Biotic and abiotic factors affect the nest environment of embryonic leatherback turtles, Dermochelys coriacea

Abstract

Clutches of leatherback turtles, Dermochelys coriacea, have lower hatching success than those of other sea turtles, but causes of high embryonic mortality are unknown. We measured characteristics of clutches along with spatial and temporal changes in PO2 and temperature during incubation to determine the extent to which they affected the developmental environment of leatherback embryos. Minimum PO2 in nests decreased as both the total number and mass of metabolizing embryos increased. Increases in both the number and mass of metabolizing embryos caused an increase in maximum nest temperature. However, neither PO2 nor temperature was correlated with hatching success. Our measurements of relatively high nest PO2 (lowest 17.1 kPa or 16.9% O2) indicate that hypoxia apparently does not cause the low hatching success of leatherback clutches. Oxygen partial pressure increased and temperature decreased from the center toward the periphery of leatherback nests. We inferred from these measurements that positions of eggs within nests vary in quality and potentially affect overall developmental success of entire clutches. The large metabolic mass of leatherback clutches and limits to gas flux imposed by the sand create a situation in which leatherback embryos collectively affect their own environment.