Warming oceans killing coral reefs

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Coral reefs around the world are experiencing a massive die-off that could be the worst in recorded history, a new study warns. Stoked by climate change and a powerful El Nino, record-high ocean temperatures have triggered the global event, which began last year and is expected to destroy 5 percent of the world’s coral reefs by 2016.

The temperature changes brought about a phenomenon known as bleaching, in which corals expel symbiotic algae that provide essential nutrients, causing the brilliantly colored reefs to turn ghostly white. A resilient reef can recover if water temperatures return to normal quickly, but if algae loss is prolonged, the coral eventually dies. Two similar global events took place in 1998 and 2010, but researchers predict the current one is likely to be more persistent— and deadly.

This year as many as 95 percent of all U.S. coral reefs are expected to see ocean temperatures that can lead to bleaching. Of those areas, 60 percent are likely to be “hit with severe thermal stress, and we’re going to see a lot of corals dying,” says Mark Eakin of the National Oceanic and Atmospheric Administration (NOAA). Oceanographers caution that the long-term consequences of coral bleaching could be severe. “One in every four species of fish lives on a coral reef,” says Ove Hoegh-Guldberg, of Australia’s University of Queensland. “Coral reefs provide food and livelihood to 500 million people.”