Repeating an experiment 47 years after it was originally carried out has revealed some rare good news about coral reefs 鈥� some species appear to have become significantly better at surviving temperature increases.
In 1970, marine zoologist collected three species of coral from a reef in K膩ne鈥榦he Bay, Hawaii. When he put them in a chamber and gradually heated the water, he found that they simply couldn鈥檛 tolerate increases of 1 to 2 degrees. They started to bleach, ejecting the colourful algae that normally live within them. Without these, coral die.
But Coles got a different result when he repeated the experiment last year using corals from the same area, raising them to the same temperatures that killed most of the corals in the earlier experiment. This time, it took a few days longer for the corals to begin bleaching, and more than half of them survived.
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鈥淭hat was a big surprise, that we could get a 2-degree adjustment in less than 50 years,鈥� Coles says.
Glimmer of hope
The finding is in line with anecdotal that on some reefs around the world, more corals seem to be surviving after bleaching events. While Coles hasn鈥檛 explored the biological mechanisms at play, other suggests that some corals can adapt to higher temperatures by associating with species of algae that are more tolerant of heat stress.
It鈥檚 not clear yet whether corals in Hawaii are individually acclimatising to rising temperatures, or whether they have evolved genetic mechanisms for thermal tolerance that they will pass onto future generations, says , of the University of Texas at Austin. Either way, it鈥檚 good news, he says, but genetic adaptation may have more lasting benefits.
Coles doesn鈥檛 think the change in corals will be enough to completely counteract the effects of global warming. But the finding might suggest that, if we take action on climate change now, some coral reefs may still exist in a hundred years鈥� time, he says.
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