Climate change causes ocean warming and acidification on global scales. In contrast to well established effects of warming, evidence for the effects of rising carbon dioxide (CO2) on marine ecosystems is only just emerging. However, future scenarios indicate threats to marine life through combinations of rising CO2, warming and more frequent hypoxia events. For realistic future climate effect scenarios, key physiological mechanisms and their responses to combined stressors require identification. These are physiological mechanisms which define species performance, including their capacity to interact, e.g. in food webs (1). Many ecosystem changes likely occur when temperature drifts beyond species-specific limits and causes a shift in phenology or fitness. High sensitivity to elevated CO2 levels may involve a low capacity for acid–base regulation, as seen in lower marine invertebrates (2). The disturbed extracellular acid–base status affects processes involved in growth, calcification, neural functions, blood gas transport and behavioural capacities (2). Current evidence indicates elevated sensitivity to elevated CO2 levels towards the extremes of thermal windows (3). The ultimate consequence may be a narrowing of thermal tolerance windows and associated ranges of geographical distribution and of the performance at ecosystem level. Thus, CO2 may exacerbate warming effects on marine ecosystems. Future research will have to test these concepts under realistic climate and ocean acidification scenarios and in various marine ecosystems between the tropics and the poles.
Pörtner, H. O., 2009. Ecosystem impacts of climate change and ocean acidification: A case for “global” conservation physiology. Comparative Biochemistry and Physiology – Part A: Molecular & Integrative Physiology 153:2, 59. Abstracts of the Annual Main Meeting of the Society of Experimental Biology, 28th June – 1st July, Glasgow, UK .Abstract.