The increase in atmospheric carbon dioxide is leading to an increase in dissolved CO2 in the oceans, leading to another increase in hydrogen ions and therefore a relative acidification, although the pH still remains slightly alkaline. In addition, this will also lead to fewer available carbonate ions. This concentration contributes to the transformation of calcium ions from a solid state (calcium carbonate) to a liquid state. Thus, the calcification rate will similarly decrease in all carbonate skeletal organisms, including corals. The risk of such a drop in calcium carbonate saturation is that dissolution factors, combined with mechanical destruction and bioerosion, will reverse coral reef construction and start fragmentation of the structure. It is generally thought that the concentration of atmospheric carbon dioxide, currently of 386 ppm, should not exceed 450-500 ppm to avoid this situation. However, according to IPCC scenarios, such values will be reached in less than a century. More research is required to determine the effects of increasing seawater acidification on more coral species, specifically through physiological studies on corals and their symbiotic zooxanthellae to establish the potential adaptability of some species. This report is available in English, French and Spanish.
Salvat B. & Allemand D., 2009. Acidification and Coral Reefs. CRISP Scientific Review. pp 1-32. Report.
