FORT LAUDERDALE, Fla. – Scientists with the Smithsonian’s National Museum of Natural History, with the assistance of Nova Southeastern University coral researchers, have discovered that a bacterial probiotic can slow the spread of stony coral tissue loss disease (SCTLD), an aggressive deadly infection affecting several species of reef-building corals in the Caribbean and the coast of Florida.
The findings, published today in the journal Frontiers in Marine Science, reveal that applying the probiotic treatment across already infected wild coral colonies on the Florida coast helped prevent tissue loss.
The new treatment provides a viable alternative to antibiotics, which only offers temporary protection and runs the risk of creating resistant strains of the coral disease.
“The goal of using the probiotics is to get the corals to take up this beneficial bacterium and incorporate it into their natural microbiome,” said Valerie Paul, the head scientist at the Smithsonian Marine Station in Fort Pierce, Fla., who co-led the new study. “The probiotics then will provide a more lasting protection.”
Stony coral tissue loss disease emerged in Florida in 2014 and has rapidly spread south throughout the Caribbean. Unlike other pathogens, which usually target specific species, SCTLD infects more than 30 different species of stony corals, including boulder-shaped brain corals and limb-like pillar corals. As it spreads, the disease causes the corals’ soft tissue to be discarded, leaving behind white patches of exposed skeleton. In a matter of weeks to months, the disease can devastate an entire coral colony.
NSU’s GIS & Spatial Ecology Laboratory led by Brian K. Walker, Ph.D., has been focused on combatting the coral disease since 2018, and his team has published numerous papers on the advantages of saving corals using antibiotic treatments.
“The goal of the probiotics is to enhance the corals microbiome in a way that allows them to resist the disease over longer periods of time,” he said. “These were the first experiments on corals in the field (on the reef) instead of in tanks. Our role was to select and map experimental reef sites/corals, take Smithsonian divers out to the sites, aid in conducting the experiments, and then periodically monitor the corals to evaluate treatment success.”
NSU’s monitoring efforts included collecting imagery for 3D coral models as well, with the Smithsonian researchers performing the data management, analysis, and most of the reporting.
Researchers have yet to identify the exact cause of SCTLD, but the pathogen appears to be linked to harmful bacteria. To date, the most common treatment for SCTLD is treating diseased corals with a paste that contains the antibiotic amoxicillin.
While the amoxicillin balm is very effective at stopping the spread of SCTLD, it needs to be reapplied to be most effective. This not only takes time and resources but also increases the likelihood that the microbes causing SCTLD could develop resistance to amoxicillin and related antibiotics.
“Antibiotics do not stop future outbreaks,” Paul said. “The disease can quickly come back, even on the same coral colonies that have been treated.”
While the probiotic appears to be an effective treatment for SCTLD among Florida’s northern reefs, more work is needed to calibrate the treatment for other regions. Paul contends that probiotics could become a crucial tool for combatting SCTLD across the Caribbean, especially as researchers continue to fine-tune how they are administered at scale to corals in the wild.
“Stony coral tissue loss disease is still ravaging the reefs after a decade and is currently killing thousands of corals in the Dry Tortugas, Florida’s coral diversity hotspot,” NSU’s Walker said. “The development and application of a probiotic that can effectively assist the coral’s natural defenses against this disease would preserve these critical habitats for future generations to enjoy.”
In addition to Paul, the new paper includes contributions from several coauthors affiliated with the Smithsonian Marine Station and the National Museum of Natural History, including co-lead author Kelly Pitts and Kathyrn Toth, both NSU alumni. Pitts and Toth conducted the field work for the project. The study also includes authors affiliated with the University of Maryland, University of North Carolina-Wilmington, and University of Florida.
The research was supported by funding from the Smithsonian and the Florida Department of Environmental Protection.
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Nova Southeastern University (NSU) is the largest private research university in Florida and a top employer in the state, with more than $5 billion in projected economic impact. NSU is classified as an R1 institution by the Carnegie Foundation among universities with the highest level of research activity. Visit www.nova.edu for more information.
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The National Museum of Natural History is connecting people everywhere with Earth’s unfolding story. It is one of the most visited natural history museums in the world. Opened in 1910, the museum is dedicated to maintaining and preserving the world’s most extensive collection of natural history specimens and human artifacts. For more information, visit the museum on its website, blog, Facebook, LinkedIn and Instagram.
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