Isotopic niche overlap among foraging marine turtle species in the Gulf of Mexico

• Published in: Ecology and evolution Vol. 13; no. 11; pp. e10741 - n/a
• Main Authors: Weber, Savannah, Cullen, Joshua A., Fuentes, Mariana M. P. B.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01-11-2023; John Wiley and Sons Inc; Wiley
• Subjects: Aquatic reptiles; Carbon; Community Ecology; Ecological niches; Environmental protection; Epidermis; Foraging behavior; foraging ecology; Habitat utilization; Habitats; Isotopic tracers; Laboratories; Marine ecology; marine turtles; Niche overlap; Niches; Nitrogen; Population Ecology; Reptiles & amphibians; Spatial Ecology; Species; stable isotope; Stable isotopes; Sulfur; sulfur isotope; Sulfur isotopes; Sympatric populations; sympatric species; Trophic Interactions; Turtles; Wildlife conservation; Crystal River; Gulf of Mexico; Florida; United States > US; sympatric species; foraging ecology; stable isotope; sulfur isotope; niche overlap; marine turtles
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.10741

Sympatric species may overlap in their use of habitat and dietary resources, which can increase competition. Comparing the ecological niches and quantifying the degree of niche overlap among these species can provide insights into the extent of resource overlap. This information can be used to guide multispecies management approaches tailored to protect priority habitats that offer the most resources for multiple species. Stable isotope analysis is a valuable tool used to investigate spatial and trophic niches, though few studies have employed this method for comparisons among sympatric marine turtle species. For this study, stable carbon, nitrogen, and sulfur isotope values from epidermis tissue were used to quantify isotopic overlap and compare isotopic niche size in loggerhead (Caretta caretta), green (Chelonia mydas), and Kemp's ridley (Lepidochelys kempii) turtles sampled from a shared foraging area located offshore of Crystal River, Florida, USA. Overall, the results revealed high degrees of isotopic overlap (>68%) among species, particularly between loggerhead and Kemp's ridley turtles (85 to 91%), which indicates there may be interspecific competition for resources. Samples from green turtles had the widest range of isotopic values, indicating they exhibit higher variability in diet and habitat type. Samples from loggerhead turtles had the most enriched mean δ34S, suggesting they may forage in slightly different micro‐environments compared with the other species. Finally, samples from Kemp's ridley turtles exhibited the smallest niche size, which is indicative of a narrower use of resources. This is one of the first studies to investigate resource use in a multispecies foraging aggregation of marine turtles using three isotopic tracers. These findings provide a foundation for future research into the foraging ecology of sympatric marine turtle species and can be used to inform effective multispecies management efforts.
Understanding how sympatric species compare in resource use can provide insight into their ecological role and aspects of their foraging ecology. To investigate this, we collected skin samples for carbon, nitrogen, and sulfur stable isotope analysis from loggerhead, green, and Kemp's ridley turtles sampled in a shared coastal foraging area located in the northeastern Gulf of Mexico. Our results revealed high degrees of isotopic overlap among all three species, which indicates little resource partitioning and further suggests that there may be interspecific competition for resources.