A rapidly spreading coral disease detected in the Caribbean waters has been linked to ballast water dumped by passing ships. It was first detected in the reef tracts off the coast of Florida back in 2014 and has now spread alarmingly in the Caribbean. Scientists suspect that the infection is being caused by the release of untreated ballast water close to the shore by passing ships.
The coral disease has been called the stony coral tissue loss disease (SCTLD). It is perhaps the deadliest of the coral diseases to strike the region given the rapidity with which it has spread. The high rate of mortality rate has decimated over 30 coral species.
While ballast water is necessary for the stability of the ships, but its discharge can also introduce harmful microalgae and other organisms into the environment. They also transport invasive species that create environmental problems throughout the oceans of the world.
It was first detected in the Caribbean in 2018 in Jamaica, then spread to the Mexican part of the Caribbean, the Bahamas, and Sint Maarten. The coral disease has since spread to 18 countries.
A study in Mexico revealed that over 40% of the coral reefs studied showed an SCTLD infection rate of 10%. More than a 30% rate of infection was detected in over a quarter.
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In the regions around Florida, the regional fall in coral density due to coral disease was close to 30%. The loss of live tissue was found to be more than 60%.
Scientists are yet to pin down all the causes of this coral disease. They haven’t been capable of determining if it has been caused by a bacterium, chemicals, or virus from infectious agents. But the researchers are unanimous that the discharge of ballast water by passing ships is one of the causes. Scientists from the Perry Institute for Marine.
Coral Disease Linked To Shipping Activity
Scientists who have conducted their research in the Bahamas have found that the disease was widely predominant in reefs close to the major ports in the Bahamas, in Grand Bahama and Nassau. This clearly points to a link between shipping activity and coral disease.
Scientific director Judith Lang of the Atlantic and Gulf Rapid Reef Assessment project says that tides originating from the Caribbean region push the seawater towards Florida. The wind direction is also predominantly westwards. So it becomes natural that dispersal is directed towards these 3 territories.
The Ballast Water Management Convention was put in place by the International Maritime Organization to counter the spread of deadly pathogens due to the discharge of polluted ballast water by passing ships.
This convention requires ships to release the ballast water, which maintains the stability of the ship, at a distance of 200 nautical miles (230 miles) from the shore at a depth of 200 meters before they enter a port. This ensures that no toxic pathogens are discharged close to the shores.
The Bahamas has seen a rapid spread of the coral disease since it was first detected around December 2019. Co-author of the study, Krista Sherman, who is a senior scientist at the Perry Institute, says that the disease has spread along 46 miles (around 75 kilometers) of the reef tract. That comprises a large tract of the Grand Bahama. The spread of the coral disease is along almost the island’s entire coastline.
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The coral disease has also been detected in the New Providence coral reefs close to Nassau, the capital of the Bahamas, and the location of its main port. Mortality has reached close to 43% recently.
Researchers found a link between the presence of healthy coral reefs and the distance from major shipping activity. The regions most affected by SCTLD are popular tourist destinations where diving and recreational activities take place.
The Bahamian administration has deployed a task force to deal with the pressing problem. The direct application of amoxicillin has proved to be most effective against the disease. But though this has helped to curb mortality to some extent, it is not seen as a permanent solution to the problem. Lang says that the causes need to be tackled instead of treating the corals. Once the cause of the coral disease is stopped, the coral will heal naturally.