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Rock on: Unlocking the mystery of coral bleaching

Marc Lefkowitz  |  05/29/18 @ 11:00am  |  Posted in Climate, Plants & animals

Stephen Palumbi considers himself an optimist, despite the scary data on ocean health that keeps washing up on his shore.

<br />Stanford University Marine Biology professor Stephen Palumbi during the National Academy of Engineers meeting in Cleveland. The slide reads, Using heat-resistant corals to build future reefs ready for climate change.

A professor in Marine Sciences and Senior Fellow at the Woods Institute for the Environment at Stanford University, Palumbi researches the effects of climate change on ocean ecosystems. This year, he co-authored a report— it made an important link between rising ocean temperatures and the health of coral, a rock-like species that made headlines for its sudden and catastrophic “bleaching.” The extent of coral bleaching is widespread; affected areas, like the Great Barrier Reef in Australia, can be seen from outer space, he said during a presentation to the National Academy of Engineers hosted by Case Western Reserve University in Cleveland.

“This is a research question," he began, "even when 90% of them bleach, why do the other 10% not?”

So he started looking into it, and found at least one case where coral have shown a surprising resilience to the effects of climate change. In the back-reef lagoons of American Samoa, living in tide pools near the white sand beach of a tiny island are a bed of coral that may hold the key to its species’ survival. Some pools have produced the right conditions (cooler temperatures) for healthy coral, where a warmer pool nearby has bleached out.

“Some corals are stronger than others,” Palumbi said. “It’s exciting because we can understand how much they bleach when exposed to heat stress.”

Palumbi went to the islands to conduct an experiment. There he swapped healthy ‘cool pool’ coral and sick ‘warm pool’ coral. The stress of living on the edge in the warm pool, it turns out, builds up the coral’s resistance. While the cool-dwelling coral were able to adapt slightly to warmer pool conditions.

“Now we’re figuring out what we can do with this information,” he said. “Can we build coral nurseries that are heat resistant?”

And, is it sufficient to buoy the professor who notes that 30% of the world’s coral have died because of bleaching?

“As a conservation biologist, I try to look at the coming century and ask, ‘What do we hope to solve?’ If its the (carbon) emissions problem, we all have a part in it. Those of us who can dramatically reduce their CO2 emissions, should.

“Our role as scientists is to save as much as possible of the natural world. To stabilize as much as possible, and have it come back.”

After all, coral have a valuable ecological service to offer coastal communities.

“Corals are wonderful sea walls,” he concludes. “They can keep up with slow level sea rise, and they are natural sea level protections.”

Unfortunately, unless global carbon emissions can be curbed, sea levels will overtake even the massive coral reefs protecting cities and island nations that depend on them.

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