Some corals seem to be resilient to ocean acidification.

As carbon dioxide emissions rise, ocean waters are absorbing more of the gas and becoming less alkaline, threatening the ability of corals and other marine organisms to make skeletons and shells. Lucy Georgiou at the University of Western Australia in Perth and her colleagues exposed colonies of Porites cylindrica coral on Australia's Great Barrier Reef to flumes of modified sea water. This lowered the ambient pH around the animals so that it was similar to conditions that are predicted for oceans at the end of the century. After six months, the researchers found no difference in the growth rate of the corals' skeletons between controls and those living in lower pH conditions.

The corals naturally produce a fluid that bathes the growing parts of their skeletons, and the team found that the fluid had a higher pH than the reef waters for all the corals in the experiment. This suggests that some corals can regulate their internal pH to tolerate a certain level of ocean acidification, the authors say.

Proc. Natl Acad. Sci. USA (2015)