Ocean acidification is not only slowly killing existing coral reefs, it is also preventing new corals from establishing themselves.
According to a study to be published in a forthcoming issue of the Proceedings of the National Academy of Sciences, Rebecca Albright and co-authors postulate from their study that recruitment levels of coral worldwide could drop by as much as 73% as a result of ocean acidification.
Basing their studies on the Elkhorn coral (Acropora palmata), a species found in the Caribbean, the authors carried out a series of experiments in which they examined whether ocean acidification threatens successful sexual recruitment of reef-building corals.
They did this by testing fertilisation, settlement, and post-settlement growth of Elkhorn coral at dissolved carbon dioxide levels that represent average ambient conditions during coral spawning and the range of carbon dioxide level increases expected to occur in this century.
The authors found average fertilisation success to decrease by 12–13%, settlement to decrease by 45–69%, and postsettlement growth to decrease by 39–50% under elevated carbon dioxide regimes. The compounding effect of ocean acidification on these early life history stages translates into a 52–73% reduction in the number of larval settlers on the reef, according to the authors.
The results of the study demonstrate that ocean acidification has the potential to impact multiple life history stages of corals. The compounding nature of these impacts suggests that ocean acidification may impact corals more severely than originally perceived.
For more information, see the paper: Albright, R, B Mason, M Miller and C Langdon (2010) Ocean acidification compromises recruitment success of the threatened Caribbean coral Acropora palmate. Proceedings of the National Academy of Sciences of the United States of America, doi: 10.1073/pnas.1007273107