Coral bleaching in the Fl. Keys National Marine Sanctuary, Oct. 2015

Two colonies of the mustard hill coral, Porites astreoides, one apparently healthy (left) and one visibly bleached (right) during a coral-bleaching event at Hen and Chickens Sanctuary Preservation Area, Plantation Key, FL, USA. When ocean temperatures were unusually warm in the Florida Keys National Marine Sanctuary in October 2015, coral bleaching resulted from the high-temperature stress. Some corals appeared to resist the stress better than others of the same species, giving hope that there is genetic diversity upon which natural selection can act. Coral restoration efforts could help coral populations persist under continued climate change by maximizing the diversity of corals used for propagation.