White syndrome: rare disease threatens the Mexican Caribbean corals
In a little more than a year, these reefs have lost more than 30% of their coral cover due to this disease dubbed the "white syndrome," which converts these colorful organisms into inert calcium carbonate skeletons.
Experts warn that the plague could kill much of the reef, a magnificent arch of more than 1,000 kilometers of coral shared by Mexico, Belize, Guatemala and Honduras, the largest in the world after Australia's Great Barrier Reef.
Its disappearance would also devastate the vital tourism industry around it, although tourism is likely to be at the root of the problem.
The white syndrome was first detected in July 2018 in the Arrecifes National Park of Puerto Morelos, in the northern Mexican Caribbean, when scientists discovered that the corals were getting sick and dying quickly.
Sharing their findings with the international community, they confirmed their fears: it was the same "lethal" disease detected off the coast of Florida since 2014, explains Melina Soto, a representative in Mexico for Healthy Reefs for Healthy People.
In 15 months, the plague has advanced more than 400 kilometers south of the Mesoamerican reef to Belize. Within weeks, this pathogen can destroy the living tissue of coral colonies that took decades to form, warns Soto.
"If we continue at this rate, we can predict that this ecosystem will be collapsing in the next five or 10 years".
According to scientists, the white syndrome is more dangerous than coral bleaching, another disease that has affected several of the planet's reefs, such as the Australian reef.
The bleaching of corals - which are colonies of tiny animals - is caused by the loss of the microalgae known as zooxanthellae that live inside them and give them their brilliant colour.
Caused by any environmental stress, such as rising temperatures, coral bleaching can be overcome if the environment recovers.
White syndrome is lethal
"It is a detachment of coral tissue that dies and when it detaches leaves exposed the skeleton, which is white," said Claudia Padilla, of the Regional Fisheries Research Center (Crip) in Puerto Morelos. To an inexperienced eye, the impact of the syndrome is still not as visible.
"I had never seen corals and they seemed wonderful to me, I would never have thought they were dying," said Emanuel Fernández, a 34-year-old Argentine chemical engineer after a snorkeling trip to Isla Mujeres, in the Mexican Caribbean. Experts, on the other hand, do notice the damage.
"Before, you used to go, dive and see the colonies on the reefs you frequented, now we go and all those colonies are dead." According to Padilla, 25 of the 40 species of corals on the Mesoamerican reef have been affected by this disease, and three are at imminent risk of extinction. They are even working on a project to genetically safeguard coral species endangered by this plague, with a view to restoring the reef in the future.
Impact of tourism
Researchers march against the clock to understand the causes of the white syndrome. One likely cause is poor water quality caused by a variety of factors, such as the dumping of sewage, the decomposition of twill, an algae whose presence has increased greatly in recent years, another environmental emergency for the region, or even the disproportionate use of sunscreens, sunscreens and repellents with which people enter the water, banned a couple of months after it was confirmed that it affects the reproduction of corals.
"A particle of the blockers, oxybenzone, affects and impedes coral reproduction," warns Christopher González, regional director of the National Commission of Protected Natural Areas.
This month, authorities temporarily closed the "Palancar", "Colombia" and "El Cielo" reefs, which annually receive thousands of visitors arriving on cruise ships to the island of Cozumel.
Authorities, the tourism industry, and the population must now seek a delicate balance: a level of tourism that does not kill the reef or the economy. So far in 2019, the reefs of the Mexican Caribbean have been visited by some 725,000 tourists, a figure similar to previous years.
"If we lose the reef, we lose our main economic activity, which is tourism," warned María del Carmen García, director of the Arrecifes de Puerto Morelos National Park.