MIAMI — An underwater nursery project to restore the struggling coral reefs along Florida’s southern coast and the U.S. Virgin Islands will receive $3.3 million in national stimulus funding, according to an announcement Tuesday by the National Oceanic and Atmospheric Administration. The nonprofit Nature Conservancy will oversee the project, which expands four existing nurseries of staghorn and elkhorn coral and establishes two new nurseries. Over the next three years, about 12,000 corals will be grown to enhance coral populations at 34 degraded reefs from the Dry Tortugas - 70 miles west of Key West - to the waters off Broward County. The stimulus money pays for most of the salaries of 57 positions needed for the project. Staghorn and elkhorn, which have been designated national threatened species, have suffered from coral bleaching due to warming sea temperatures, diseases, hurricane damage and other threats. But in good conditions, these corals can produce numerous branches and grow four or more inches a year. ‘To conduct restoration of coral on this scale is unprecedented,’ said James Byrne, the Nature Conservancy’s marine science program manager for Florida and the Caribbean.