Coral disease and invasive algae accelerate loss of reefs in Mexico

For more than a decade, the scientific community has feared that coral reefs around the world will “cook” if the sea temperature rises more than 2º Celsius as a result of global warming, which, they warn, affects ocean acidification and coral bleaching.

The Intergovernmental Panel on Climate Change (IPCC), a UN scientific body, has a less conservative prediction that coral reefs will not resist temperature rises over 1.5ºC by 2050, since a huge quantity of climate-altering greenhouse gas emissions continues to be released into the atmosphere.

To this adverse scenario add other factors that accelerate the degradation of coral ecosystems, such as pollution of the sea due to unsustainable urbanization, tourism, fishing, agricultural and industrial practices. All of these phenomena threaten to extinguish species that build reefs, such as pillar and labyrinth coral.

Scientists, authorities and civil organizations consulted by El Universal warn about the future of the Mesoamerican Reef (MAR), which extends 1,500 kilometers from Quintana Roo, Mexico, through Belize and Guatemala to southern Honduras, making it the largest coral reef in the Atlantic. They’ve identified two emerging phenomena that could cause its possible collapse within the next two decades, even before ocean temperatures reaching a “boiling” point.

One is Coral Tissue Loss Disease (SCTLD), hereinafter referred to as white syndrome, as it is named in Spanish. This disease kills corals’ living tissue and could become the most lethal coral disease ever recorded, with serious consequences for the physical functionality of the reefs in the Caribbean.

The other is the proliferation of sargassum, a pelagic macroalgae whose massive arrival, accumulation and decomposition on the coasts change the optimal conditions of seawater needed for the health of corals, marine animals like polyps and a skeleton of calcium carbonate, which maintains a close relationship with a species of algae called zooxanthellae.

Corals build reefs

Different species of coral grow at different speeds, the fastest being Acropora palmata, which grow six to 10 centimeters per year. Other species grow less than one centimeter annually, according to Lorenzo Álvarez Filip, president of the Mexican Society of Coral Reefs. On average, it takes more than a century for coral to reach sizes big enough to provide environmental services, such as fisheries production, which gives jobs and food to riverside and urban communities; tourist attractions and scenic beauty, which can benefit local economies; and protection, since coral reef acts as a natural barrier against hurricanes and storms in a region prone to such events.

The reefs of the Mexican Caribbean alone contribute US$9.5 billion annually to the economy and are the cradle of a very high biological diversity, according to the White Syndrome Action Plan prepared in 2019 by Mexico’s National Commission of Natural Protected Areas (Conanp, by its acronym in Spanish), businessmen, academia and civil society.

Quintana Roo is currently the section of the Mesoamerican Reef most affected by white syndrome, a disease originally detected in 2014 and baptized in Florida.

It can kill corals in just over a month. There is currently no treatment.

In 2018 it arrived in the Mexican Caribbean and spread rapidly to Belize, Jamaica and the islands of the Greater Antilles. In Honduras there are already outbreaks.

With the exception of the Reserve of Banco Chinchorro, the disease already covers sections of the MAR in Quintana Roo, where the death of species such as the Pillar Coral and the Labyrinth Coral has accelerated, according to the Laboratory of Reef Biodiversity and Conservation (Barco Lab) at the Autonomous University of Mexico (UNAM, by its acronym in Spanish) and the Conanp regional office.

“You are talking about losses of more than 90%; the species is practically disappearing from our coasts,” warned Álvarez Filip. “And if this happens, maybe we will start talking about certain species that are in danger of extinction. If it is only in Mexico, it would be local, but if it is in the entire range of distribution, we could talk about the extinction of the species.”

White syndrome’s origins unknown

White syndrome accelerates the loss of the living tissue of the coral, undressing its calcium carbonate skeleton and leaving a white strip where the lesion progresses. This process leaves it defenseless to the recolonization of other organisms, especially algae.

Without living tissue, the coral becomes a stone that will be eroded naturally over time until it becomes flat or disappears, a process that will not happen overnight, but will occur eventually, Álvarez Filip said. 

The surprising onslaught of the disease - preceded by other threats decades ago – took off guard several sectors and the general population in the region, leaving them without adequate regulatory frameworks, financial resources and technical capacity to contain and remedy their consequences, admits Cristopher González Vaca, who served as regional coordinator of Conanp until last November 2019

“It is definitely something that is unprecedented; there was no record of this disease or infection,” in Mexico he said. “It is an emerging phenomenon that arises almost suddenly; although we had the history of [what happened in] Florida, its speed in the Mexican Caribbean caught us all” off guard.

The scientific community does not know if the pathogen causing the disease is a bacterium, fungus or virus. They do not have a specific treatment. They have tried with a mix of antibiotics and natural ingredients, but none have worked.

There are more questions than answers, said Dr. Eric Jordán Dahlgren, a researcher from the Institute of Marine Sciences and Limnology (ICMyL, by Spanish acronym) at UNAM in the south of Cancun. The most accepted, although inconclusive explanation, is that it is a set of bacteria that coupled with environmental degradation increase stress on the corals and weaken their defenses.  

