PICKLES REEF, FLORIDA — As soon as our boat reached the reef, the problem appeared. Looking downthrough the clear, turquoise water, I saw a handful of stark white patches on the seafloor, some 20 feet below.
I strapped on a tank, leapt into the ocean, and sank down near one of them. It was a large cluster of elkhorn coral, a threatened species that looks a bit like studded moose antlers sprouting from the reef. Normally, elkhorn is a vibrant, golden brown. Here it was bone white, a sunken skeleton.
