A decade after the first sargassum blooms were spotted in the South Atlantic, these massive brown mats of macro-algae represent one of the largest ecological threats to the Caribbean, a mega-diverse region whose tens of millions of inhabitants heavily depend on tourism and natural resources.
Now 2021 looks like it will be particularly bad, scientists predict. The floating sargassum bloom has shown accelerated growth since December, according to satellite monitoring reports carried out by the University of South Florida and NASA.
“The crisis is coming again for the Caribbean coasts,” warns Alejandro Bravo Quesada, specialist in marine oceanography and the director of Ocean Solutions Mexico. Meanwhile, the suspected causes of this sargassum surge – including deforestation and increased fertilizer use in the Amazon region, along with climate change – are continuing unabated.
The latest reports show the amount of sargassum in the sea went from 3.2 million tons in December to 4.6 million tons in February – four times more than reported in February 2020. The monitoring reports indicate this is comparable to the record amounts seen in 2018 and 2019, when the brown sargassum tide transformed the Caribbean coasts of turquoise waters and white sands.
The accumulation of sargassum in the Atlantic Ocean over the past five years is shown in a graphic from the Optical Oceanography Laboratory at the University of South Florida.
“The sargassum phenomenon has begun to show some behavior patterns since we started to observe it more carefully, in 2015,” said Bravo Quezada, who advises the Mexican state government of Quintana Roo about this phenomenon. “The blooming season begins early in the year and has its highest peaks in the summer, showing a significant decline in the winter. We see that it has annual periods of greater intensity, then less and then it rises again. These patterns indicate that most likely this year we will have large quantities.”
At 33 square miles, the sargassum belt as of February was south of the Lesser Antilles, which had already experienced minor landfalls. The dynamics of the maritime currents and the trajectory that the floating mats have followed in previous years allow experts to infer that the sargassum is likely to travel westward through the Caribbean region until it meets the Mexican coasts, where it circles back and heads to south Florida.
For the past six years, tourists have been greeted at Caribbean destinations by images of brown water, a foul odor, dead marine fauna and tons of accumulated algae on the coast, especially during peak periods of sargassum landfall.
Massive brown mats of sargassum macro-algae represent one of the largest ecological threats in the Caribbean Sea, a mega-diverse region whose tens of millions of inhabitants heavily depend on tourism and natural resources. (Photo from InfoAmazonia)
The bad sights and smells are only the beginning of a regional “environmental disaster” if it is not managed soon, warns Rosa Elisa Rodríguez, a researcher at the National Autonomous University of Mexico’s Institute of Limnology and Marine Sciences.
The sargassum piling up on the coasts already affects seagrass meadows, mangroves, reefs and beaches, and threatens the economy of regions that essentially live on tourism, including Quintana Roo in Mexico, the Dominican Republic, Jamaica, Belize and Aruba, among others.
Although there is currently no consensus figure on the economic effect of the sargassum in the Caribbean, Edmund Bartlett, co-chair of the Global Tourism Resilience and Crisis Management Center, said in 2019 that governments spent about $120 million trying to clean Caribbean beaches, with limited success.
This estimate does not include the amount that each hotel allocates to clean up its own beachfront every day, which hotel owners estimate can total $60,000 annually for a medium-size hotel. The estimates varies widely, depending on the beach size, location and the quantity of sargassum to be removed.
Sargassum is removed from a beach.
In addition to cleaning costs, some hotels might be losing money because of a decline in tourist arrivals. For example, between 2018 and 2019, Cancun had a drop in hotel occupancy that in some cases reached 15 percent, says Abelardo Vara Rivera, honorary president of the Cancun, Puerto Morelos and Isla Mujeres Hotel Association.
Over the past year, the hotel industry has suffered an additional crisis due to the COVID-19 pandemic. That means the sargassum problem is not in the spotlight, but if the ecological threat is not addressed, it could worsen, warns Vara Rivera.
The environmental and economic effects have led to a desperate search for solutions from the scientists and governments in many countries, but have yet to lead to effective actions.
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In June 2019, the first international convention to address the sargassum problem was held in Cancun, Mexico. Representatives from 13 Caribbean countries agreed to work together to address the phenomenon. The commitment was endorsed in a second meeting four months later on the island of Guadalupe.
Nevertheless, it is a complex problem to address, starting with its origin, says biologist Adán Caballero Vázquez of the Yucatan Center for Scientific Research, who has studied the invasion of this macro-algae and its associated fauna for many years. Caballero Vázquez says the sargassum that reaches the Caribbean does not come from the famous Sargasso Sea, located in the Bermuda Triangle area, for the composition of the algae in the two regions is quite different.
