Current understanding and challenges for oceans in a higher-CO2 world

Ocean acidification is a global phenomenon, but it is overlaid by pronounced regional variability modulated by local physics, chemistry and biology. Recognition of its multifaceted nature and the interplay of acidification with other ocean drivers has led to international and regional initiatives to establish observation networks and develop unifying principles for biological responses. There is growing awareness of the threat presented by ocean acidification to ecosystem services and the socio-economic consequences are becoming increasingly apparent and quantifiable. In this higher-CO 2 world, future challenges involve better design and rigorous testing of adaptation, mitigation and intervention options to offset the effects of ocean acidification at scales ranging from local to regional. Ocean acidification, a result of increased levels of CO 2 , impacts the marine environment and its biology. This Perspective presents the current understanding of the issue and highlights future directions for research.