Physiological Responses of Benthic Invertebrates to Ocean Acidification and Hypoxia

Climate change caused by massive emissions of carbon dioxide to the atmosphere promotes three significant changes in ocean conditions, including warming, ocean acidification, and hypoxia.  All of these environmental changes can affect the physiology of marine organisms, which in turn, can alter the survival, growth, and reproduction of individuals, with important consequences for populations and communities. We have used field experiments and laboratory assays to investigate the tolerance of selected invertebrate taxa from deep and shallow marine waters to these potential stresses. Deep-sea urchins (Allocentrotus fragilis), crabs (Chionoecetes tanneri) and brachiopopds (Laqueus sp.) exposed in laboratory experiments to ocean pH levels expected under future climate scenarios exhibited impaired capacities for acid-base balance, reduced rates of respiration, or both. In situ studies of deep-sea urchins under hypoxia and normoxic conditions indicate that the ongoing expansion and intensification of the oxygen minimum zone off central California is limiting their respiration rates, and likely to affect their metabolic performance. The physiological responses of these deep-sea invertebrates suggest that the function of deep-sea communities may be altered directly or indirectly by climate-related changes in ocean conditions.