Abstract
The effects of climate change and associated increases in temperature on organisms are a major focus of scientific research, but how these impacts play out within ecological contexts is complex and hence often ignored. For example, the influence of predation risk (nonconsumptive effects, NCEs) can alter behavior, creating scenarios where individual physiological responses depend on the interaction between abiotic conditions, such as temperature, and the presence of risk in the environment. Yet a mechanistic understanding of how the interplay among abiotic and biotic stressors, especially NCEs, shapes the short-term physiological performance of intertidal organisms remains limited. From both physiological and biochemical perspectives, we explored the short-term interaction between temperature, feeding history, and predation risk from a predatory snail (Nucella laplats) on the intertidal mussel (Mytilus edulis). We measured heart rate, key aerobic (citrate synthase) and anaerobic (cytosolic malate dehydrogenase) metabolic enzymes, and total antioxidant capacity to elucidate metabolic strategies utilized by mussels in short-term, multi-stressor events. After 60 min of continuous exposure to increased temperature and predation risk, heart rate and aerobic capacity were primarily impacted by temperature, whereas total cytosolic malate dehydrogenase activity displayed an antagonistic relationship in response to the combined effects of feeding history and predation risk. In contrast, total antioxidant capacity displayed a three-way interaction among all treatments (feeding history, temperature and predation risk), driven by opposing thermal responses between fed and starved mussels in the absence of risk. Our results suggest that although mussels are fairly tolerant of acute stress events, the interaction of feeding history and predation risk may prevent them from launching a coordinated stress response when thermal stress is high.