared foraging habitats. Stable isotope analysis (SIA) is widely used to assess marine turtle foraging ecology, yet many studies rely solely on consumer tissues, limiting inference about diet composition and selection. Here, we use SIA of epidermis from green turtles ( Chelonia mydas ), Kemp’s ridley ( Lepidochelys kempii ), and loggerhead ( Caretta caretta ) turtles alongside SIA of potential prey items in a coastal foraging ground in Florida’s Big Bend region (28.8° N, 82.78 °W). Turtles were sampled between 2016 and 2024. Using Bayesian mixing models, habitat surveys, and Chesson’s selectivity index, we assessed prey use relative to availability (i.e. selection). Green turtles exhibited predominantly herbivorous diets but selectively foraged on macroalgae and sessile prey. Kemp’s ridleys displayed a mixed diet, selecting for sessile prey. Loggerheads also selected for sessile prey, with adults incorporating smaller proportions of mobile prey than subadults. These findings reveal distinct proportional use of prey items, yet overlap in prey selection, highlighting how diverse benthic habitats support species coexistence. Identifying key resources that sustain multispecies turtle assemblages provides critical information for coastal habitat conservation and management.