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American Association for the Advancement of Science

What caused an ancient coral catastrophe?

Pocillopora coral in Panamá dying from desiccation during the 2010 La Niña event.
[Photo credit: Lauren Toth]

Millions of tiny animals create ocean coral reefs when they create shells for themselves out of a cement-like ooze. These reefs are important because they provide a home for lots of different kinds of sea life. When the reefs get "sick" and the coral stop building, it can be a sign that something major has changed in the ocean.

Four thousand years ago, coral reefs off the coast of Panama stopped growing -- and they didn't start growing again for about 2,600 years, according to Lauren Toth of the Florida Institute of Technology and her fellow scientists. In the 5 July issue of Science, the researchers describe how they discovered this huge coral catastrophe. They pushed a long aluminum pipe like a straw into the Panama coral reefs, using it to pull out long chunks of the reef that have been growing for 6000 years.

By examining the chunks carefully, the researchers were able to see when the coral stopped growing. It turns out that the corals stopped growing at the same time that a Pacific climate pattern called El Niño Southern Oscillation, or ENSO, started to change. The ENSO got stronger and happened more often during the coral catastrophe, making the ocean water warm and muddy. Corals don't grow well in water like that.

Could the same thing happen to coral reefs today? As the planet gets warmer, some scientists think that the ENSO will get stronger and happen more often -- just like it did 4,000 years ago. If that happens, there might be a second coral catastrophe. The good news is that that ancient corals eventually started growing again, Toth and the others say. So it's possible that modern coral reefs would also rebuild themselves if they were damaged.