Some have taken to calling this relatively new phenomenon of sargassum accumulation between the coasts of Brazil and Africa, in the South Atlantic, the New Sargasso Sea.
Alfonso Aguirre Muñoz, former director-general of the Group of Ecology and Conservation Islands, said the new sargassum biomass originates along the Atlantic coast of Africa and the mouth of the Congo River and is swept along by a marine currents that circulate through tropical latitudes. It passes across the mouth of the Amazon River, where it is fed by the increasing outflow of nutrients, and along the northeastern coast of Brazil, finally reaching the Caribbean Sea and continuing on through th Gulf of Mexico to the coast of Florida.
New Sargasso Sea
Hypotheses about the origin of this New Sargasso Sea and its arrival to the Caribbean are many, but experts increasingly agree that several factors are probably at work.
Rosa Isela Rodríguez Martínez, one of the first scientists to study the behavior of this algae, points to the increase in ocean nutrients originating from the discharge of pollutants into the mouth of the Amazon River. Among the nutrients are algae “fertilizers” such as magnesium, calcium, phosphorus and nitrogen.
Sargassum swamps beaches, stains water brown-yellow, greatly alters coastal ecosystems
Too, increasing deforestation and agricultural production in the Amazon River Basin over the past decade is thought to be putting more sediment into the river and thus more nutrient into the river’s outflow to the sea.
Off the coast of Africa, meanwhile, Sahara Desert dust, which also contain some of these nutrients, gets blown into the eastern Atlantic, then flows along the westerly marine current toward the Americas. In addition, increasing ocean temperatures resulting from climate change benefit algae growth, analysts say. Caballero Vázquez says that the explosive growth of sargassum over the past decade could be the sum of all these factors.
Scientist say sargassum macro-algae contains heavy metals, which can be toxic in large quantities, and high concentrations of nutrients.
Caballero Vázquez says algae from the original Sargasso Sea are poor in nutrients, while those from the New Sargasso Sea have high concentrations of nutrients and heavy metals. Caribbean waters are historically “oligotrophic”, meaning they typically have a very low nutrient load, hence its picturesque blue color and legendary transparency. But when the sargassum algae reaches the coast, they completely transform ecosystems and landscape.
Visible and invisible evidence
In terms of environmental effects, the primary problem is algae rotting in the sea, which produces a foul odor and releases liquids known as “leachates” that load the water with nutrients.
“These leachates drain into the sea and form what we call the ‘brown tide.’ At this point there is already important bacterial growth in sargassum, and within this ‘brown tide’ the oxygen concentrations levels drop a lot,” Rosa Rodríguez said.
In marine zones with high sargassum concentrations and the brown tide effect, meadows of seagrass tend to die off because since they need oxygen and light to survive, Rosa Rodriguez said.
Seagrasses are highly important to the coast because they serve as refuges, habitat and food for hundreds of marine species. In addition, they protect the coast from erosion, reduce the sea’s strength during storms and hurricanes and serve as a valuable sink to store carbon.
In 2018, Rodríguez said, scientists began to register a rising death toll of marine species – fish, crustaceans, octopuses, sea cucumbers – in zones with high sargassum concentrations on the beaches. A study showed that in the accumulated sargassum along the beaches of Quintana Roo were found the corpses of 78 animal species.
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Gonzalo Merendiz Alonso, executive director at Amigos de Sian Ka’an, says the sargassum is also affecting mangrove forests, wildlife refuges, habitats and the breeding of hundreds of fish species.
Since 2015, some Caribbean countries have taken measures to mitigate the effects of sargassum on the coasts. In Mexico, the Secretariat of Environment and Natural Resources issued a series of guidelines for the treatment of algae. For example, burying sargassum in the sand, a recurring practice until 2018, is forbidden. Sargassum collection must be carried out with specified machinery, so that it does not damage sea turtles, and algae must be taken to a proper waste disposal site.
However, the coasts already show visible effects. Hydrogeologist Guadalupe Velazquez of the Research Center for Sustainable Development says that in the town of Puerto Morelos in Quintana Roo, beaches have suffered from serious erosion and compaction. That’s because in the process of removing algae, many pounds of sand are also taken away and because of the pressure from the continuous crossing of machinery.
“When there are meteorological phenomena, it can be seen how the sea is gaining more and more ground on the coast,” Velazquez said.
The problems caused by the excessive landfall of sargassum does not end when it is taken off the beach, because to date only one municipality, Puerto Morelos, has set up a final disposal site with a geomembrane to avoid the pollution of soil by leachates. Other municipalities, in the best of cases, dispose of the sargassum at sites specifically set up for this type of organic waste, located far from urban zones.
