When Bailey Thomasson first spotted the coral, she felt a jolt of relief. She was diving for samples off the Florida Keys, and the thicket of elkhorn coral below looked brown, not the stark white that would indicate bleaching from the record-breaking sea temperatures in the area. But as she swam closer, she realized the situation was far worse than she’d considered possible.
“The coral didn’t even have a chance to bleach, it just died,” said Ms. Thomasson, who works for the Coral Restoration Foundation, a nonprofit group based in the Keys. The brown color was not healthy coral but dead tissue sloughing off the skeleton, almost as if it had melted.