Ocean acidification already taking toll on coral reef growth

Washington D.C.: Seems like world's coral reefs are running out of time as a new study has revealed that ocean acidification is causing the longest global coral die-off and preventing them from growing fast enough to bounce back.

The international team of scientists from the Carnegie Institution for Science, Rice University and other institutions has performed the first experiment to manipulate seawater chemistry in a natural coral-reef community to determine the effect that excess carbon dioxide released by human activity is having on coral reefs.

The research was conducted in a lagoon on the southern Great Barrier Reef in Australia in 2014. By controlling the alkalinity on a portion of the reef, the team was able to examine how fast the reef is growing today and compare that with growth rates in less acidic conditions that existed prior to the Industrial Revolution.

Lead author Rebecca Albright said that the work provides the first strong evidence from experiments on a natural ecosystem that ocean acidification is already causing reefs to grow more slowly than they did 100 years ago. 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.

Researcher Kai Zhu designed a statistical model that was capable of quantifying the variation that occurred both naturally, in a portion of the reef that was measured as an experimental control, and as a result of the experiment. The data showed that the reef grew about 7 percent faster when seawater acidity approximated that of preindustrial conditions.

Ken Caldeira, the study's lead scientist, said that the only real, lasting way to protect coral reefs is to make deep cuts in our carbon dioxide emissions, adding "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 study is published in this week's issue of Nature.