A study shows that a virulent, fast-spreading disease in coral reefs that has ravaged the Caribbean may be linked to waste or ballast water from ships.
The deadly infection, known as rock coral tissue loss disease (SCLD), was first identified in Florida in 2014, and has since traveled through the area, causing great concern among scientists.
It spreads faster than most coral diseases and has an unusually high mortality rate It is among the species most susceptible to infection, making it the most deadly disease of all to affect coral reefs. More than 30 species of coral are susceptible. It was found in Jamaica in 2018, then in the Mexican Caribbean, Sint Maarten and the Bahamas, and has since been discovered in 18 other countries.
In Mexico, more than 40% of the corals in one study had at least 10% of the corals infected by SCTLD, and about a quarter had more than 30%. In Florida, regional decreases in coral density approached 30% and loss of living tissue increased by 60%.
Scientists are not yet able to determine whether the disease is caused by a virus, bacteria, chemical or some other infectious agent, but the peer-reviewed study in Frontiers in Marine Science supports the theory that ballast water from ships may be involved. It was performed in the Bahamas by scientists at the Berry Institute of Marine Sciences, and found that SCTLD was more prevalent in reefs that were closer to the main trading ports of the Bahamas, in Nassau and Grand Bahama, suggesting a possible link between the disease and ships.
“Prevailing currents in the Caribbean push seawater into Florida rather than in reverse, and the prevailing wind direction is west,” said Judith Lang, scientific director of the Atlantic and Gulf Reef Rapid Assessment Project, which tracks disease. [to those three territories] In 2018 it seems necessary.”
In 2017, the spread of deadly pathogens by ships discharging ballast water prompted the International Maritime Organization to implement the Ballast Water Management Convention, which requires ships to discharge ballast water — used to maintain ship stability — within 200 nautical miles from shore. In water at least 200 meters deep before entering the port, to ensure that it does not bring harmful foreign pathogens.
In the Bahamas, SCTLD has spread rapidly since it was first identified in December 2019.
“The disease is spread along 75 kilometers of reefs, about 46 miles — so for Grand Bahama, it’s a large reef structure,” said Christa Sherman, chief scientist at the Berry Institute and co-author of the recently published paper. the entire south of the island.”
The disease is also rampant in the coral reefs of New Providence, where the capital of the Bahamas, Nassau, and the main port are located. The study indicates the presence of international container ships, cruise ships and pleasure boats at that location, as well as a fuel charging station.
Infection rates among the most sensitive species were 23% and 45% across New Providence and Grand Bahama, respectively, and recent mortality rates reached nearly 43%.
With the exception of two species, the researchers found that there was a “significant relationship” between the disease and the reef’s proximity to major shipping ports. They noted, “the proportion of healthy colonies increased with increasing distance from the port on both islands, and a greater proportion of recently dead colonies closer to the port than farther away.”
Sherman said the sites where SCTLD is common in the Bahamas are all popular with tourists, recreational fishermen and divers.
Adrian Larroda, president of the Bahamas Alliance of Commercial Fishermen, said there are concerns that coral disease could affect the country’s main fish export, spiny lobster. Although lobster fishermen work more at sea, the industry will be affected if the reefs die. Fishing spiny lobsters make $90m (£66m) a year and employ 9,000 people.
“Any negative impact on the corals will definitely affect the spiny lobsters significantly as the mature animals migrate.” [from the reefs] For fish collecting equipment [a technique for catching fish]LaRuda said. He added that the reproduction rate of lobsters and the food supply of baby lobsters in the reef will also be affected.
The Government of the Bahamas has established a National Task Force to address the problem. Currently, the most effective treatment for this disease is the application of the antibiotic amoxicillin directly to corals, which has seen some success in reducing mortality, but no realistic permanent solution is available.
According to Lang, rather than treating the symptoms, there is a need to address potential man-made causes. “If given the opportunity,” she said, “nature can heal naturally.”