Blood Oxygen Depletion in Diving California Sea Lions: How Close to the Limit

Abstract

Abstract : The management and depletion of O2 stores underlie the dive capacities of marine mammals and are fundamental to the concept of an aerobic dive limit (ADL, dive duration associated with the onset of post-dive blood accumulation). The ADL, which is often calculated (cADL) on the basis of total body O2 stores and an estimated diving metabolic rate, has become an essential concept in the interpretation of diving behavior and foraging ecology (Kooyman and Ponganis 1998); however, the actual rate and magnitude of O2 store depletion during dives has not been determined in any otariid. This project will document the rate and magnitude of blood O2 store depletion during diving in California sea lions, and use this information to develop an experimental approach to assess the aerobic dive limit (ADL) and O2 store depletion in this and other otariid species. The specific objectives of this project are: 1) Document venous and arterial PO2 profiles in lactating California sea lions (Zalophus californianus) while diving during foraging trips to sea, 2) Characterize the O2-hemoglobin (Hb) dissociation curve of sea lion Hb, 3) Use the dissociation curve to convert the PO2 profiles into % Hb saturation profiles that will then be used to calculate rate and magnitude of blood oxygen depletion, and 4) Refine vascular access techniques which could be used for future investigations (i.e., blood N2 absorption during dives; blood gas (pH, PCO2, PO2) and blood lactate responses during dives; blood indices for stress responses to captivity, training, and/or sound exposure; application of such techniques to other species including dolphins).