World's oceans facing biggest coral die-off in history, scientists warn

A third global bleaching of coral reefs is underway following a massive and persistent underwater heatwave
A strong El Niño is set to worsen the plight of coral in 2016.
Karl Mathiesen The Guardian 8 Oct 15;

Scientists have confirmed the third-ever global bleaching of coral reefs is under way and warned it could see the biggest coral die-off in history.

Since 2014, a massive underwater heatwave, driven by climate change, has caused corals to lose their brilliance and die in every ocean. By the end of this year 38% of the world’s reefs will have been affected. About 5% will have died forever.

But with a very strong El Niño driving record global temperatures and a huge patch of hot water, known as “the Blob”, hanging obstinately in the north-western Pacific, things look far worse again for 2016.

For coral scientists such as Dr Mark Eakin, the coordinator of the US National Oceanic and Atmospheric Administration Coral Reef Watch programme, this is the cataclysm that has been feared since the first global bleaching occurred in 1998 .

“The fact that 2016’s bleaching will be added on top of the bleaching that has occurred since June 2014 makes me really worried about what the cumulative impact may be. It very well may be the worst period of coral bleaching we’ve seen,” he told the Guardian.

The only two previous such global events were in 1998 and 2010, when every major ocean basin experienced bleaching.

Professor Ove Hoegh-Guldberg, director of the Global Change Institute at the University of Queensland, Australia, said the ocean was now primed for “the worst coral bleaching event in history”.

“The development of conditions in the Pacific looks exactly like what happened in 1997. And of course following 1997 we had this extremely warm year, with damage occurring in 50 countries at least and 16% of corals dying by the end of it,” he said. “Many of us think this will exceed the damage that was done in 1998.”

After widespread devastation was confirmed in the Caribbean this month, a worldwide consortium of coral scientists joined on Thursday to sombrely announce the third-ever global bleaching event – and warn of a tenuous future for the precious habitat unless sharp cuts were made to carbon emissions.

Since the early 1980s the world has lost roughly half of its coral reefs. Hoegh-Guldberg said the current event was directly in line with predictions he made in 1999 that continued global temperature rise would lead to the complete loss of coral reefs by the middle of this century.

“It’s certainly on that road to a point about 2030 when every year is a bleaching year … So unfortunately I got it right,” he said.

Hoegh-Guldberg said he had personally observed the first signs of bleaching on Australia’s Great Barrier Reef in the past fortnight, months before the warm season begins. He said the warming pattern indicated bleaching this summer would likely affect 50% of the reef, leaving 5-10% of corals dead. Eakin said seeing bleaching on the reef at this time of year was “disturbing”.

“We are going to have to double our efforts to reduce the other threats to the reef,” said Hoegh-Guldberg of the icon that Unesco has considered listing as World Heritage in Danger, due to the threats of a mooted coal port expansion, agricultural run-off and climate change. “It’s like a hospital patient. If you’ve got a chronic disease then you are more sensitive to a lot of other things and if you want a recovery then you need to take all those other stresses off.”

The difference between this bleaching event and others before it is not just the extremity of sea temperatures, but how long they have persisted for. Corals can recover from bleaching if the temperature relents. But after a month or more the organisms that build these brilliantly coloured underwater cities die.

“This is not only a big event, but it’s more persistent than any of our past ones, including 1998,” said Eakin. In many areas the bleaching has now lasted far longer than the threshold month and in Hawaii, Guam, Kiribati and Florida there has been back-to-back bleaching events across the past two years.

Like rainforests on land, coral reefs are home to a riot of biodiversity. On just 0.1% of the ocean’s floor they nurture 25% of the world’s marine species. The impact of losing this would be devastating for the 500 million people who rely on coral ecosystems for their food and livelihood. These effects would not be felt immediately, but over the coming years as fish species move on or die off.

“It really does affect things like tourism and fishing,” said Hoegh-Guldberg. However, he said there was still hope, if governments acted immediately to relieve both global and local pressures on reefs.

“If we were to take strong action on the emission issue and we were to take strong action on the non-climate issues such as overfishing and pollution, reefs would rebound by mid to late century,” he said.


