Study: Deadly Disease Affecting Coral Reefs in the Caribbean May be Transported in Ship Hulls

MIAMI, Florida – A new study suggests that ships may be spreading a deadly coral disease across Florida and the Caribbean.

Stony coral tissue loss disease (SCTLD) destroys the soft tissue of at least 22 species of reef-building corals, killing them within weeks or months of becoming infected. (via CMC)The findings by scientists at the University of Miami (UM) Rosenstiel School of Marine, Atmospheric, and Earth Science could help establish testing and treatment methods to mitigate the risk of further disease spread.

UM said on Tuesday that stony coral tissue loss disease (SCTLD) – which destroys the soft tissue of at least 22 species of reef-building corals, killing them within weeks or months of becoming infected – was first observed near Miami in 2014 and has since spread throughout all of Florida’s Coral Reef and into the Caribbean, including in waters off Jamaica, St. Maarten, US Virgin Islands and Belize.

Researchers suggest that transport through ship hulls, where the vessel takes on ballast water in one region to keep it stable and releases it at a different port, may have contributed to disease spread.

“Outbreaks in very distant locations suggest that disease transport was aided by means other than just ocean currents, such as through ship ballast water,” said the study’s lead author Michael Studivan, an assistant scientist at the UM Cooperative Institute for Marine and Atmospheric Studies (CIMAS) and NOAA’s Atlantic Oceanographic and Meteorological Laboratory.

The UM Rosenstiel School researchers said they conducted two disease transmission experiments in the Experimental Reef Lab at the Rosenstiel School of simulated ship’s ballast water and UV treatment of ballast water to determine whether SCTLD pathogens can be transported in this manner and whether established ballast water treatment approaches such as UV can successfully prevent the spread of disease.

UM said the first experiment exposed healthy corals to three types of water: disease-exposed; disease-exposed and UV-treated; and non-disease-exposed water in a flow-through tank system.

Over a six-week period, UM said the researchers observed the onset of disease lesions and mortality to determine the number of corals that became diseased, how quickly, and whether UV treatment of disease-exposed water resulted in fewer affected corals.

In a second experiment, UM said the researchers held the same types of water in containers to simulate a ship’s ballast tank for one and five days, then exposed the water to healthy corals to determine if the SCTLD pathogens could survive over time and whether they became more or less infectious over time.

UM said the researchers then tested the ballast water generated for both experiments in collaboration with the US Naval Research Laboratory in Key West, Florida, to quantify the microbial communities and their abundance in untreated and treated ballast water.

“The results suggest that ship’s ballast water poses a threat to continued spread and persistence of SCTLD throughout the Caribbean and potentially to reefs in the Pacific, and that established treatment and testing standards may not mitigate the risk of disease spread,” said Studivan.

The Experimental Reef Lab was designed and built by NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML) and CIMAS at the Rosenstiel School for conducting research on coral response to changing environmental conditions.

UM said the study, titled ‘Transmission of stony coral tissue loss disease (SCTLD) in simulated ballast water confirms the potential for ship-born spread’, was published on November 1, 2022, in the journal Scientific Reports.

The study’s authors include Michael Studivan, Michelle Baptist, Nash Soderberg, Ewelina Rubin from CIMAS; Ian Enochs from AOML; Vanessa Molina and Scott Riley from Excet, Inc., Matthew First from the US Naval Research Laboratory; and Ashley Rossin and Daniel M. Holstein from Louisiana State University.