Fieldwork undertaken at University of Sydney’s One Tree Island Research Station and published in Nature provides evidence that ocean acidification is beginning to slow coral reef growth.
It is estimated that around 40% of CO2 emitted into the atmosphere are absorbed by the ocean, which in turn become more acidic, potentially impacting the calcification process underlying the architecture of coral reefs.
Scientists predict that reefs could switch from carbonate calcification to dissolution within the century due to this acidification process.
A team of researchers, led by Stanford University, brought the pH of a reef on One Tree Island closer to what it would have been in pre-industrial times, based on estimates of atmospheric CO2 from that era. They then measured the reef's calcification in response to this pH increase. They found calcification rates under these manipulated pre-industrial conditions were higher than today.
One Tree Island is a unique reef ecosystem that, at low tide, forms a ponded lagoon surrounded by a coral reef edge. It is an ideal habitat for researchers to monitor reef response to changes in seawater conditions enclosed within the lagoon
Previous studies have demonstrated large-scale declines in coral reefs over recent decades. However, it has been hard to pinpoint exactly how much of the decline is due to acidification and how much is caused by other anthropogenic stressors like ocean warming, pollution, and over-fishing.
Increasing the alkalinity of ocean water around coral reefs has been proposed as a geoengineering measure to save shallow marine ecosystems. The results reported here show this idea could be effective. However, the practicality of implementing such measures would be almost impossible at all but the smallest scales.