Ecological complexity buffers the impacts of future climate on marine consumers

Ecological complexity represents a network of interacting components that either propagate or counter the effects of environmental change on individuals and communities 1 – 3 . Yet, our understanding of the ecological imprint of ocean acidification (elevated CO 2 ) and climate change (elevated temperature) is largely based on reports of negative effects on single species in simplified laboratory systems 4 , 5 . By combining a large mesocosm experiment with a global meta-analysis, we reveal the capacity of consumers (fish and crustaceans) to resist the impacts of elevated CO 2 . While individual behaviours were impaired by elevated CO 2 , consumers could restore their performances in more complex environments that allowed for compensatory processes. Consequently, consumers maintained key traits such as foraging, habitat selection and predator avoidance despite elevated CO 2 and sustained their populations. Our observed increase in risk-taking under elevated temperature, however, predicts greater vulnerability of consumers to predation. Yet, CO 2 as a resource boosted the biomass of consumers through species interactions and may stabilize communities by countering the negative effects of elevated temperature. We conclude that compensatory dynamics inherent in the complexity of nature can buffer the impacts of future climate on species and their communities. The complexity of ecosystems could influence how warmer waters and acidification affect marine biota. In this study, whilst individual behaviours were affected by increased CO 2 , community dynamics buffered the impacts on fish and crustaceans.