Ocean acidification’s effect on coral confirmed

Scientists have managed to prove ocean acidification is slowing the growth of coral reefs around the world.

Greenhouse gases, such as carbon dioxide, not only affect nature above land but also below it. Ocean acidification results from carbon dioxide reacting with seawater, forming carbonic acid and also reducing the amount of carbonate ions shellfish, coral reefs and other marine life depend on to live.

Rebecca Albright, from the Carnegie institution for Science in Washington DC, said: “Our work provides the first strong evidence from experiments on a natural ecosystem that ocean acidification is already slowing coral reef growth.

"Ocean acidification is already taking its toll on coral reef communities. This is no longer a fear for the future; it is the reality of today,” she added.

Coral is vulnerable to ocean acidification as reefs form by accumulation of calcium carbonate, known as calcification, however this becomes more and more difficult as the acidity of the surrounding water increases, lowering its pH.

In order to test this, Albright’s team manipulated the alkalinity of seawater over a reef in the southern Great Barrier Reef in Australia. The reef’s pH was increased to pre-industrial alkaline levels based on carbon dioxide atmospheric estimates.  Calcification rates were then measured and found to be higher than those currently.

Increasing the alkalinity of ocean water around coral reefs has been proposed to boost shallow water ecosystems, but the practicality of implementing this successfully has been questioned.

Ken Caldeira, involved in the study and also from the Carnegie Institution, said: “The only real, lasting way to protect coral reefs is to make deep cuts in our carbon dioxide emissions. If we don't take action on this issue very rapidly, coral reefs —and everything that depends on them, including both wildlife and local communities — will not survive into the next century."

The research is published in Nature.