NOAA declares third ever global coral bleaching event
Bleaching intensifies in Hawaii, high ocean temperatures threaten Caribbean corals
NOAA HEADQUARTERS EurekAlert 8 Oct 15;

As record ocean temperatures cause widespread coral bleaching across Hawaii, NOAA scientists confirm the same stressful conditions are expanding to the Caribbean and may last into the new year, prompting the declaration of the third global coral bleaching event ever on record.

Waters are warming in the Caribbean, threatening coral in Puerto Rico and the U.S. Virgin Islands, NOAA scientists said. Coral bleaching began in the Florida Keys and South Florida in August, but now scientists expect bleaching conditions there to diminish.

"The coral bleaching and disease, brought on by climate change and coupled with events like the current El Niño, are the largest and most pervasive threats to coral reefs around the world," said Mark Eakin, NOAA's Coral Reef Watch coordinator. "As a result, we are losing huge areas of coral across the U.S., as well as internationally. What really has us concerned is this event has been going on for more than a year and our preliminary model projections indicate it's likely to last well into 2016."

While corals can recover from mild bleaching, severe or long-term bleaching is often lethal. After corals die, reefs quickly degrade and the structures corals build erode. This provides less shoreline protection from storms and fewer habitats for fish and other marine life, including ecologically and economically important species.

This bleaching event, which began in the north Pacific in summer 2014 and expanded to the south Pacific and Indian oceans in 2015, is hitting U.S. coral reefs disproportionately hard. NOAA estimates that by the end of 2015, almost 95 percent of U.S. coral reefs will have been exposed to ocean conditions that can cause corals to bleach.

The biggest risk right now is to the Hawaiian Islands, where bleaching is intensifying and is expected to continue for at least another month. Areas at risk in the Caribbean in coming weeks include Haiti, the Dominican Republic and Puerto Rico, and from the U.S. Virgin Islands south into the Leeward and Windward islands.

The next concern is the further impact of the strong El Niño, which climate models indicates will cause bleaching in the Indian and southeastern Pacific Oceans after the new year. This may cause bleaching to spread globally again in 2016.

"We need to act locally and think globally to address these bleaching events. Locally produced threats to coral, such as pollution from the land and unsustainable fishing practices, stress the health of corals and decrease the likelihood that corals can either resist bleaching, or recover from it," said Jennifer Koss, NOAA Coral Reef Conservation Program acting program manager. "To solve the long-term, global problem, however, we need to better understand how to reduce the unnatural carbon dioxide levels that are the major driver of the warming."

This announcement stems from the latest NOAA Coral Reef Watch satellite coral bleaching monitoring products, and was confirmed through reports from partner organizations with divers working on affected reefs, especially the XL Catlin Seaview Survey and ReefCheck. NOAA Coral Reef Watch's outlook, which forecasts the potential for coral bleaching worldwide several months in the future, predicted this global event in July 2015.

The current high ocean temperatures in Hawaii come on the heels of bleaching in the Main Hawaiian Islands in 2014?only the second bleaching occurrence in the region's history?and devastating bleaching and coral death in parts of the remote and well-protected Papahānaumokuākea Marine National Monument in the Northwestern Hawaiian Islands.

"Last year's bleaching at Lisianski Atoll was the worst our scientists have seen," said Randy Kosaki, NOAA's deputy superintendent for the monument. "Almost one and a half square miles of reef bleached last year and are now completely dead."

Coral bleaching occurs when corals are exposed to stressful environmental conditions such as high temperature. Corals expel the symbiotic algae living in their tissues, causing corals to turn white or pale. Without the algae, the coral loses its major source of food and is more susceptible to disease.

The first global bleaching event was in 1998, during a strong El Niño that was followed by an equally very strong La Niña. A second one occurred in 2010.

Satellite data from NOAA's Coral Reef Watch program provides current reef environmental conditions to quickly identify areas at risk for coral bleaching, while its climate model-based outlooks provide managers with information on potential bleaching months in advance.

The outlooks were developed jointly by NOAA's Satellite and Information Service and the National Centers for Environmental Prediction through funding from the Coral Reef Conservation Program and the Climate Program Office.

For more information on coral bleaching and these products, visit: http://www.coralreefwatch.noaa.gov/satellite/index.php.

