Coral growth rate plummets in 30-year comparison

PUBLIC RELEASE DATE: 17-Sep-2014

Contact: Ken Caldeira
Carnegie Institution

Coral growth rate plummets in 30-year comparison

A team of researchers working on a Carnegie expedition in Australia's Great Barrier Reef has documented that coral growth rates have plummeted 40% since the mid-1970s. The scientists suggest that ocean acidification may be playing an important role in this perilous slowdown.

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Coral reefs are havens for biodiversity and crucial for the economies of many coastal communities. But they are very sensitive to changes in ocean chemistry resulting from human activity. Since the beginning of the Industrial Revolution about one-third of the carbon dioxide, CO2, which has been released into the atmosphere from fossil fuel combustion and land use change has been absorbed by the oceans, where it damages coral reefs.

Coral reefs use a mineral called aragonite to make their skeletons, a process called calcification. It is a naturally occurring form of calcium carbonate, CaCO3. When carbon dioxide from the atmosphere is absorbed by the ocean, it forms carbonic acid, H2CO3, which makes the ocean more acidic and decreases its pH. This makes it more difficult for many marine organisms to grow their shells and skeletons, and threatens coral around the globe.

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If the reef in Australia is as sensitive to ocean acidification as was estimated by lead author Jack Silverman of Israel Oceanographic & Limnological Research Ltd in his previous work in Israel, then the increase in ocean acidification would be sufficient to explain the 40 percent decline.

Previous work by the group projected that all of the reefs in the world may be dissolving in a few decades if current carbon dioxide emission trends continue.

"Coral reefs are getting hammered," said Caldeira. "Ocean acidification, global warming, coastal pollution, and overfishing are all damaging coral reefs. Coral reefs have been around for millions of years, but are likely to become a thing of the past unless we start running our economy as if the sea and sky matters to us very soon."

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