Facing a Physiological Crossroad: Response of an Intertidal Sculpin to a Multi-stressor Challenge

As we move into the Anthropocene, organisms inhabiting marine environments will continue to face growing challenges associated with changes in ocean pH (ocean acidification), dissolved oxygen (dead zones) and temperature. These factors, in combination with naturally variable environments such as the rocky intertidal, may create extreme physiological challenges for organisms that are already performing near their biological limits. Although numerous studies have examined the impacts of climate related stressors on intertidal animals, little is known about the underlying physiological mechanisms driving adaptation to ocean acidification and how this may alter organism interactions, particularly in marine vertebrates. Therefore, we have investigated the effects of decreased ocean pH on the hypoxia response of an intertidal sculpin, Clinocottus analis. We used both whole animal and biochemical based analyses to examine how the energetic demands associated with acclimation to low pH environments may impact the fish’s reliance on facultative air breathing in low oxygen environments. Our study demonstrated that acclimation to OA results in elevated routine metabolic rates (RMR) and acid base regulatory capacity (Na+/K+ ATPase activity). These in turn had down stream effects that resulted in decreased hypoxia tolerance (i.e. elevated Pcrit). Furthermore, we present evidence that these fish may be living near their physiological capacity when challenged by ocean acidification. This serves as a reminder that the susceptibility of teleost fish to changes in ocean pH may be underestimated, particularly when considering the multiple stressors that many experience in their natural environments.