Caring for "Reefugees"

The Building habitat in Surviving Through Adaptation at the National Aquarium is a bright window into the world of coral reefs. Unlike Blacktip Reef and Atlantic Coral Reef, which are filled with artificial coral, Building's corals are quite alive. These stony elkhorn, staghorn and mustard hill colonies stand out for another reason, too: these species are threatened throughout their home ranges in the Florida Keys, Gulf of Mexico and Caribbean. Thanks to a multi-agency effort, though, there's hope for them on the horizon.

Decades of Decline

Coral species throughout the Keys and Caribbean have experienced multiple stressors over time. Within the last half-century, they have had to cope with everything from increasing water temperatures to ocean acidification to disease—stressors that have led to episodes of coral bleaching and reduced colony growth. Then, in the last decade, a new threat emerged.

In 2014, coral colonies off the coast of Miami, Florida, began succumbing to a strange waterborne disease. Uneven white bands or blotches would appear along colonies' edges and expand, killing the living tissue and exposing the white, skeletal stone beneath. And it moved quickly, with half of all infected colonies often dying within months. It soon became apparent that this pathogen was unlike other infections.

Disease on coral reefs isn't unheard of. Outbreaks of white band disease had hit the elkhorn and staghorn populations in these areas starting in the 1970s. Though this new disease, dubbed stony coral tissue loss disease (SCTLD), didn't seem to strike elkhorn or staghorn, it easily infected many others. Since its first appearance, SCTLD has affected over 20 species and been spotted in reefs from Florida and the Yucatan peninsula to Curacao and Barbados.

A Refuge for Reef Builders

In response to this new threat, the Florida Department of Environmental Protection partnered with state and federal agencies and the Association of Zoos and Aquariums to rescue the affected species. They began collecting healthy corals from unaffected reefs and those that had survived in hard-hit areas, bringing colonies to the National Aquarium and other land-based facilities. In 2019, the Aquarium's Animal Care and Rescue Center became one of more than 30 sites across the U.S. holding healthy coral samples. The colonies at organizations like ours are kept safe from infection, cared for, and, in some cases, propagated to grow new colonies that could someday be planted on damaged reefs to help restore them. Meanwhile, scientists are looking for effective treatments for infected corals. They're also exploring some of the survivor colonies' genes to find sequences that could allow more corals to resist SCTLD in the future.

This rescue effort hasn't only helped the species affected by SCTLD. Colonies of critically endangered elkhorn and staghorn that had struggled to recover following repeated white band outbreaks were also included in the sampling. Since they aren't susceptible to SCTLD and are relatively fast-growing, they're great candidates to jumpstart reef restoration in the coming years. With luck, lots of hard work and breakthroughs in research, the future looks hopeful for these and many other coral species.