Chilling Photos Show Coral Bleaching Across the Globe

Corals are dying across the planet. The culprit? Ever-increasing temperatures are stressing out corals' colorful partners called zooxanthellae. The result? Bleached-white corals. Now, scientists with the National Oceanic and Atmospheric Administration (NOAA) have found the stressful conditions are expanding from Hawaii into the Caribbean. Because of the breadth and severity of the bleaching, NOAA scientists have declared a "global coral bleaching event," only the third such declaration on record. Here's a look at what's happening beneath the world's seas.

Before and after

This before-and-after image shows the corals in American Samoa, in the South Pacific Ocean, before (image taken in December 2014) and after the bleaching event (image taken in February 2015). Corals get their rainbow hues from the microscopic algae called zooxanthellae that live in their tissues and photosynthesize to produce food for the corals. In return, the algae have a snug place to live … that is unless conditions in the water become inhospitable and they die off. (Photo Credit: XL Catlin Seaview Survey)

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Bleached staghorn coral seen in this close-up image taken in February 2015 in American Samoa. Scientists think there are hundreds of species of the branching stony coral called staghorn; these reef builders take various colors and shapes "from flat platelike colonies to pillowlike clumps to the branching, antlerlike form," according to the Monterey Bay Aquarium. (Photo Credit: XL Catlin Seaview Survey)

The white skeleton of a coral that lost its colorful zooxanthellae during a bleaching event in American Samoa. Like other reef-building corals, this one is not a single organism but rather a colony of hundreds to hundreds of thousands of tiny animals called polyps. Each teensy polyp has a stomach that opens at one end (the mouth), which is encircled with tentacles. (Photo Credit: XL Catlin Seaview Survey)

As seen in early 2015, a reef in American Samoa turns drab during a bleaching event in which about 80 percent of this reef's corals died. Not all corals build reefs, but those that do start with free-swimming larvae. These little baby corals attached to a hard surface along the edges of islands or submerged rocks. As the colonial organism grows and expands, a reef is born. (Photo Credit: XL Catlin Seaview Survey)

Jeanna Bryner is managing editor of Scientific American. Previously she was editor in chief of Live Science and, prior to that, an editor at Scholastic's Science World magazine. Bryner has an English degree from Salisbury University, a master's degree in biogeochemistry and environmental sciences from the University of Maryland and a graduate science journalism degree from New York University. She has worked as a biologist in Florida, where she monitored wetlands and did field surveys for endangered species, including the gorgeous Florida Scrub Jay. She also received an ocean sciences journalism fellowship from the Woods Hole Oceanographic Institution. She is a firm believer that science is for everyone and that just about everything can be viewed through the lens of science.