Rising ocean acid levels ‘among top threats to coral’

Oceans’ rising acid levels have emerged as one of the biggest threats to coral reefs, acting as the “osteoporosis of the sea” and threatening everything from food security to tourism and livelihoods, the head of a US scientific agency said.

The speed by which the oceans’ acid levels have risen caught scientists off guard, with the problem now considered to be climate change’s “equally evil twin”, said National Oceanic and Atmospheric Administration chief Jane Lubchenco.

“We’ve got sort of the perfect storm of stressors from multiple places really hammering reefs around the world,” said Ms Lubchenco, who was in Australia to speak at the International Coral Reef Symposium in the north-east city of Cairns, near the Great Barrier Reef. “It’s a very serious situation.”

Oceans absorb excess carbon dioxide in the atmosphere, leading to an increase in acidity. Scientists are worried about how that increase will affect sea life, particularly reefs, as higher acid levels make it difficult for coral skeletons to form.

Ms Lubchenco likened ocean acidification to osteoporosis — a bone-thinning disease — because researchers are concerned it will lead to the deterioration of reefs.

Scientists initially assumed that the carbon dioxide absorbed by the water would be sufficiently diluted as the oceans mixed shallow and deeper waters. But most of the carbon dioxide and the subsequent chemical changes are being concentrated in surface waters, Ms Lubchenco said.

“And those surface waters are changing much more rapidly than initial calculations have suggested,” she said. “It’s yet another reason to be very seriously concerned about the amount of carbon dioxide that is in the atmosphere now and the additional amount we continue to put out.”

Higher acidity levels are especially problematic for creatures such as oysters because they slow the growth of their shells.