Friday, January 21

Deadly Caribbean Coral Disease Linked to Ship Sewage | Coral

A virulent, fast-moving coral disease that has spread across the Caribbean could be linked to debris or ballast water from ships, research shows.

The deadly infection, known as stony coral tissue loss disease (SCTLD), was first identified in Florida in 2014 and has since moved across the region, causing great concern among scientists.

It spreads faster than most coral diseases and has an unusually high mortality rate. among the species most susceptible to it, making it potentially the deadliest disease ever to affect corals. 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 detected in 18 other countries.

In Mexico, more than 40% of the reefs in a study had at least 10% of the corals infected with SCTLD, and nearly a quarter had more than 30%. In Florida, regional declines in coral density approached 30% and the loss of living tissue was greater than 60%.

Biologist Emily Williams
Biologist Emily Williams moves corals between tanks as researchers try to find out more about an SCTLD outbreak in Florida in 2019

Scientists have not yet been able to determine whether the disease is caused by a virus, bacteria, chemical, or some other infectious agent, but peer review study in Frontiers in Marine Science journal supports the theory that ballast water from ships may be involved. Conducted in the Bahamas by scientists from the Perry Institute of Marine Sciences, it found that SCTLD was most prevalent on reefs that were closer to the main commercial ports of the Bahamas, in Nassau and Grand Bahama, suggesting a possible link between the sickness and ships.

Judith Lang, scientific director of the Atlantic and Gulf Rapid Reef Assessment project, which has been tracking the disease, said: “The prevailing currents in the Caribbean push seawater toward Florida rather than the other way, and the prevailing wind direction is westward. So human dispersion [to those three territories] in 2018 it seems necessary “.

In 2017, the spread of deadly pathogens by ships when they discharge ballast water led the International Maritime Organization to implement the Ballast Water Management Convention, which requires ships to discharge their ballast water, used to maintain the stability of the ballast water. ship, 200 nautical miles offshore in water at least 200 meters deep before entering the port, to ensure that they do not bring harmful foreign pathogens.

Research Technician Danielle Lasseigne cuts a coral Pseudodiploria strigosa with a steel chisel
A research technician cuts a coral with a steel chisel to remove the section that is killing SCTLD, US Virgin Islands.

In the Bahamas, SCTLD has spread rapidly since it was first identified in December 2019.

Krista Sherman, senior scientist at the Perry Institute and co-author of the recently published paper, said: “The disease spreads over about 75 km of reef length, about 46 miles, so Grand Bahama is a large structure. reef. We are talking about covering mainly the entire southern coast of the island.

The disease is also widespread on 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 container ships, cruise ships and international pleasure boats in that place, as well as a fuel dispatch station.

Infection rates among the most susceptible species were 23% and 45% in New Providence and Grand Bahama, respectively, and recent mortality rates have reached nearly 43%.

With the exception of two species, the researchers found that “there was a significant relationship” between the disease and the proximity of the reefs to the main shipping ports. They noted “an increasing proportion of healthy colonies as the distance from the port increased on both islands, and a greater proportion of recently killed colonies closer to the port than further afield.”

The places where SCTLD is prevalent in the Bahamas are all popular with tourists, recreational fishermen and divers, Sherman said.

Kevin Macaulay applies an antibiotic ointment to an Orbicella faveolata (Mountainous Star Coral)
A research assistant applies an antibiotic ointment to a mountainous star coral affected by SCTLD near Key West, Florida.

There is concern that the coral disease could affect the country’s main fishery export, the spiny lobster, said Adrian LaRoda, president of the Commercial Fishermen Alliance of the Bahamas. Although lobster fishers work more offshore, the industry would suffer if the reefs die. The lobster fishery brings at $ 90 million (£ 66 million) a year and employs 9,000 people.

“Any negative impact on our reefs would definitely drastically affect our lobsters because mature animals migrate [from the reefs] to fish aggregation devices [a technique for catching fish]LaRoda said. He added that the lobster reproduction rate and the food supply for juvenile lobsters on the reef would also be affected.

The government of the Bahamas has created a national task force to address the problem. Currently, the most effective treatment for the disease is applying the antibiotic amoxicillin directly to corals, which has had some success in reducing mortality, but no realistic permanent solution is available.

Instead of treating symptoms, Lang says, you need to address potential human causes. “If given the opportunity, nature can heal itself naturally,” he said.

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