Third Time’s a Disaster: Latest Coral Bleaching Hits Reefs Worldwide

A 'warm blob' in the Pacific Ocean coupled with a strong El Niño could put more than 4,000 square miles of pristine coral reefs in harm’s way.

Airport Reef in American Samoa at the height of the bleaching event in February 2015. (Photo: XL Catlin Seaview Survey)

Oct 8, 2015· 2 MIN READ
Taylor Hill is an associate editor at TakePart covering environment and wildlife.

Scientists have confirmed that for only the third time ever recorded, bleaching is hitting coral reefs on a global scale.

The devastating impacts could be longer and more severe than any previous event, said researchers at the National Oceanic and Atmospheric Administration.

“The problem is, the water temperatures and coral bleaching we’re seeing now are what you would expect during an El Niño year, but we haven’t even gotten to the expected 2015–16 event yet,” said Mark Eakin, NOAA’s Coral Reef Watch coordinator.

What’s happened is that the giant, unusually warm water mass that has loitered in the Pacific Ocean since 2014 is about to merge with 2015’s expected El Niño weather event. Couple that with warmer ocean temperatures overall thanks to climate change, and as much as 4,633 square miles of vibrant coral reefs—approximately 38 percent of the world’s corals—could be damaged by the end of this year. Five percent of the reefs could be lost for good.

File fish are iconic reef fish that are totally reliant

on healthy corals for food. (Photo: XL Catlin Seaview Survey)

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Corals cover less than 1 percent of the ocean’s floor, but they’re vitally important to more than 25 percent of all marine life, acting as a home for thousands of species and food for others. For humans, coral reefs are a natural buffer against waves and storms, and nearly half of the fish species people eat rely on coral reef habitats at some stage of their lives. But with coral bleaching events seemingly on the rise, the entire ocean structure could be in danger.

Big coral bleaching episodes weren’t seen until the 1982–83 El Niño, and the first global bleaching event wasn’t recorded until the 1998 El Niño.

“Then we had one during 2010, a moderate El Niño, and now we’re having one just five years later,” Eakin said. “They seem to be occurring more frequently.”

In previous cases, the bleaching followed the warming ocean patterns associated with El Niño and La Niña events. Bleaching starts in the central and eastern Pacific during the fall and winter, and in the following spring and summer, bleaching occurs in the Indian Ocean and the “coral triangle” of Southeast Asia. The following year, Eakin said, bleaching can hit the Caribbean corals if the Pacific’s warming is powerful enough to influence temperatures elsewhere.

“What we’re seeing now is that the baseline ocean temperatures are higher when these El Niños are hitting, so corals are at a higher risk for bleaching even before these warm water seasons hit,” he said.

But as long as the world keeps emitting greenhouse gases like carbon dioxide into the atmosphere, ocean temperatures will continue to rise. A large percentage of carbon ends up in the ocean and increases acidification while rising temperatures warm the waters.

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The more acidic the water, the more susceptible corals are to bleaching at lower water temperatures. The hotter the water, the harder it is for corals to fight off disease.

“There’s a lot at play working against coral reefs right now,” Eakin said. “Back during the 1998 event, we were trying to make sense of the data, like watching a mystery unfold. But now, we have the satellite imagery and climate models to predict what water temperatures are going to look like in the future, and it’s like watching a train wreck in slow motion.”