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World's coral reefs face mass bleaching event next year: Disaster due to El Niño 'could be worst ever recorded'

It is only the third recorded global bleaching event in history, with areas such as Australia's Great Barrier Reef set to be hard hit
Study warns that the disaster could affect 38% of the world's coral reefs and destroy 4,600 square miles (12,000 square kilometres) of reef
'If conditions continue to worsen, the Great Barrier Reef is set to suffer widespread bleaching and subsequent mortality,' one scientist warned

Published: 04:15 EST, 8 October 2015 | Updated: 13:02 EST, 8 October 2015

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The world faces a mass global coral bleaching even next year driven by the warming effects of the El Niño weather phenomenon - and it could be the worst on record, scientists have warned.

It would be only the third recorded global bleaching event in history, with areas such as Australia's Great Barrier Reef set to be hard hit.

The Barrier Reef - the world's biggest coral reef ecosystem - is already struggling from the threat of climate change, as well as farming run-off, development and the coral-eating crown-of-thorns starfish.

'If conditions continue to worsen, the Great Barrier Reef is set to suffer from widespread coral bleaching and subsequent mortality, the most common effect of rising sea temperatures,' said Ove Hoegh-Guldberg of the University of Queensland (fish swimming on Australia's Great Barrier Reef pictured)

'If conditions continue to worsen, the Great Barrier Reef is set to suffer from widespread coral bleaching and subsequent mortality, the most common effect of rising sea temperatures,' said the University of Queensland's Global Change Institute director Ove Hoegh-Guldberg.

'In the first major global event in 1998, more than half the Great Barrier Reef experienced bleaching with about five to 10 per cent of the corals dying.

'Thankfully the Great Barrier Reef was spared during this second global event [in 2010] due to storm activity which alleviated the heat stress. The reef may not be so lucky in 2016.'

A glimpse into the future? A before and after image of the bleaching in American Samoa. The image on the left was taken in December 2014 and the image on the right was taken in February 2015 when the XL Catlin Seaview Survey responded to a NOAA coral bleaching alert

The Great Barrier Reef narrowly avoided being put on the UN World Heritage in danger list this year with Canberra now working on a plan to improve the reef's health over successive decades (stock image pictured)

The study was carried out by the University of Queensland and the US National Oceanic Atmospheric Administration.

It warns that the disaster could affect 38 per cent of the world's coral reefs and destroy 4,600 square miles (12,000 square kilometres) of reef.

The Great Barrier Reef narrowly avoided being put on the UN World Heritage in danger list this year with Canberra now working on a plan to improve the reef's health over successive decades.

Bleaching is a phenomenon that turns corals white or fades their colour, threatening a valuable source of biodiversity, tourism and fishing.

2015's EL NINO COULD BE STRONGEST EVER RECORDED

The current El Nino weather phenomenon is expected to peak between October and January and could turn into one of the strongest on record, experts from the World Meteorological Organization have warned.

Climate models and experts suggest surface waters in the east-central Pacific Ocean are likely to be more than 2 degrees hotter than average, potentially making this El Nino one of the strongest ever.

Typically, the warm air above the eastern Pacific is causing increased precipitation over the west coast of South America and dry conditions over the Australia/Indonesia archipelago and the Southeast Asia region, said Maxx Dilley, director of the WMO's Climate Prediction and Adaptation Branch.

Pictured is a comparison of sea surface height in the Pacific as measured at the end of July in 1997 and 2015. Comparing the two years, 1997 seems slightly less intense. But trade winds collapsed and the eastern Pacific warmed dramatically from August through November 1997, setting the stage for a turbulent winter

Dilley said: 'we have a well-established El Nino event under way,' and farmers, rescue officials and reservoir operators would be among officials bracing for its rise.

El Nino can also bring higher rainfall and sometimes flooding to the Horn of Africa, but causes drier conditions in southern Africa, Dilley said.

'A mature and strong El Niño is now present in the tropical Pacific Ocean,' the WMO said.

