Widespread coral bleaching threatens world’s reefs

fire coral

BEFORE AND AFTER  Healthy coral are full of color, like the fire coral seen on the left. But stressors, including overly warm ocean water, cause symbiotic algae to abandon coral tissues, bleaching them (right).  

XL Catlin Seaview Survey

Corals across the globe are experiencing widespread bleaching from high ocean temperatures, the National Oceanic and Atmospheric Administration states in its latest Coral Watch Report. Stressful conditions in the Pacific and Caribbean could last into early 2016. This is the third such global bleaching event in 17 years, NOAA notes.

Bleaching happens when corals get stressed. Overly warm water causes them to expel the symbiotic algae that give coral their color and are the corals’ major food source.

By the end of this year, NOAA predicts that nearly all U.S. coral reefs will have been subject to stressful bleaching conditions. The agency says global warming and this year’s strong El Niño are mostly to blame.

While corals can recover from mild bleaching, severe or long-term bleaching will kill them. If they do pull through, corals can be more susceptible to disease. Without corals, reefs — and the protections they provide other species and as storm barriers — disappear.

Before and after images on Google Street View show bleaching damage of a reef in American Samoa between 2014 and 2015. Google/XL Catlin Seaview Survey

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