COSTS AND CONSEQUENCES OF LIFE IN A HIGH CO2 OCEAN

Ocean acidification (OA) is predicted to have large impacts on marine ecosystems ranging from polar seas to tropical reefs. These impacts are not well understood at the community and ecosystem level, although they are expected to be substantial, resulting in range shifts and population declines. Currently we lack a comprehensive understanding of the resilience of marine organisms to conditions of CO₂-acidified seawater and research is needed that investigates the effects of elevated CO₂ on a variety of physiological processes, in addition to calcification. The research community is taking a number of approaches to understanding the physiological “weak links” underlying thresholds in CO₂ tolerance in both adult and juvenile life stages and asking whether animals have the potential to “flex” their physiology to compensate for the impacts of CO₂-driven acidification. While it is becoming clear that responses to elevated CO₂ will vary amongst organisms, changes in metabolism and growth is a common thread in much of the research to date, suggesting that there are changes in energy budget associated with an animal’s response to OA conditions. As animals change their allocation of resources towards one biological process, such as calcification, we are beginning to see the costs associated with these adjustments in other biological processes, such as decreases in stress tolerance. Furthermore, it is becoming increasingly clear that research efforts should consider the multiple stressors that are predicted to change in global climate change scenarios to make accurate predictions of organismal resilience. The ability and manner in which an organism responds to increased CO₂ levels is influenced by its exposure to other changes in environmental conditions such as increased temperature. Data from studies on marine invertebrates will be used to highlight some of these important physiological considerations.