High sargassum concentrations are transforming Caribbean coasts, threatening economies and ecosystems.
Alejandro López Tamayo, president of the Centinelas del Agua organization, says that the Yucatan Peninsula region in Mexico has a system of porous karstic ground, with an aquifer a few yards deep. Without appropriate processing, the leachates released during the rotting of sargassum easily seep into the water table and the aquifer, polluting the soil and water, he says.
Another study led by the academic Rosa Rodríguez Martínez also shows the presence of polluting elements in the sargassum, such as arsenic, copper, manganese and molybdenum, which in high concentrations can be harmful for humans beings, plants and animals.
Scientists warn that, in the long term, the effects of sargassum in the main coastal ecosystems could devastate the Caribbean Sea and the economies of the region, which are highly dependent on their natural resources.
Mexico’s approach
For five years, the Mexican government has failed to contain or reduce the problem. At first, Quintana Roo’s government, municipalities and hotels were in charge of cleaning beaches. That entailed investments of tens of thousands of dollars to build barriers, buy machinery, pay workers and transport and dispose of the waste.
In 2019, Quintana Roo created a government advisory council to manage the sargassum, in conjunction with scientists and business owners. Several initiatives for the integrated management of sargassum were started, from monitoring and collection at sea and on the beaches, to final disposal and even industrialization, by turning the organic waste into useful byproducts. The proposed projects would be funded with joint contributions from the three levels of government.
But because of conflicts among the stakeholders and outrage arising from suspected interference from an official in the drafting of contracts, the main project, nicknamed Caribbean Shield, was discarded.
Manuel López Obrador, Mexico’s president, ordered the Secretariat to take charge of the issue. One of the first strategies implemented was the collection of sargassum in the open sea, following up on the advisory council’s recommendations. Five deep draft vessels were assigned to carry out this task.
Nevertheless, the support from the federal agency is minimal and comes with high operational costs. From 2019 to September 2020, only 304 tons of sargassum was collected in the sea, barely 1.6 percent of the 18,317 tons collected on public beaches by municipal city councils in Quintana Roo.
Workers from the municipality of Benito Juárez in Cancun, Mexico, remove sargassum from the beaches.
During seasons with a surge of sargassum, beginning at dawn hundreds of temporary workers hired by the city councils and hotels pick up tons of wet algae to keep it from rotting on the beach. “When the tourist comes to the beach, he has to see everything clean,” a crew chief yelled out to his workers.
Sargassum represents a serious threat to the Mexican Caribbean tourism industry, the most powerful in Latin America. “If a prompt solution to the problem is not sought, consequences for the future could be fateful,” Rodríguez Martínez said.
Quinta Roo alone receives 14 million visitors annually in a typical pre-Covid year, with a contribution to the national gross domestic product of more than $2 billion, according to reports from the Tourism Secretariat.
Destinations such as Cancun, Playa del Carmen, Tulum and Cozumel offer the beauty of their beaches as the main attraction to lead the Latin American tourism market. But at beaches with high sargassum concentrations, especially in the bays and reef lagoons where the algae becomes stagnant, the water color has changed from turquoise to brown, altering the landscape even when it is not the sargassum season. Examples of this phenomenon can be found on the coasts of Puerto Morelos and Xcalak, as well as the bays of Sian Ka’an.
Solutions still uncertain
Tourists traverse large accumulations of sargassum on the Yucatan Peninsula to reach the Gulf of Mexico.
Currently, there are several proposals to harvest and process the sargassum in the Caribbean, a measure that would solve part of the problem by transforming the algae into a resource with commercial value, according to promoters.
One of the most advanced projects is from the company Dianco Mexico, which plans to start operations in Cancun in mid-April to transform sargassum into biofertilizer. Another planned product of the company is cellulose.
CEO Héctor Romero says that the factory will have the capacity to process up to 600 tons of algae daily.
Other proposals suggest the algae can be used in the livestock feed industry, in the cosmetic industry or to generate biofuel.
But to Adán Caballero, the research available to date on the algae of the New Sargasso Sea is not enough to establish its potential use, because the contaminants it contains could represent a risk to public health.
“The original Sargasso Sea has several associated industries and large studies that support the use of its algae, but the studies we have on the sargassum affecting the Caribbean are still emerging,” he says.
Meanwhile, the tide of sargassum keeps rising.
This story was produced by InfoAmazonia with support from Internews’ Earth Journalism Network.