As oceans become acidic, coral reefs on the brink of extinction

LONDON: Coral reefs around the world are facing the threat of extinction by the end of the century as the oceans are increasingly becoming acidic, a new study has warned.
New evidence from volcanic seeps — fissures in the ocean floor that leak gases and minerals — suggested a bleak future for the reefs that harbour the world’s richest marine ecosystems.
A team of scientists who carried out the research said like man-made sources of carbon dioxide, the seeps are making the water around them more acidic.
The study showed that reductions in reef diversity and complexity as pH values fell from 8.1 to 7.8, indicating greater acidity. And at values below 7.7, reef development ceased altogether.
Climate change experts estimate that by the end of the century, ocean acidity worldwide will change in a similar way because of CO2 emissions . The latest Intergovernmental Panel on Climate Change forecast says rising concentrations of CO2 will reduce ocean pH from its present level of 8.1 to 7.8.
Writing in the journal Nature , authors of the new study said that the effect of a pH drop below 7.8 would be “catastrophic” for the coral reefs. “These ‘champagne reefs’ are natural analogues of how coral reefs may look in 100 years if ocean acidification conditions continue to get worse,” said Chris Langdon , from the University of Miami in the US, who led the seep reef research.
“The seeps are the closest we can come to simulating the effect of man-made CO2 emissions on a coral reef. They allow us to see the end result of the complex interactions between species under acidic ocean conditions.”
As acidity rose closer to the seeps, the coral cover remained constant but changed drastically. It became dominated by boulder-like massive porites corals.