Coral is a foundation species, one that creates the habitats that support biodiversity and provides essential shoreline protection. The waters of Dry Tortugas National Park are home to some 30 species of coral.  One type –- Elkhorn Coral -- rises above the rest, literally and figuratively, for its importance in the region. It also happens to be the most threatened.   A team from the U.S. Geological Survey looked into whether Elkhorn Coral grown in nursery conditions could be transplanted in Dry Tortugas National Park and other areas of the Florida Keys.