Researchers raise threatened staghorn and elkhorn corals at a nursery in the warm Caribbean waters off the southern coast of Puerto Rico. Known as a line nursery, workers affix small pieces of coral to rubber-coated wires suspended above the seafloor, a technique that has proved very successful.
Researchers start with staghorn coral fragments just 1.5 inches long (4 cm).
After about a year, once the corals are grown, they are transferred to sites where the corals have suffered damage in the past. Staghorn corals were "out-planted" to this site in 2008, and the species is now thriving at the reef.
This reef had healthy soft corals but no staghorn corals, a key reef-building species. Teams placed isolated staghorn colonies raised at the nursery at the reef about three years ago, and the species is now thriving.
In January 2012, teams undertook the largest "transplanting" project in the region to date, moving more than 1,200 staghorn corals from the nursery to sites in need of the species around the area. In this photo, newly-planted staghorns stand out on a reef that is lacking healthy, reef-building corals.