Deadly coral disease sweeping Caribbean linked to water from ships

Researchers find ‘significant relationship’ between stony coral tissue loss disease and nearby shipping

A virulent and fast-moving coral disease that has swept through the Caribbean could be linked to waste or ballast water from ships, according to research.

The deadly infection, known as stony coral tissue loss disease (SCTLD), was first identified in Florida in 2014, and has since moved through 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 most deadly 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 reefs in one study had at least 10% of coral infected by SCTLD, and nearly a quarter had more than 30%. In Florida, regional declines in coral density approached 30% and live tissue loss was upward of 60%.

Biologist Emily Williams
Biologist Emily Williams moves corals between tanks as researchers try to find out more about an outbreak of SCTLD in Florida in 2019 Photograph: Lucas Jackson/Reuters

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

Judith Lang, scientific director at the Atlantic and Gulf Rapid Reef Assessment project, which has been tracking the disease, said: “The prevailing currents in the Caribbean push seawater to Florida and not in the reverse direction, and the predominant wind direction is westward. So human dispersal [to those three territories] in 2018 seems necessary.”

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

Research technician Danielle Lasseigne cuts a Pseudodiploria strigosa coral with a steel chisel
A research technician cuts a coral with a steel chisel to remove the section being killed by SCTLD, US Virgin Islands Photograph: Lucas Jackson/Reuters

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

Krista Sherman, senior scientist at the Perry Institute and a co-author of the recently published paper, said: “The disease is spread along about 75km of reef tract, about 46 miles – so for Grand Bahama that is a large structure of reef. We’re talking about mostly covering the entire southern coastline of the island.”

The disease is also widespread in the coral reefs of New Providence, where the Bahamas’ capital, Nassau, and main port are located. The study notes the presence of international container ships, cruise ships and pleasure boats at that location, as well as a fuel shipping station.

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

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

The locations where SCTLD is prevalent in the Bahamas are all popular with tourists, recreational fishers 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 Photograph: Lucas Jackson/Reuters

There are concerns that the coral disease could affect the country’s main fishery export, spiny lobster, said Adrian LaRoda, president of the Bahamas Commercial Fishers Alliance. Although the lobster fishers work further out to sea, the industry would be affected if the reefs die. The spiny lobster fishery brings in $90m (£66m) a year and employs 9,000 people.

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

The Bahamian government has set up a national taskforce to tackle the problem. Currently, the most effective treatment for the disease is the application of the antibiotic amoxicillin directly to the 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 tackle the possible human-made causes. “Given a chance, nature can heal naturally,” she said.

• The headline of this article was amended on 27 July 2021 to remove a specific reference to “wastewater”, and to better reflect the content of the article in terms of different types of water from ships being linked to stony coral tissue loss disease.

Jewel Fraser in Port-of-Spain, Trinidad

The GuardianTramp

Related Content

Article image
Nobel-winning stock market theory used to help save coral reefs
Portfolio selection rules on evaluating risk used to pick 50 reefs as ‘arks’ best able to survive climate crisis and revive coral elsewhere

Karen McVeigh

28, Nov, 2021 @3:00 PM

Article image
Sinking Maldives plans to reclaim land from the ocean
Vulnerable island nation split over project to dredge millions of tonnes of sand to create land for resorts and industry on Unesco reserve

Senay Boztas in Amsterdam

23, May, 2022 @6:30 AM

Article image
Click, clack and pop: sounds indicate health of coral reefs, study finds
Monitoring the planet’s ailing coral is costly and arduous. Now new research shows that scientists can do it by listening in

Sofia Quaglia

25, May, 2022 @3:35 PM

Article image
Scientists discover new coral species in Galapagos waters
Extensive survey of Galapagos reefs reveals several new species of life – and some that were thought to be extinct

Felicity Carus

09, Sep, 2009 @1:27 PM

Article image
A starfish is born: hope for key species hit by gruesome disease
US team succeeds in captive breeding of sunflower sea stars and aims to reintroduce them to the wild

Laura Paddison

15, May, 2021 @7:00 AM

Article image
Reef ball burials: the new trend for becoming ‘coral’ when you die
Do underwater cremation memorials help people regenerate marine habitats in death or are they a ‘greenwashing’ gimmick?

Abby Young-Powell

21, Feb, 2022 @7:45 AM

Article image
Highly contagious marine epidemic rips through Caribbean’s coral reefs
Frustration among scientists as many islands, hard hit by Covid and hurricanes, struggle to fight stony coral tissue loss disease

CJ Clouse

23, Apr, 2022 @9:00 AM

Article image
Back from the brink: the global effort to save coral from climate change
Underwater nurseries encouraging growth of coral fragments on fibreglass offer glimmer of hope for endangered ecosystems

Oliver Milman in Key Largo

26, Sep, 2018 @10:30 AM

Article image
Lotion in the ocean: is your sunscreen killing the sea?
Up to 14,000 tonnes ends up in coral reef areas each year, but scientists are divided on how we can best protect our skin without harming the environment

Emine Saner

06, Aug, 2021 @5:01 AM

Article image
One of UK’s rarest corals set to expand its range as climate change warms seas
Pink sea fan, at risk from bottom-trawling, predicted to spread northwards around coast up to Scotland as sea temperatures rise

Karen McVeigh

27, May, 2022 @11:00 AM