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How To Handle A Massive Seaweed Invasion? Yucatán Towns Get Creative

Men walk between the sargassum toward a boat in Playa del Carmen, Mexico, in May.
Victor Ruiz
Men walk between the sargassum toward a boat in Playa del Carmen, Mexico, in May.

The water off the coast of the Riviera Maya was warmer than I expected, but far murkier. Endless pieces of seaweed, floating on and just below the surface, wrapped themselves like wet masking tape around my flippers and mask as I examined the second-largest reef in the world.

"It's the sargassum," my divemaster from Tulaka Diving told me resignedly. "It's coming over from Brazil and getting worse every year."

Sargassum, a brown macroalgae, is wreaking environmental havoc in the Mayan Riviera, located along the Caribbean coastline of Mexico's Yucatán Peninsula, as well as the Caribbean, coastal South America and Florida. The seaweed invasion is being fed by modern agricultural practices. As the Amazon is deforested to make way for farming, fertilizer used on that land is running off into the Amazon River and the ocean, encouraging blooms. Fertilizer runoff from other parts of the world is also fueling the problem.

The seaweed isn't just grouping in the water, but washing up in unsavory masses on beaches from Cancun to Tulum. There, it stinks like a cracked Easter egg that someone forgot to hard boil. The odor is a tourism problem. Local governments and resorts are struggling to combat sargassum with all manner of measures, which include employing sargaceros to rake it up manually.

Grand Residences Riviera Cancun, located in Puerto Morelos, collects the sargassum from its beach every morning with a special lightweight crawler that simultaneously filters out the sand. From there, the seaweed dries, then passes through a crusher. The staff then distributes the product like dirt throughout the property's grounds; since the odor is gone, guests don't even notice.

But sargassum is also a food chain nemesis. "It suffocates the reef, suffocates the beaches, and suffocates the turtles nesting," says Denis Normandin, a partner in the at-sea sargassum harvester called The Ocean Cleaner.

Ricardo Diaz agrees with that assessment. He's the project director at Aventuras Mayas, an environmentally conscious tour company, and the founder of the G.R.E.A.T. (Green energy, Recycling, Ecological toilets, Aqua protectors, Trash management) People Project.

"The massive arrival of sargassum to the Mexican Caribbean shores has resulted in the death of different types of fish, sea cucumbers, sea urchins, and crabs, among others," Diaz says. Marine scientists from the National Autonomous University of Mexico, based in Puerto Morelos, say that sargassum is killing dozens of species in the Quintana Roo region.

Economically speaking, Diaz says, "the most affected are lobster fishermen, who have seen a reduction in supply."

This past January, the Riviera Maya News reported that the Tulum lobster catch was 80% below an estimated 200-ton target, with only one month to go until the season ended. This year, the season began in July and will end in February 2020. Catch statistics aren't yet available, but researchers expect this year's sargassum invasion to be larger than in years past.

The seaweed wads, thick as yoga mats, are doing untold damage to tidal and reef ecosystems by disrupting the photosynthesis cycle and depleting the oxygen in the water in places. Normandin, along with partners Francesco Maselli and Denis Jimenez, came up with one approach to tackle the problem: The Ocean Cleaner. It's a boat and trailer that sucks the sargassum up from the surface. After it's collected, Normandin says they turn it into "a compost mixed with food scraps from hotels." Maselli says that a single boat-trailer conveyor can harvest "up to 500 metric tons of sargassum from the sea per day, depending on conditions."

The tide, however, is currently against them: Experts say conditions are ripe for overgrowth, and they predict the Riviera Maya will receive between 800,000 and 1 million tons of sargassum this year.

Sargassum islands, formed by ocean currents called gyres, are entire ecosystems of their own. They offer shade from the sun; food for both fish and ocean birds; safety and camouflage; and even transportation for sea creatures as the mat drifts. A natural habitat for sea horses, crabs, turtle hatchlings and other juvenile sea creatures, sargassum islands are, when in balance, a healthy part of the ocean's life cycle.

More recently, though, "a recurrent great Atlantic sargassum belt (GASB) has been observed in satellite imagery since 2011, often extending from West Africa to the Gulf of Mexico," according to a study recently published in Science. One of the authors of that study, Brian Lapointe, a research professor at Florida Atlantic University's Harbor Branch Oceanographic Institute in Fort Pierce, Fla., calls Denis Jimenez's Ocean Cleaner boat design "an innovative and efficient tool to help moderate the sargassum influx."

Still, the GASB is more than 20 million tons – and growing. Normandin estimates that the seaweed, being fed en route from Africa through Brazil, doubles in volume every 18 days.

Others are also experimenting with new uses for all that seaweed. The Sargasso Industrial Association, a collective of five private-sector companies, is turning the macroalgae into, among other things, biofertilizer for food crops. It's already been tested on vanilla, cocoa, sugarcane and tomato crops.

Meanwhile, the Puerto Morelos Protocol, a joint effort between the town government and civic leaders to deal with sargassum, passed what is essentially a tourist tax to pay for clean-up initiatives. All hotels must charge guests a fee of about 25 pesos [U.S. $1.28] per visitor per night, says Daniela Trava Albarran, the general manager for Grand Residences. With 7,000 hotel rooms in Puerto Morelos and an average 85% occupancy rate during the tourist high season, which lasts from November through April, that's a generous chunk of change that can could model sustainability for other towns along the Riviera Maya and beyond.

These efforts are seeing results. As of Friday, Puerto Morelo's beaches were declared free of sargassum by municipal president Laura Fernandez Piña. But that, of course, can change by the day.

Aside from lobster, chefs in the region haven't necessarily noted rising fish prices or falling supply – yet. But that's largely because fishermen are following the fish with the mobility to leave de-oxygenated areas. Executive Chef Rafael Borbolla, who works at Grand Residences, which grows much of its own herbs and vegetables and buys other ingredients as locally and seasonally as possible, says he is going for deep-sea varieties. Thus he is avoiding species that would be in short stock or diseased from an excess of sargassum.

"The majority of my seafood and fish supply is sourced from the Gulf of Mexico, and the catch there has not been affected," he says. That may change, however, as sargassum, captive to currents, begins to hit other regions of the world, including Florida's coast.

Sargassum is also, apparently, edible. Jabib Chapur, vice president of food and beverage at Palace Resorts, recently started to experiment with the seaweed for dishes in his test kitchen. "Basic studies were carried out on foods such as those with crunchy textures, salsas, and gummies, which resulted in very good sensory characteristics," Chapur says. But he's not putting sargassum on the menu anytime soon, he says, because he can't guarantee that it's completely nontoxic.

It's possible that the sargassum could contain high levels of bacteria or heavy metals. Recently, high levels of enterococci were found in the sand in Florida's Key Biscayne, a barrier island, where sargassum is tilled into the beach. Scientists from University of Miami and Nova Southeastern University believe the seaweed encounters the bacteria from humans as it nears the shore. These levels ramp up as the seaweed piles up and steams in the heat, becoming the ideal incubator.

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Jen Karetnick