El Niño, Global Warming Exacerbate Coral Die-Off

Fire coral before and after bleaching. (Credit: XL Catlin Seaview Survey)

According to a release from the American Geophysical Union, an unusually strong El Niño combined with a continued rise in ocean temperatures due to global warming has led to a third mass coral bleaching and die-off which began in 2014 and may last until 2017, researchers warn.

The coincidence of weather phenomena is expected to put additional stress on corals around the globe, with many reefs already suffering from previous bleaching events, continuing ocean acidification and a higher likelihood of disease and stress.

Satellite images from 2014 and 2015 show a direct relationship between global areas of high thermal stress and areas with catastrophic coral bleaching. Similar global bleaching events also occurred in 1998 and 2010. The bleaching events turned out to be especially bad, the study showed, because they occurred close enough together to prevent coral recovery from previous bleaching.

Coral reefs in the Fiji Islands, for example, are experiencing large coral casualties because of bleaching events two years in a row. Southeast Asian corals have been among the hardest hit, having been struck by the 1998, 2010 and now 2015 events, causing even faster-growing corals to have difficulty recovering.

Top image: Fire coral before and after bleaching. (Credit: XL Catlin Seaview Survey)