The world's coral reefs face numerous threats, including climate change, pollution, and habitat loss. Since 2014, an aggressive disease has plagued the Florida Reef Tract—the world's third-largest barrier reef system, according to the National Oceanic and Atmospheric Administration (NOAA). The disease, called "stony coral tissue loss disease (SCTLD)," now impacts corals throughout the Florida Keys and the Caribbean. NOAA reports that SCTLD has infected and killed about half of the region's hard coral species.
According to NOAA, bacteria is likely the cause of stony coral tissue loss disease. The disease transmits easily through coral colonies by direct contact or water circulation. NOAA states that tissue loss appears as banding or blotching, and as it progresses, the diseased spots or bands can coalesce. While infections may persist in large colonies for several years, small colonies can die within a few weeks or months.
While scientists are concerned about the region in general, one coral species is of particular concern. Pillar coral is a rare Caribbean coral species that has been listed as threatened under the U.S. Endangered Species Act since 2014. The species experienced a 70% population decline in the region due to multiple bleaching events, white plague, and the unprecedented outbreak of SCTLD.
Scientists have identified 181 genotypes of pillar coral, and due to the combination of threats, only 51 genotypes remain. Of the remaining ecotypes, 40 are heavily diseased or have less than 5% of tissue remaining. NOAA reports that the species is considered reproductively extinct in this region and at high risk for extinction.
In an attempt to save this threatened species, in 2016, scientists collected pillar coral specimens to be cared for in nursery facilities. NOAA recently announced that this collaborative effort has mainly been successful in treating and rehabilitating diseased pillar corals. Scientists discovered that the corals respond well to antibiotic treatments delivered in a form similar to dental paste. The paste delivers the antibiotics directly to the coral tissue, stopping the disease progression in its tracks and healing damaged tissues.
Of the 208 specimens collected, 176 were treated successfully. Although it is not currently safe for them to return to the reefs, scientists are hopeful that they eventually will aid in restoring damaged reefs.