Carbon dioxide has been emitted into the atmosphere at ever increasing levels since the Industrial Revolution. The ocean absorbs about one-quarter of the carbon dioxide added to the atmosphere by human activities. The absorption of carbon dioxide by the ocean triggers a series of chemical reactions which produces carbonic acid (see figure below), making the oceans more acidic (lower pH) and a decreasing the concentration of carbonate in the water.
Acidification was flagged by The Royal Society in 2005 as requiring further research. Their paper was the spur for the first stage of the research project now known as Future Reef.
Carbonate is vital to the building of coral reefs. Without carbonate, corals are not able to build the skeletal structure that provides the foundation for coral reefs and ultimately the reef structure erodes away. In addition, even small changes in water chemistry associated with ocean acidification can result in coral bleaching.
If current trends in carbon dioxide emissions continue, the ocean will continue to acidify, to an extent and at rates that have not occurred for tens of millions of years. This will lead to major changes in the marine environment and compromise the long-term viability of coral reef ecosystems and the associated benefits they provide.