Great Barrier Reef NOT DEAD! – Yet

At about the same moment that millions of Americans sat staring at their television or laptop or phone—watching the results from the presidential election stream in, seeing state after state called for Donald Trump—Kim Cobb was SCUBA diving near the center of the Pacific Ocean. She did not watch the same trickle of news as other Americans. She surfaced, heard the results, and dove in the water again. She was, after all, attending to devastation.Cobb is a climate scientist at the Georgia Institute of Technology. On November 8, she was on her most recent of many research trips to Kiritimati Island reef, the largest coral atoll in the world. (Kirimati is pronounced like Christmas.) She first began studying the reef in 1997, during the last big El Niño warming event; she has returned nearly every year since. Last year, she went three times.“We had been waiting for the big one. And boy… did it happen,” she told me earlier this year. “It really rolled out at an unprecedented magnitude. This particular El Niño event had its maximum temperature loading almost in a bulls-eye almost around Kirimati Island.”

By any measure, its caused a cataclysm. Eighty-five percent of the corals in the reef died: They will never recover, disintegrating into sand over the next several years. Two-thirds of the surviving corals bleached in some way, meaning they did not reproduce and may have sustained long-term damage.“Almost none of this reef has made it through 2015 and 2016,” Cobb said, calling the event “the wholesale destruction of the reef.”By any measure, 2016 was not a good year for coral reefs. El Niño raised ocean temperatures worldwide, devastating corals the world over. The Great Barrier Reef—the sprawling system off the coast of Australia, and among the world’s  most biodiverse reef systems—suffered a particularly debilitating year. Miles and miles of the coral reef bleached so severely, and for so long, that they died.

On Monday, news broke that it happened again. For the second year in a row, warm ocean temperatures are bleaching the Great Barrier Reef. The white splotches of ocean floor indicative of the phenomenon run even farther south—some 500 kilometers—than they did last year. The bleaching occurred even though there is no worldwide El Niño this year: The reef is ailed not by a rare climatic phenomenon but by the baseline warming of the oceans.

Until this decade, back-to-back bleaching events like that simply didn’t happen.

“It’s new. It is so new. It’s a complete change in the phenomenon that all of us study,” said Ruth Gates, a professor at the Hawaii Institute of Marine Biology and the president of the International Society for Reef Studies. “We knew that this day would come—we’ve been seeing the thermal-tolerance threshold for corals get closer and closer, and we knew it was pushing over the limit for coral survival.”

“There will now be years where it doesn’t take an El Niño event to reach the bleaching threshold. This is going to be statistically more likely in a warming world,” said Cobb.The intensity and duration of bleaching events is ultimately leading to a change in the study of coral reefs overall. Instead of focusing on reefs in situ, scientists are increasingly having to study how reefs recover from warming oceans and other forms of environmental disaster.“We are in a different moment with coral reefs right now. We’ve had this global insult on reefs. The choice now is to study recovery because that’s what we are doing, because that’s what we have to do,” said Gates.

The reef that Gates knows best—the coral reef in Kāne’ohe Bay, right next to the institute where she works—was one of the first in the world to suffer a back-to-back bleaching. In 2014, a warming Pacific pushed the Kāne’ohe Bay corals to warm; in 2015, the sea bleached them again. “We were not really expecting it to be a bleaching year then and we didn’t expect it to be a bleaching year the following year,” she told me.

Since then, she has been monitoring the health of the reef and watched it recover. Scientists still don’t know how repeated bleaching events—especially in back-to-back years—will affect the long-term health of a coral reef. Kāne’ohe Bay has recovered faster and more vigorously than Gates expected, but it is a considerably less biodiverse reef than the Great Barrier Reef. Much of Gates’ research focuses on expanding coral resilience between reefs. (There was a wonderful New Yorker profile on her work last year.)

Cobb, meanwhile, is organizing research into how Kirimati Island bounces back from the El Niño bleaching. Thankfully, Kirimati has been slightly cooler than normal over the last few months, and baby corals have already begun to sprout in the reef.  “We’ll see in out years as a team of climate scientists, ecologists, and oceanographers focus on this island,” she told me. “We plan on witnessing its recovery in its various stages and trying to see how it differs from the reef that was there before this event.”This represents another major step forward for the field. When Gates started her doctoral research in the 1980s, scientists were still beginning to understand that coral bleaching can occur in the first place. Now, they know it is triggered in large part by temperature changes.The devastation to coral reefs will continue as climate change runs apace.  The International Society for Reef Studies predicts that 90 percent of coral reefs worldwide will be at risk of destruction by 2050. (This stands out: Many really dire predictions of severe climate damage start after 2050.)

“We are just one species that are in line to be hit very heavily by climate change,” said Gates. “Coral reefs are in the front line but they’re telling us something very important.”

https://youtu.be/4p_YXKT5qWU

https://youtu.be/9ZlJm3IBTEo

Deeper down, are coral reefs holding up better?

The next time you see a picture of a coral reef bleached ghost-white by warming seas, remember that there’s a good chance it was taken in the photic zone: the brightly lit layer of water that extends about 50 meters below the surface.

Australian marine biologist Tom Bridge wants to shift our focus deeper. Speaking at the World Science Festival in Brisbane, Australia, on Friday, he pointed out that two-thirds of all coral lives in the 50- to 700-meter (165 to 2,300 feet) range. That’s a habitat that reaches deeper than the height of New York’s One World Trade Center.

In particular, he wants to call our attention to the “mesophotic zone,” between 50 to 150 meters (165 to 492 feet), where enough sunlight reaches to sustain many of the same corals found higher up. “We have this sort of intermediate zone between the 50 to 150 meter depth range that’s really been ignored for a long period of time,” Dr. Bridge, the senior curator at Queensland Museum in Brisbane told the World Science Festival audience.

Studying this zone could do more than just fill a gap in scientific knowledge. The mesophotic’s greater depth and colder temperatures provide a buffer against climate change and other well-known threats facing reefs and studying it could change scientific methods for protecting the reefs overall.

“Sometimes these deeper areas are less vulnerable to these disturbances than shallow water habitats,” Bridge explained. In oceans, a transition layer called the “thermocline” separates warmer and colder waters. During one mesophotic research dive in Hawaii, recently described in Science magazine, the team reached waters as cold as 10 degrees Celsius, or 50 degrees F.

Along with the cold temperatures, scientists have other good reasons to stay in the shallows. Standard diving protocol involves pausing at regular intervals during an ascent.

To make enough time for these pauses, divers who go deep typically use a rebreather, which re-circulates exhaled air, rather than breathe compressed air from a scuba tank. Even then, a research dive at 100 meters (328 feet) might involve 20 minutes of work on the reef, followed by two hours of stops on the way up.

Despite the challenges, Bridge thinks studying the mesophotic could offer a more holistic – and encouraging – picture of Earth’s reefs. The same temperatures that chill divers to the bone could protect the mesophotic’s corals from the bleaching that occurs closer to the surface. They’re also farther removed from other threats, such as overfishing and coastal development.

Understanding if these traits make the mesophotic stronger would take more research. “Compared to what we know about shallow coral reefs, everything in the deep coral reefs is a big question mark,” Richard Pyle, an associate zoologist at Bishop Museum in Honolulu who specializes in deep-water coral climate, told Science magazine.

Bridge wants that to change. “A lot of the time it’s out of sight, out of mind…. If you can’t see it, it doesn’t become included in conservation plans and things like that.”

 

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