Kim Cobb, a marine scientist at the Georgia Institute of Technology, expected the coral to be damaged when she plunged into the deep blue waters off Kiritimati Island, a remote atoll near the center of the Pacific Ocean. Still, she was stunned by what she saw as she descended some 30 feet to the rim of a coral outcropping.
“The entire reef is covered with a red-brown fuzz,” Dr. Cobb said when she returned to the surface after her recent dive. “It is otherworldly. It is algae that has grown over dead coral. It was devastating.”
The damage off Kiritimati is part of a mass bleaching of coral reefs around the world, only the third on record and possibly the worst ever. Scientists believe that heat stress from multiple weather events including the latest severe El Niño, compounded by climate change, has threatened more than a third of Earth’s coral reefs. Many may not recover.
Coral reefs are the crucial incubators of the ocean’s ecosystem, providing food and shelter to a quarter of all marine species, and they support fish stocks that feed more than one billion people. They are made up of millions of tiny animals, called polyps, that form symbiotic relationships with algae, which in turn capture sunlight and carbon dioxide to make sugars that feed the polyps.
An estimated 30 million small-scale fishermen and women depend on reefs for their livelihoods, more than one million in the Philippines alone. In Indonesia, fish supported by the reefs provide the primary source of protein.
“This is a huge, looming planetary crisis, and we are sticking our heads in the sand about it,” said Justin Marshall, the director of CoralWatch at Australia’s University of Queensland.
Bleaching occurs when high heat and bright sunshine cause the metabolism of the algae — which give coral reefs their brilliant colors and energy — to speed out of control, and they start creating toxins. The polyps recoil. If temperatures drop, the corals can recover, but denuded ones remain vulnerable to disease. When heat stress continues, they starve to death.
Damaged or dying reefs have been found from Réunion, off the coast of Madagascar, to East Flores, Indonesia, and from Guam and Hawaii in the Pacific to the Florida Keys in the Atlantic.
The largest bleaching, at Australia’s Great Barrier Reef, was confirmed last month. In a survey of 520 individual reefs that make up the Great Barrier Reef’s northern section, scientists from Australia’s National Coral Bleaching Task Force found only four with no signs of bleaching. Some 620 miles of reef, much of it previously in pristine condition, had suffered significant bleaching.
In follow-up surveys, scientists diving on the reef said half the coral they had seen had died. Terry Hughes, the director of the Center of Excellence for Coral Reef Studies at James Cook University in Queensland, who took part in the survey, warned that even more would succumb if the water did not cool soon.
The Latest on: Coral bleaching
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The Latest on: Coral bleaching
- Scientists use loudspeakers to make dead coral reefs sound healthy, and fish flock to themon December 1, 2019 at 7:51 am
Severe coral bleaching triggered by extreme heat waves killed off 50 percent of the Great Barrier Reef, the planet’s largest coral reef, in 2016 and 2017. Such bleaching events – which occur when the ...
- Underwater Speakers Help Revive Dying Coral Reefs, Study Findson November 30, 2019 at 3:35 pm
Several factors are leading to the increased deaths of coral reefs globally. A recent study found that the primary factor in the death of corals in the Florida Keys is due to nitrogen enrichment from ...
- Damaged coral reefs could be restored using underwater loudspeakerson November 30, 2019 at 1:44 pm
According to a study published earlier this year, baby coral in the Great Barrier Reef have declined by 89% due to mass bleaching in 2016 and 2017. Deadly back-to-back bleaching events have devastated ...
- Underwater speakers could help revive ailing coral reefs, study showson November 30, 2019 at 11:44 am
But rising water temperatures set off a process of coral bleaching, in which the algae is released and the reef loses its main energy source. Ocean acidification is another source of our coral reef ...
- A New Disease Is Turning Corals Greyon November 30, 2019 at 6:04 am
When a coral is infected with this disease, a grey film of cyanobacteria overtakes the coral’s tissue. It changes the microbial community of the affected corals and appears to occur after corals ...
- Dying coral could be revived by playing sounds of healthy reefs via underwater loudspeakerson November 29, 2019 at 3:56 am
Healthy coral reefs are remarkably noisy places — the crackle of ... The loss of the algae causes them to bleach and turn white. This bleached states can last for up to six weeks, and while corals can ...
- Resilient coral could pass down their heat-resistance to the next generationon November 27, 2019 at 10:25 am
Coral “bleaching” occurs when environmental stressors like warm waters disrupt this balance. But some coral might be extra adaptable. Music by https://audionautix.com/ (Video from The ...
- Coral Reefs Face New Threat From Grey-Patch Diseaseon November 21, 2019 at 4:00 pm
In the midst of climate change, coral reefs have experienced an increase in so-called bleaching events that lead to coral disease and subsequent infections. As a result, once abundant coral reefs are ...
- Researchers shed light on modulation of thermal bleaching of coral reefs by internal waveson November 20, 2019 at 9:30 am
Coral reefs around the world are threatened by pan-tropical bleaching events that occur when the surrounding sea water temperatures increase due to ongoing climate change and extreme conditions like ...
- Hawaii Researchers Investigate The How And Why Of Coral Reef Bleachingon November 18, 2019 at 8:56 am
Record-breaking temperatures in Hawaii this past summer may lead to unprecedented coral bleaching. It's caused by changes in water temperature, light or nutrients, and it can kill coral. Scientists on ...
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