Seaweed invasion hits Mexico
It started washing ashore in the Caribbean eight years ago, the smelly, yellow-brown seaweed known as sargassum. Then, just as mysteriously, it disappeared.
Now the avalanche of algae is becoming an annual event – with increasingly dire consequences.
This year, tons of the seaweed have fouled white-sand beaches from Miami to Mexico’s Mayan Riviera. Local officials are fretting about economic fallout. Scientists are warning of harm to the largest reef system in the Americas. In some places, the famously clear Caribbean water turns so murky it resembles gas-station coffee.
“It’s a little bit disgusting,” said Sara Fargeas, 29, a French tourist, wrinkling her nose at the stench from piles of decaying sargassum.
Fargeas and her husband were sunbathing one recent day on Playa Paraiso in the Mexican resort of Tulum, but it was anything but paradise. The water was too choked with bristly weeds to swim. “It’s disappointing,” she said.
The scale of the sargassum invasion is immense. In the past three months, more than 57,000 tons has been raked and scooped up on Mexico’s Caribbean coast alone. Even the Mexican navy has joined the battle, sending ships to fish the seaweed out of the water.
“You reach a point where you can’t keep up,” said Lucila Rodriguez, who manages a beachfront luxury-tent hotel in Tulum. By mid-July, business was so slow the hotel closed its restaurant.
The sargassum is highly unpredictable, its movement dependent on the winds and currents. In late July, the onslaught of seaweed suddenly eased along the Mexican coast, disappearing in some areas. But by mid- August, it was again sullying many of the country’s loveliest beaches.
Sargassum has been noted since the days of Christopher Columbus. But until recently, it stayed largely in the expanse of the North Atlantic off the U.S. coast known as the Sargasso Sea.
Scientists were stunned this year to see the algae had grown so explosively that it had formed a 10,000-km archipelago spanning the Atlantic, from West Africa to the Gulf of Mexico.
The sargassum has been inundating coasts from Florida to the French Caribbean. But this year, it’s hit Mexico particularly hard, inflicting pain on everything from $800-a-night hotels to flipflop-casual beach restaurants.
“Who’s going to eat here with the smell?” asked Manuel Vasquez, 36, a waiter at one such restaurant in Playa del Carmen. A rotten-egg odour wafted from piles of blackened seaweed.
Scientists worry the damage could go well beyond the tourist industry. They say the coastline itself could be in jeopardy. That’s because sargassum is weakening the coral reefs that serve as a buffer to waves, and the sea grass that anchors the sand.
That means future hurricanes could take increasingly big bites out of Caribbean beaches, said Brigitta van Tussenbroek, a marine biologist at Mexico’s National Autonomous University.
“It’s still really difficult for people to understand the magnitude of the problem,” she said.
If anyone understands the size of the problem, it should be the government of Quintana Roo, home to Cancun and the lush, 70-mile Riviera Maya. The state’s beaches and ancient ruins pull in around $14 billion a year – more than half of Mexico’s tourism earnings.
Officials here have declared a state of emergency – they’ve called sargassum an “imminent national disaster” – and are spending $30 million to remove it.
The state tourism minister, Marisol Vanegas, says there haven’t been mass cancellations at beach hotels. But along the Riviera Maya, businesses have been hit hard – even the fanciest properties.
One resort north of Tulum charges upward of $700 a night. It’s 50 acres of pure luxury, including a jungle crisscrossed with pristine paths and spacious rooms with champagne bars and solariums.
The property hugs a quiet white-sand cove, where the water is normally “as clear as a swimming pool,” its manager said. But one recent sunny day, workers with rakes were fighting a losing battle with the yellow-brown seaweed lapping up on the beach.
The hotel normally takes in around $50,000 a week in the summer, the manager said, but revenue in recent months has dropped by more than half. He asked that neither he nor the hotel be identified, to avoid further cancellations.
Scientists are only beginning to figure out what’s causing the massive bloom. A key culprit, they believe, is the increased flow of nutrients such as nitrogen and phosphorus into the ocean. Those are superfood for sargassum. One suspected source is fertilizer washed into the Amazon and then the ocean, due to increased farming and deforestation in Brazil. But nature could also be contributing to the sargassum bloom – with strong winds churning up nutrient-rich material from the ocean floor off West Africa.
Some scientists theorize that climate change is a factor, but others minimize it, saying the algae grows more in years when water is cooler.
It’s difficult to predict which beaches will be hardest hit. In mid-July, for example, Cancun had relatively little, while Tulum was clobbered.
But there’s little doubt among scientists that the onslaught will continue. As the algae dies off each fall, it leaves behind seeds that bloom the following season.
“Most years in the next decade we will see a lot of sargassum,” said Chuanmin Hu, the oceanographer at the University of South Florida who led the study mapping the giant sargassum belt.
In the open ocean, researchers say, sargassum can be beneficial, providing a habitat for fish, crabs and turtles.
But once it approaches the shore, everything changes.
“It’s a major socio-ecological catastrophe,” said Jesús Ernesto Arias, who analyzesMexico’s coral reefs at Cinvestav, a governmentbacked research centre.
The mats of algae block the light that corals need to grow. And as the sargassum decomposes, it releases hydrogen sulfide and ammonium, which kill flora and fauna in the sea. Researchers recently found that at least 78 species had been affected, with fish, sea cucumbers, crabs and other marine organisms dying.
Scientists suspect the seaweed is contributing to the spread of white syndrome, a disease that has destroyed 30 per cent or more of some coral species in Mexico over the past year.
But that’s not all. The sargassum kills sea grass – sort of an underwater meadow that holds sand and sediment in place. If both coral reefs and sea grass are damaged, hurricanes can whisk away bigger chunks of beach.
“We have a scenario of losing the line of the coast,” Van Tussenbroek said.
More than 10,000 workers and volunteers have been furiously raking, scooping and hauling the sargassum from Mexico’s beaches this year. Floating barriers have been installed to try to trap the weed.
The navy has deployed two ships to capture sargassum in giant nets.
“We wound up with the most complicated part” of the job, said Rear Adm. Enrique Flores Morano, who is commanding the anti-sargassum operation. That’s because farther from the shore, the algae often moves in thin strands that are difficult to trap. Only around 287 tons of sargassum have been collected in open seas so far, less than one per cent of the total.
Mexican officials have boasted of the success of their cleanup operations.
“I hope that in short order, we’ll be able to say that the problem is solved, although of course it will require constant attention,” President Andrés Manuel López Obrador told reporters this month.
But researchers say the algae was simply swept to other areas by climatic conditions. It’s been returning to some beaches in recent days.
“It’s very likely that huge amounts of the sargassum will return next year,” said Arias, the biologist. “This is a multinational problem. And it’s critical.”