Far off the Texas coast there is a beautiful surprise in the Gulf of Mexico that draws divers from around the world: a stunning amount of coral coverage on undersea mountains. Sheltered in deep, cool habitat about 100 miles from shore, the coral reefs found in the Flower Garden Banks National Marine Sanctuary are among the healthiest in the world. But scientists say that like all reefs, they are fragile, and their location will only offer protection for so long in the face of a warming climate. The kind of devastating bleaching that has hit other reefs during the summer's record-breaking heat is among the top concerns of the federally protected area's acting supervisor.