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Coral in a Warming World

This coral’s stark white color indicates that it is stressed, probably by warming water. Most corals host a type of algae that produce food for the live coral polyps and that also give reefs their vibrant color. As water temperature rises, corals often eject their algae, making the underlying white skeleton visible, and putting them at risk of starvation and death. This process is called coral bleaching, and it is increasingly common as global warming affects ocean temperatures worldwide. But it can also be mitigated by things such as ocean currents and the resilience of some coral species themselves. (Photo by Amy Apprill, Woods Hole Oceanographic Institution)