Can corals adapt to climate change and ocean acidification?

New research from American Samoa suggests that at least some coral can withstand warmer waters

For plants, animals and marine life whose environment changes, their options are stark and simple: Move, adapt or die.

But when the marine life in question is a coral reef cemented to the ocean floor and the threat is climate change, the outlook appears grimmer, said scientists presenting new findings here at the annual meeting of the American Association for the Advancement of Science.

Even small temperature rises of 1 to 2 degrees Celsius in the ocean can make corals more prone to bleaching, a kind of sudden death that occurs when corals expel the algae that normally live inside them, providing them with food and their bright coloration.

Scientists are also worried that, as carbon dioxide emissions rise, the ocean will absorb greater amounts of the greenhouse gas, shifting the chemistry of seawater. As the ocean becomes more acidic, it will be harder for corals to grow. Eventually, ocean water could become corrosive, dissolving reefs faster than corals can grow.

The question now is whether reef-building corals have the capacity to adapt to those changes.

“Can reefs disappear? That’s the question,” said Joanie Kleypas of the National Center for Atmospheric Research. “We don’t have a lot of information on this.”

One example comes from the Galapagos Islands, where a strong El Niño event in the early 1980s bleached more than 95 percent of corals. Then a species of sea urchin moved in and started chewing the reef, she said.

“Reefs that were there for hundreds or thousands of years disappeared in a matter of about a decade,” Kleypas said. “Some people think it’s a glimpse into the future … an example of what we might expect in a high-CO2 world.”

But there is some evidence to suggest all coral reefs aren’t created equal, said Stephen Palumbi, a professor of marine science at Stanford University. He’s studying what appear to be unusually resilient reefs off the coast of Ofu Island in American Samoa.

Lauren Morello and Climatewire, Scientific American, 23 February 2010. Full article.

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