Some coral reefs in naturally warm waters near Australia appear to be relatively unaffected by the kind of climate-change-induced "coral bleaching" that has damaged reefs in regions where water temperatures have risen more dramatically, scientists have found.

The findings, published in the online journal Geophysical Research Letters, appear to support a theory that a natural "ocean thermostat" prevents surface water temperatures from climbing above 88 degrees Fahrenheit in open oceans, the researchers said.

Scientists from the National Center for Atmospheric Research in Colorado and the Australian Institute of Marine Science studied the correlation between sea temperatures and bleaching — a whitening caused by a loss of algae — by analysing sea-surface temperatures from 1950 to 2006 in tropical waters. They documented relatively few episodes of coral bleaching in the Western Pacific Warm Pool, an area northeast of Australia where the temperature of the naturally warm waters has risen little in recent decades.

They concluded that reefs that have evolved in naturally warm waters may enjoy a degree of protection from global warming by the "ocean thermostat," while reefs in cooler waters do not.

"Global warming is damaging many corals, but it appears to be bypassing certain reefs that support some of the greatest diversity of life on the planet," said lead researcher Joan Kleypas. "In essence, reefs that are already in hot water may be more protected from warming than reefs that are not. This is some rare hopeful news for these important ecosystems."

The Washington Post