Climate scientists are better prepared than ever with prediction models and data on El Nino patterns, but the impact of this El Nino in the northern hemisphere is hard to forecast because there is also an Arctic warming effect at work on the Atlantic jetstream current.

It occurs when reef symbiosis - the mutually beneficial relationship between two organisms that inhabit corals - is disrupted by a rise in ocean warming, although there can also be other causes.

Oceans absorb approximately 93 per cent of the increase in Earth's heat from climate change, making them one of the most visual indicators of the issue – particularly when change is revealed through dramatic episodes like global coral bleaching.

MARINE LIFE HAS 'HALVED IN 45 YEARS', SAY SCIENTISTS

The number of fish, turtles and other wildlife in the world's oceans has halved in decades, conservationists warn.

Overfishing, pollution and changing climate are blamed for the 'potentially catastrophic' decline in marine life.

From the temperate UK waters to tropical coral reefs, the planet's seas are emptying fast, the World Wildlife Fund and the Zoological Society of London say.

Species in crisis range from leatherback turtles, 'monsters of the deep' that can be seen off the coast of Britain, to the colourful corals of the Great Barrier Reef.

The Living Blue Planet report tracks the fate of more than 1,200 species of marine mammals, birds, fish and reptiles since 1970. It found a 49 per cent drop in numbers among the 6,000 populations studied around the world.

Some declines were even more dramatic, with populations of the Scombridae family of fish, which includes tuna and mackerel, falling by 74 per cent.

Sea cucumbers – animals shaped like the vegetable that are prized as a luxury food but play a vital role in improving water quality – have all but disappeared from the Red Sea. And Australia's Great Barrier Reef has lost more than half of its coral in the last 30 years.

Worldwide, one in four species of shark, ray and skate is threatened with extinction. The porbeagle shark, a favourite with UK anglers, has undergone a 'precipitous decline', as has the leatherback turtle. Other species in peril in British waters include puffins, sand eels and sole.

During a bleaching event, corals expel the golden-brown algae that grow within their body tissue, exposing their white skeletons - hence the term 'bleaching.'

If the ocean temperature remains higher than the seasonal norm for a number of weeks the corals can die en masse, causing the loss of some corals that may be decades to centuries old.

Bleaching can transform healthy coral reefs into reefs dominated by other organisms such as seaweeds. This can take decades to reverse and will only happen if conditions become hospitable for corals again.

One of the worst episodes on record, which affected reefs in 60 tropical countries, took place in 1998, when the El Nino weather pattern was exceptionally strong.

The phenomenon occurs when trade winds that circulate over waters in the tropical Pacific start to weaken and sea surface temperatures rise.

US government scientists in August said the El Nino currently under way - the first in five years - could be among the strongest in 65 years, while authorities in Australia have predicted it would be 'strong' and 'substantial'.

Corals depend on single-cell algae called dinoflagellates that live in vast colonies on their surface.

The dinoflagellates feed on nitrogen, phosphorus and other nutrients provided by the coral and use light to transform this food into energy.

The photosynthesis also releases energy into the tissues of the coral, enabling it to build the calcium skeleton which houses the dinoflagellates.

When corals come under stress, such as from significantly warmer seas, they expel the dinoflagellates.

They then turn visibly pale, as the algae have the pigments which give the skeletons their distinctive colour.

The reefs are not dead at this point. But they become more susceptible to disease and will die if they fail to regain their plankton friends.

Hoegh-Guldberg said research he conducted in 1999 predicted mass coral bleaching events would become successively worse over time if the world failed to deal with rising atmospheric gases.

'Unfortunately, 16 years later, these predictions are beginning to unfold,' he said.

The warning comes just months ahead of a UN-led conference in Paris which aims to seal a wide-ranging agreement to limit the worst effects of climate change.

It hopes to crown a six-year effort by 195 nations with a post-2020 pact on curbing greenhouse gases.