The last, largest stands of ancient elkhorn coral survive in shallow waters off North Key Largo, where rough seas sometimes expose thick golden branches reaching toward the sunlit surface.Forty years ago, elkhorn grew in dense forests that would cover parking lots. Now, the biggest clump would barely fill one space.In another 40 years, elkhorn could disappear altogether -- along with just about every other hard coral forming South Florida's once-vibrant barrier reefs.Federal regulators last week designated a 1,329-square-mile strip of sea bottom stretching from southern Palm Beach County to the
