Meeting Abstract
Two of the many consequences of climate change are the warming and subsequent deoxygenation of Earth’s oceans. This poses a major ecophysiological threat to marine ectotherms, where increasing temperature is traditionally considered to limit aerobic scope (ability to elevate respiration above a basal level) unidirectionally by raising metabolic rates beyond the capacity of the animal to take up adequate oxygen from its environment. In response, range-shifts within affected species to cooler, more oxygenated waters at greater depths or higher latitudes is often considered a resultant physiological strategy. However, the influence of temperature on aerobic scope in marine invertebrates is not well known. Using standard respirometry protocols applied to intertidal invertebrates from the Pacific, Atlantic, and Gulf of Mexico basins, we examined oxygen- and capacity-limited thermal tolerance in multiple taxa across two separate phyla both with (Annelida; triploblastic) and without (Cnidaria; diploblastic) circulatory systems. We find that absolute oxygen tolerance (measured as the onset of anaerobiosis, or critical partial pressure) decreases at temperatures both above and below distinct taxon-specific optima. These data suggest the loss of ventilatory capacity at temperatures colder than a species-specific optimum may inhibit ectotherms’ ability to withstand environmental hypoxia. This in turn impacts strategies such as migration, which will be both more limited and subject to acclimatization capacity than previously considered.
