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
- Ocean deoxygenation: A silent driver of coral reef demise?on April 1, 2020 at 6:33 am
"Oxygen fundamentally sustains reef life. "It's possible that declining oxygen availability has amplified, and will continue to amplify, the impact of catastrophic events such as heat-wave driven mass ...
- Climate crisis may have pushed world's tropical coral reefs to tipping point of 'near-annual' bleachingon March 31, 2020 at 9:30 am
Mass bleaching seen along Great Barrier Reef could mark start of global-scale event, expert warns ...
- How coral bleaching affects reef fishon March 31, 2020 at 8:10 am
While we don’t know if fish populations declined from the 2016 bleaching disaster, one 2018 study did show the types of fish species on some coral reefs changed. Our study dug deeper into fish DNA. I ...
- I studied what happens to reef fish after coral bleaching. What I saw still makes me nauseouson March 26, 2020 at 7:13 pm
Jodie L. Rummer receives funding from the Australian Research Council. While we don’t know if fish populations declined from the 2016 bleaching disaster, one 2018 study did show the types of fish ...
- Great Barrier Reef suffers mass coral bleaching due to heat stresson March 26, 2020 at 12:12 pm
The Great Barrier Reef is experiencing another "mass bleaching event," according to Marine Park Authority. The government agency said that the widespread bleaching was caused by the high temperatures ...
- Mass Coral Bleaching Found in Great Barrier Reefon March 26, 2020 at 6:29 am
SYDNEY, Australia (AFP) — Australia’s Great Barrier Reef has suffered “very widespread” damage after rising sea temperatures caused the third mass coral bleaching events in five years, authorities ...
- Great Barrier Reef suffers mass coral bleaching eventon March 26, 2020 at 2:57 am
Australia's Great Barrier Reef has suffered "very widespread" damage after rising sea temperatures caused the third mass coral bleaching events in five years, authorities said Thursday. The planet's l ...
- Great Barrier Reef’s latest bleaching confirmed by marine park authorityon March 26, 2020 at 1:32 am
The government agency responsible for the Great Barrier Reef has confirmed the natural landmark has suffered a third mass coral bleaching episode in five years, describing the damage as “very ...
- Great Barrier Reef suffers third mass coral bleaching in five yearson March 25, 2020 at 11:38 pm
Australia's Great Barrier Reef has likely experienced its most widespread bleaching event on record, according to a U.S. government scientist who monitors the world's coral reefs. This marks the third ...
- Great Barrier Reef suffers third mass bleaching in five yearson March 25, 2020 at 11:24 pm
Australia's Great Barrier Reef has suffered another mass bleaching event - the third in just five years. Warmer sea temperatures - particularly in February - are feared to have caused huge coral loss ...
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