Meeting Abstract
Environmental oxygen availability, relative to requirements, is an important determinant of habitat suitability for marine organisms and provides a measure of effective metabolic scope for all life functions beyond basic maintenance. As the balance between metabolic oxygen demand and environmental supply changes with climate, energetic trade-offs occur to facilitate survival, or alternative habitat is sought to alleviate metabolic constraints. As the global incidence of low oxygen waters, known as hypoxic zones, increases each year, it has become crucial to understand how marine organisms respond to hypoxia. Coastal shark species of varying lifestyle such as blacktip sharks (Carcharhinus limbatus), and spiny dogfish sharks (Squalus acanthias)) may be vulnerable to hypoxia due to oxygen-intensive behaviors, such as high-speed swimming, migration, etc. Hypoxia, in conjunction with temperature-induced increases in oxygen demand, may limit performance and viable habitat of coastal shark species. In order to accurately forecast shark niches, and habitat selection in the face of these climate shifts, we must first determine species-specific tolerances to hypoxia. Hypoxia tolerance was measured using Pcrit, defined as the critical oxygen partial pressure at which oxygen demand equals supply. Using respirometry, we determined Pcrit for C. limbatus and S. acanthias, and examined how Pcrit varies with ventilation method and temperature. Furthermore, we quantified behavioral responses to hypoxia and the blood stress response associated with acute exposure to critical oxygen levels. Results from this study provide a physiological basis for predicting viable metabolic habitat for these species, and insight into the physiological consequences of hypoxia-induced stress.
