Tulum is the kind of beach that vacation dreams are made of: Turquoise water, white sand and an ancient Mayan pyramid overlooking it all.

But an unwelcome visitor has invaded this Caribbean paradise: Sargassum, a thick seaweed that has turned the crystalline water brown, filled the air with a rotten-egg smell and washed up on the beach in enormous piles.

It is an almost postcard-perfect day at the tropical beach on the southeastern coast of Mexico. But hardly anyone is swimming in the water, and few people are relaxing on the sand.

Aside from the hardy few willing to swim 50m to reach the clear water beyond the seaweed, the tourists have mostly taken refuge at their hotel swimming pools.

“I had no idea how bad it was,” says Chase Gladden, 28, an American business executive from San Francisco, as he walks along a 10m-wide carpet of sargassum stretching to the horizon.

“And if they don’t take it away, it starts to smell – it smells really bad. I can imagine you would take a big hit to tourism if people don’t want to come here because they don’t want to have to deal with this much seaweed,” he says.

Livia Vendramini, a 26-year-old tourist from Sao Paulo, Brazil, says her vacation has turned “very sad”.

“We came here for a blue, crystalline sea,” she says.

She and the two friends travelling with her abandoned their original hotel, in Playa del Carmen, because of the seaweed there.

Tonnes of seaweed are invading the beaches in Mexico, upsetting the country’s tourism industry.

But the situation is not much better in Tulum, 65km south. So they have decided to hire a private boat to take them to another beach that has been spared the seaweed invasion.

Ecological and economic disasterOnce it reaches shore, sargassum begins to decompose, sucking oxygen out of the water and cutting off sunlight to the marine life below.

It devastates the ecosystem that gives the Caribbean its signature turquoise colour. Scientists do not know if the damage can be reversed.

“It could turn into an ecological and economic disaster,” says Marta Garcia, a Spanish scientist at the Marine Sciences Institute at Mexico’s largest university, National Autonomous University of Mexico (UNAM).

Mexico is not alone. Other spots in the Caribbean have also been invaded by sargassum, including Barbados, Guadeloupe and Bonaire.

The phenomenon would take a toll on the tourism-based economy, denting the revenues of hotels, airports and the government.

Passenger arrivals in Cancun, Mexico’s second-busiest airport, were down 1.8% from January to April versus the previous year, it said.

Sailors have long known of a “Sargassum Sea” in the north Atlantic, off the coast of the United States. But researchers say this seaweed comes from a new sea of sargassum in the southern Atlantic, between South America and Africa, that was first detected in 2011.

Scientists believe it is being fed by global warming, deforestation and runoff water full of sewage, agricultural waste and other nutrients.

“It has more nutrients than the original Sargassum Sea,” says Brigitta Van Tussenbroek, a Dutch researcher at UNAM.

“This is all created by humans. It’s not something natural.”

Residents removing sargassum in Puerto Morelos. This needs to be done daily.

Shovels, boats, ingenuitySargassum is unfortunately “here to stay”, says Carlos Gosselin, an architect and hotelier in Puerto Morelos, 100km north of Tulum in Mexico.

He runs Puerto Morelos Protocol, a group of experts and tourism professionals trying to fight the seaweed invasion on Mexico’s prized Mayan Riviera.

According to the group, the first wave of sargassum arrived in 2015. The problem exploded in 2018, when 24 million cubic meters washed ashore – enough to lay a meter-thick carpet of seaweed covering 3,000 football pitches.

Puerto Morelos has installed special netting to keep sargassum from reaching the beach, though it is not 100% effective. It also uses a boat to scoop up the seaweed.

Thanks to those measures, 13km of the town’s 18km of beach have been spared, according to Gosselin.

“Puerto Morelos has become a laboratory to test what works or doesn’t work,” he says.

Several entrepreneurs have meanwhile come up with creative uses for the seaweed, making shoes, books and even houses from it.

Other residents are tackling the problem the old-fashioned way, clearing the beach every morning with shovels and rakes.

“We have no choice. We have to act so tourists keep coming,” says Arlette Escudero, 34, her rake in hand. – AFP Relaxnews