World could soon witness ‘historic’ coral die-offs

Severe coral bleaching has been reported across Northern Pacific

By Moushumi Sharma
Published: Monday 22 December 2014


The Northern Pacific region is witnessing massive coral bleaching due to warm sea temperatures and this could result in “historic” coral die-offs across the world in the near future. This has been observed by Mark Eakin, coordinator of the Coral Reef Watch programme of the US National Oceanic and Atmospheric Adminstration (NOAA).

Coral bleaching is a phenomenon where corals lose the symbiotic algae that give them their distinctive colour. Severe bleaching could lead to disease and partial mortality, and an entire colony of corals may die. Coral Reef Watch is a part of NOAA’s Coral Reef Conservation Programme. Its satellite data provides reef conditions to identify areas at risk for coral bleaching. 

Scientists warn that the current die-off could be the worst in two decades, according to The Guardian. A huge swathe of the Pacific has already been affected, including the Northern Marianas Islands, Guam, the Republic of the Marshall Islands, Hawaii, Kiribati and Florida. Some areas have recorded serious bleaching for the first time. Marshall Islands has witnessed bleaching of unprecedented severity—since September almost 100 per cent table corals have been killed by the rise in sea surface temperature. It is expected that rising temperatures will soon hit coral reefs in the southern Pacific and the Indian Ocean. Eakin predicts that Australia’s Great Barrier Reef could fall prey to coral bleaching as early as January 2015.

A repeat of 1998?
According to The Guardian report, the worst coral bleaching took place in 1998 when an El Niño event combined with climate change to raise global sea and air temperatures to never-before-recorded levels and killed around 15 per cent of the world’s corals. Year 2014 has already surpassed 1998 as the hottest year recorded (“2014 may turn out to be hottest year ever”. Could this mean another massive coral die-off? “Many coral reef scientists are expecting something similar to 1997-98 to unfold in the next six to 12 months,” Prof Ove Hoegh-Guldberg, a coral reef expert from the University of Queensland, told the newspaper.

Eakin says even under a weak El Niño, bleaching could continue until 2016, lasting twice as long as the 1998 event. “The real problem is that recovery from a major bleaching event can take decades and these events keep coming back every 10 years or less… (Reefs) just don’t have time to recover,” he adds.
Hoegh-Guldberg further says that the combined effect of rising temperatures and sea levels could mean the end for coral reefs in the next 50 years even if world leaders act to keep global temperature rise below the global target of 2 degrees Celsius.

Historical temperature variability affects coral response to heat stress

Elevated sea surface temperature during May 2010 induces mass bleaching of corals in the Andaman

Climate, carbon and coral reefs

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