Coral reefs are being rapidly killed off by global warming

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If CO2 levels continue to rise the consequences will be


The devastating impact of global warming on ocean life has been laid bare in a shocking new scientific report.

Coral reefs across the globe are being killed off by a combination of increasing temperatures and ocean acidification caused by rising carbon dioxide (CO2) levels.

Researchers found blooms of algae are blanketing the seabed in areas of high CO2 concentration, choking corals and lowering marine diversity.

If CO2 levels continue to rise at their current rate, the consequences will be ‘catastrophic’, scientists have warned.

In the latest report, experts warned that the only way to reverse the trend is to meet global warning reduction targets.

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If CO2 levels continue to rise the consequences will be ‘catastrophic’, scientists have warned. At a site with a CO2 concentration of 900ppm, corresponding to conditions predicted for 2100, the high CO2 favors the growth of low profile algae (pictured)

Teams of British, Italian and Japanese researchers, including from the University of Plymouth, found a worrying lack of corals in areas of the Pacific where CO2 levels met present-day averages.

In contrast, marine areas with pre-industrial levels of CO2 flourished with corals and other species and sea-life. 

Experts discovered the stark contrast by analysing volcanic CO2 seeps off Shikine Island, in Japan, where ocean currents cause CO2 levels to mimic those before the industrial revolution.

Professor Jason Hall-Spencer, a marine biologist at the University of Plymouth, said: ‘Our research site is like a time machine.

‘In areas with pre-Industrial levels of CO2 the coast has an impressive amount of calcified organisms such as corals and oysters.

‘But in areas with present-day average levels of surface seawater CO2 we found far fewer corals and other calcified life, and so there was less biodiversity.

‘It shows the extensive damage caused by humans due to CO2 emissions over the past 300 years and unless we can get a grip on reducing CO2 emissions we will undoubtedly see major degradation of coastal systems worldwide.’

Teams of Scuba divers carried out studies along underwater CO2 gradients, created by volcanic seeps, recording how sea life responds to acidification.

The devastating impact of global warming on ocean life is laid bare by a shock new report. Coral reefs (pictured) are being rapidly killed off by a combination of rising temperatures and ocean acidification caused by industrial carbon dioxide, it found

The devastating impact of global warming on ocean life is laid bare by a shock new report. Coral reefs (pictured) are being rapidly killed off by a combination of rising temperatures and ocean acidification caused by industrial carbon dioxide, it found

WHAT DID THE UNIVERSITY OF PLYMOUTH DISCOVER ABOUT CORAL REEFS? 

Teams of British, Italian and Japanese researchers, including from the University of Plymouth, found a worrying lack of corals in areas of the Pacific where CO2 levels met present-day averages. 

Scuba divers carried out studies along underwater CO2 gradients, created by volcanic seeps, recording how sea life responds to acidification.

They found only a few plant species benefitted from the changing conditions.

But they were mainly smaller weeds and algae that blanket the seabed, choking corals and lowering overall marine diversity.

These species, and some smaller marine animals, thrive because they are more tolerant to the stress posed by rising levels of CO2, the researchers explained. 

The only way to reverse the trend is to meet global warning reduction targets, the scientists added.

They found only a few plant species benefitted from the changing conditions.

However, these were mainly smaller weeds and algae that blanket the seabed, choking corals and lowering overall marine diversity.

These species – as well as some smaller marine animals – thrive because they are more tolerant to the stress posed by rising levels of CO2, the researchers explained.

Lead author Dr Sylvain Agostini said: ‘These CO2 seeps provide a vital window into the future.

‘There was mass mortality of corals in the south of Japan last year, but many people cling to the hope that corals will be able to spread north.

‘Therefore it is extremely worrying to find that tropical corals are so vulnerable to ocean acidification, as this will stop them from being able to spread further north and escape the damage caused by water that is too hot for them.’

The only way to reverse the trend is to meet global reduction targets, the scientists added.

By some estimates, oceans have become 30 per cent more acidic since the Industrial Revolution, which started around 1760. 

If CO2 emissions continue at their current rate, by 2100, experts predict that acidity will increase by about 150 per cent.

Co-author Professor Kazuo Inaba said: ‘Local fishermen are keen to know how ocean acidification will affect their livelihoods.

‘Currents flowing past Japan bring waters that have naturally low levels of CO2 and fish benefit from the array of calcified habitats around our islands.

‘If we are able to meet the Paris Agreement targets to limit emissions we should be able to limit further damage to kelp forests, coral reefs and all marine ecosystems.’

The findings were published in the Nature journal Scientific Reports.

Experts discovered the stark contrast by analysing volcanic CO2 seeps off Shikine Island, in Japan, where ocean currents cause CO2 levels to mimic those before the industrial revolution

Experts discovered the stark contrast by analysing volcanic CO2 seeps off Shikine Island, in Japan, where ocean currents cause CO2 levels to mimic those before the industrial revolution

Experts said diving around Shikine Island was 'like a time machine' and allowed them to check the impact of changing CO2 levels on marine life and coral reefs. By some estimates, oceans have become 30% more acidic since the Industrial Revolution, which started around 1760 

Experts said diving around Shikine Island was ‘like a time machine’ and allowed them to check the impact of changing CO2 levels on marine life and coral reefs. By some estimates, oceans have become 30% more acidic since the Industrial Revolution, which started around 1760 

WHAT IS CORAL BLEACHING?

Corals have a symbiotic relationship with a tiny marine algae called ‘zooxanthellae’ that live inside and nourish them. 

When sea surface temperatures rise, corals expel the colourful algae. 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 recover if the temperature drops and the algae return, severely bleached corals die, and become covered by algae. 

In either case, this makes it hard to distinguish between healthy corals and dead corals from satellite images.

This bleaching recently killed up to 80 per cent of corals in some areas of the Great Barrier Reef.

Bleaching events of this nature are happening worldwide four times more frequently than they used to. 

An aerial view of Australia's Great Barrier Reef. The corals of the Great Barrier Reef have undergone two successive bleaching events, in 2016 and earlier this year, raising experts' concerns about the capacity for reefs to survive under global-warming

An aerial view of Australia’s Great Barrier Reef. The corals of the Great Barrier Reef have undergone two successive bleaching events, in 2016 and earlier this year, raising experts’ concerns about the capacity for reefs to survive under global-warming





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