Environment | Largest Ever Global Coral Bleaching Event Confirmed

Ocean scientists have confirmed a “global coral bleaching event” is currently underway.

By Amber Cobley

38% of the world’s coral reefs and over 12,000 square kilometres of reefs may be destroyed by the end of this year. And at huge costs; reefs support approximately 25% of all marine species and as a result, the livelihoods of 500 million people and income worth over $30 billion are at stake.

The event, only the third of its kind in history, is the first to be “officially declared”. Previous coral bleaching events were at the mercy of limited technology, understanding and man power to bring the catastrophic events into the limelight.

Thanks to XL Catlin Seaview Survey, times are changing. They believe insurers must take “a leading role in improving the understanding of potential changes to our environment”, and so set up its pioneering survey. With near-real-time satellite monitoring data from the US National Oceanic and Atmospheric  Administration (NOAA) and in partnership with University of Queensland, rapid response teams have, for the first time, captured devastating images of coral bleaching as it happened.

A before and after image of the bleaching in American Samoa. Left - December 2014, right -  February 2015 when the XL Catlin Seaview Survey responded to a NOAA coral bleaching alert - www.globalcoralbleaching.org

A before and after image of the bleaching in American Samoa. Left – December 2014, right – February 2015 when the XL Catlin Seaview Survey responded to a NOAA coral bleaching alert – http://www.globalcoralbleaching.org

Why this year?

Climate change is here to stay, but this year, effects have been strengthened by the intensification of a phenomenon known as “El Niño”. El Niño is the state of sea surface temperature in the equatorial Pacific Ocean, which has important consequences for weather around the globe. These warmer-than-usual water temperatures, combined with climate change, could potentially bring the strongest El Niño ever recorded. Although only lasting an average of 18 months, with forecasts remaining strong until early 2016, the worst may be yet to come!


NOAA: peak of the worst global bleaching event (1997/98) compared to the sea surface temperatures July 2015. It illustrates the strengthening 2015/16 El Niño which has triggered the 3rd global bleaching event – http://www.globalcoralbleaching.org

How does this affect corals?

Corals are actually thousands of tiny animals (“polyps”) that form a large colony inside a Calcium Carbonate skeleton. This skeleton, surprisingly, is entirely white! The coral’s vibrant colours actually come from the coloured algae (“zooxanthellae) that polyps house inside their body tissues. This is called “symbiosis”, because both animals benefit from this unique relationship; the algae release oxygen and nutrients that the coral polyp utilises and in turn, the polyp releases carbon dioxide to the algae.

However, under high temperature stress, the algae release compounds that are toxic to the coral and so they are expelled from the polyps.  This leaves the corals a striking white colour where their skeletons can be seen through the translucent coral tissue; “coral bleaching”. The corals inevitably die as they have lost their main food and respiratory source.

Our oceans have absorbed 93% of the heat from climate change and are now significantly warmer than they were 50 years ago. Coral reef bleaching is a startlingly sensitive, visual representation of our ruinous impact on our global oceans. One can only hope we take note before it is too late.