Abstract

Bahía Salado is the southernmost foraging site known for the black turtle (Chelonia mydas) and also hosts an important seagrass ecosystem composed of Zostera chilensis, which is only known to occur at one other site along the 4300 km of Chilean coastline. Both of these marine species are classified as Endangered by the IUCN. Although in other parts of the world there is much scientific evidence for the dietary dependence on seagrass pastures by C. mydas, almost no information exists on their trophic relationships in the eastern and southeastern Pacific Ocean. Here we present preliminary data on the dietary components of C. mydas aggregated in the southernmost foraging habitat known for the Eastern Pacific population. Stable isotope analysis (SIA) is a minimally invasive technique that allows for the establishment of trophic relationships (prey-predator), distribution ranges, ontogenetic changes in diet and migratory movements. We investigated the composition of principal diet components by analyzing stable nitrogen and carbon (δ 15 N and δ 13 C respectively) proportions in blood, skin and carapace samples obtained from seven black turtles aggregated in Bahía Salado. Putative food items were also analyzed, including Z. chilensis, Ulva sp, Macrocystis pyrifera, Asparagopsis armata, Ceramium sp, Chondrus acanaliculatus and Anthothoe chilensis. Residency and recruitment was also assessed using individual’s stable isotope signatures compared to signatures of primary producers. Our results provide the first data on the ecological features of C. mydas and the southernmost known feeding ground in its regional distribution. The characterization of this unique habitat will help to understand black turtle ecology in the Southeast Pacific and highlights the plasticity this species has developed to flourish in regions outside the Pacific’s’ tropical and subtropical boundaries.