NOAA Press Release dated 8 Oct 15http://www.noaanews.noaa.gov/stories2015/100815-noaa-declares-third-ever-global-coral-bleaching-event.html

Corals worldwide hit by bleaching
Warm ocean waters combine with El Niño to turn reefs a stark white.
Alexandra Witze Nature 8 Oct 15;

From Hawaii to Papua New Guinea to the Maldives, coral reefs are bleaching — in so many regions that the US National Oceanographic and Atmospheric Administration (NOAA) officially declared a global bleaching event on 8 October. The event, the third in recorded history, is expected to grow worse in coming months.

Warm ocean temperatures, linked to climate change and a strengthening El Niño weather pattern, have triggered reefs to expel the algae that colour them. Reefs in parts of the Pacific, the Indian and the Atlantic oceans have now turned white. By the end of the year, the bleaching could affect more than a third of the world’s coral reefs and kill more than 12,000 square kilometres of them, NOAA estimates.

“We’re in shock and awe of what’s happening,” says Ove Hoegh-Guldberg, a marine scientist at the University of Queensland in Brisbane, Australia. “It’s a doozy of an event.”

Bleached corals are more vulnerable to stressors such as disease that can kill them. In 1998, the biggest bleaching event in history led to the death of 16% of the world’s coral reefs.

Poor prognosis

The current event began in 2014 in parts of the Pacific — including the Hawaiian Islands, which experienced mass coral bleaching around multiple islands. Global ocean temperatures last year were nearly 0.6 degrees Celsius higher than the twentieth-century average, a record high. “We came into 2015 with very warm oceans, and now we have a full-formed El Niño coming,” says Mark Eakin, coordinator of NOAA’s Coral Reef Watch programme, run out of Washington DC.


Source: NOAA
This map shows areas at highest risk of bleaching from now until January 2016.

To top it all off, a warm mass of water dubbed 'the blob' has been shuttling back and forth across the northern Pacific for the past several months, also helping to keep temperatures high. (It is unclear whether the blob is linked to climate change or other large-scale atmospheric patterns.)

“The temperatures we’re seeing are anomalies, and have the potential to dramatically impact the integrity of reefs around the world,” says Ruth Gates, a marine biologist at the Hawaii Institute of Marine Biology in Kaneohe.

NOAA models suggest that by mid-2016, the bleaching will have spread even further through most of the world’s coral-bearing regions, extending across nearly all of the Indian Ocean and the South Pacific.

NOAA uses data on sea-surface temperature, gathered by its Polar-orbiting Operational Environmental Satellites, to produce global maps depicting where waters are warm enough to trigger bleaching. Local marine scientists, volunteers and others — under the umbrella of monitoring groups such as Reef Check in Marina del Rey, California — then go out to inspect the conditions where bleaching may be happening.

Private eyes

A privately funded venture, the XL Catlin Seaview Survey, has been mapping reefs in 26 countries since 2012. Among other technologies, it uses a high-resolution camera attached to an underwater scooter to quickly compile 360-degree images of reefs.

This effort should help scientists to document mass bleaching during the present event better than during the last one, which happened in 2010. The Global Coral Reef Monitoring Network, an international government-based initiative, was reorganized in 2008 and shifted from gathering data on reefs to preparing reports on the basis of data from others. As a result, there was not a full network in place during 2010 to monitor coral status, Eakin says. “We’re not going to let this one slip by,” he adds.

Marine scientists need to document long-term changes to corals in many regions to understand how reefs might survive bleachings, says Gates. In a bay off the island of Oahu in Hawaii, some corals that experienced bleaching in 2014 surprisingly managed to reproduce this year, even with back-to-back bleachings. And earlier this year, a Nature paper1 reported that 12 out of 21 reefs studied in the Seychelles managed to mostly recover after the devastating bleaching of 1998.

But Hoegh-Guldberg notes that bleaching events may now be coming too quickly, giving corals no time to recover between them. “Reefs, like rainforests, take time,” he says. And other factors, such as ocean acidification, are also stressing corals to the point that decades from now, reef communities will look and function much differently than they do today, says Cheryl Logan, a marine biologist at California State University, Monterey Bay, in Seaside.

Nature doi:10.1038/nature.2015.18527

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