“Since the 80’s, 90’s we have lethal, very powerful epidemics that have been affecting the corals that build the reef,” said Dr. Jordan.

“It takes us totally off guard, without enough knowledge. And even if we knew, what do we do? Here at sea, assuming we knew what it is and how to fight it, would you go to each coral? How do you isolate them? It would be extraordinarily expensive and probably impractical,” he explained.

Between 1980 and 1990, Dr. Jordan documented that other diseases, such as white band, killed 80% to 90% of Horn of Elk (Acropora palmata) and Horn of Servant (Acropora cervicornis) corals in the Mexican Caribbean. In 2010 both received special protection within the Official Mexican Standard (NOM-059-Semarnat-2010).

In 1985, in Puerto Morelos, Akumal and Mahahual, Star Coral  (Orbicella annularis) covered more than 60 percent of the area’s reef. But by 2005 its coverage barely reached 10 percent, according to Dr. Jordan’s records. Together with the Acroporas, Pillar Coral (Dendrogyra cylindricus) are the main reef generators.

"In 20 years, we lost 50% of coral reef-building corals due to diseases that were not white syndrome," recalls Dr. Jordan.

Coral cemeteries

White syndrome infected more than 20 of the 45 existing coral species in Quintana Roo from June to December 2018, killing 30 percent of the affected species, according to Álvarez Filip, who documented the recent deaths of these corals and compared it with the information he and Dr. Jordan have collected since 1980. 

According to their research, the losses caused by white syndrome are equivalent to the number of coral species that the state lost in the last 40 years.

Álvarez Filip, who also works as a researcher at the ICMyL Reef Systems Academic Unit, presented data on Dec. 4, 2019, to the Advisory Council of the Puerto Morelos Reef National Park, a natural protected area affected by the white syndrome.

Minutes before his presentation, in a conversation with El Universal, the researcher referred to the Quintana Roo sea as a “coral cemetery.”

“The story is not encouraging. The effects of white syndrome have been devastating,” said Álvarez Filip, pointing to the example of the pillar coral (Dendrogyra cilyndrus), which, he said, “forms structures similar to underwater cathedrals” and can measure from five to six meters high.

“Basically, in the last six months we have dedicated ourselves to finding corpses of this coral. On December 3 we went to Tulum to attend the report of a [live] Dendrogyra; in Cozumel they have been able to keep a colony alive. But the sad reality is that 99% of corals of this species have died throughout the Mexican Caribbean, with the exception of Banco Chinchorro,” he emphasized

Another species in this condition is the labyrinth coral (Meandrina meandrites); 98% percent of its colonies have been lost in Quintana Roo.

“It's really shocking to see these mortalities so high,” Álvarez Filip continued. “As an example, imagine that you are in a football stadium with 100,000 people and, suddenly, 99,999 people are dying and there is still one person living ... This is the magnitude of what we are seeing with these coral species.”

As of last July, researchers from UNAM Biodiversity and Reef Conservation Laboratory focused on detecting and evaluating diseased coral colonies on reefs in Puerto Morelos, Cozumel and Tulum. Now they count dead colonies.

“What we find are cemeteries, lots of dead corals. We no longer see the disease, because many of the corals that got sick, died. Basically, we are telling what we have left. The colonies that were going to die, have already died,” said Álvarez Filip.

Economic impact

The tourism industry along the coast of Quinta Roo state - officially comprising 107,000 hotel rooms, bars and restaurants that depend largely on the presence of healthy beaches and pristine waters - will be the most affected economically if the coral reef continues to decline.

Even the fine white sand that draws visitors there comes from the natural decalcification of the coral and from the parrot fish that live in the reef, eat the coral’s skeleton and, after a digestive process, defecate grains of sand that form the beach.

According to a study prepared by Conanp, it will cost 5,493 million pesos (US$304 million) to keep the “Cozumeleño” reef in its best condition for the 1.8 million tourists visiting the island.

The economic value of Cozumel’s reefs, in terms of protection against extreme weather events, is 596 million pesos (US$32.8 million) annually.

Rodrigo Navarro Benítez, a member of the Advisory Council of “Arrecifes de Cozumel National Park,” indicates that it is the reef that attracts vacationers to the island. If coral degradation continues, according to Conanp’s study, 12 percent of tourists would stop visiting, causing an annual loss for the local economy of 1,500 million pesos (US$83).

In October 2019, the Advisory Council - made up of authorities, businessmen, civil and academic organizations - decided to partially close, to December 15^th, 11 of more than 20 sites, within the National Park, to give rest to the corals, reduce their stress and help strengthen their defenses against white syndrome, Rodrigo Navarro, director of the Jean-Jean Michael Costeaus’ Ocean Futures Society recalls.

Despite this measure, the disease did not collapse, so the Councli has provided for the closure of the entire protected area, once a year, said Navarro.

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* Translation by Alejandra Serrano Pavón

A Spanish-language version of this story first appeared in El Universal on 23 Dec. 2019. It was produced with the support of the Earth Journalism Network's Mesoamerican Reef Reporting Project.

Banner image: White syndrome found on a section of corals in Fish Market, Puerto Morelos, on July 3, 2018 / Credit: Lorenzo Álvarez Filip