Chapter 1: The Sargassum Invasion

The elegant resorts of Puerto Morelos come into view as the captain jovially sounds the horn to alert the crew of the impending sight—a vast, golden-brown expanse stretching endlessly. Suddenly, the crystal-clear waters of Mexico’s Caribbean are replaced by dense mats of seaweed, accompanied by a sulfurous odor.

This is precisely where the crew of a specialized Sargassum collection vessel aims to be. Operated by Grupo Dakatso, a coalition of five enterprises developing new seaweed collection technologies, this small catamaran features a unique conveyor belt at the bow, designed to scoop up seaweed from the water and funnel it into large mesh bags. Amid the cacophony of the engine, the crew communicates through whistles and hand signals as they rapidly fill bags, each capable of holding 300 kilograms (660 pounds), within mere minutes.

Since spring 2018, Mexico’s Caribbean coast, alongside shorelines in 19 other nations, has experienced an overwhelming influx of Sargassum seaweed. Tourists anticipating pristine beaches instead encounter endless heaps of rotting vegetation. While some amount of this brown macroalgae is typical along Caribbean shores, the extreme blooms have been growing both in size and frequency over the last decade. The bloom recorded last year is considered the worst in the region's history, prompting efforts not only to manage the ecological disaster but also to find ways to leverage it.

“The future generations will face severe challenges if we remain idle. Sargassum isn’t going away.”

Typically, Sargassum makes its way to the Caribbean from its namesake sea in the eastern Atlantic. However, researchers suggest that the surge in 2018 originated from a new source: the equatorial waters between Brazil and West Africa, where pesticide and fertilizer runoff from the Amazon and Congo Rivers nourished the algae bloom. This problem has been exacerbated by climate change, with rising ocean temperatures accelerating the growth of the seaweed, according to Brigitta van Tussenbroek, an ecologist at the National Autonomous University of Mexico in Puerto Morelos. Deforestation in the Amazon rainforest contributes significantly as it increases runoff and is a major factor in climate change.

“We humans are responsible for the Sargassum issue,” states Dagoberto Ruiz Lavín, the general director of Grupo Dakatso, which has been contracted by local hotels and the government to clear the seaweed. “If we don’t act, future generations will be much worse off. Sargassum will continue to arrive.”

Under normal circumstances, Sargassum is a beneficial part of the ocean ecosystem. However, in excessive amounts, it poses numerous threats to coastal environments. The thick mats block vital sunlight from reaching coral reefs, leading to disease or death. As the seaweed decays, bacteria absorb oxygen from the water, releasing nitrogen, phosphorus, and other nutrients in significant quantities. If left to rot on land, as seen on Mexico’s beaches, these nutrients risk contaminating groundwater. In the Yucatán Peninsula, where fresh water relies on a unique underground river system, this contamination is a serious concern. While seaweed can absorb carbon dioxide from the atmosphere, its environmental benefits are only realized if it is harvested and processed in a manner that sequesters the CO2 permanently.

Van Tussenbroek notes that the cumulative effects of Sargassum overgrowth can disrupt the balance of ecosystems. For instance, Sargassum can kill the seagrasses that stabilize sand, accelerating beach erosion. She estimates that following the 2018 crisis, the local ecosystem might take anywhere from 10 to 50 years to recover, but another significant influx or a major hurricane could lead to irreversible changes.

Currently, Mexico’s response to the Sargassum crisis has largely been limited to marine barriers, akin to those used for oil spills, and beach clean-up crews armed with rakes and wheelbarrows. This endeavor resembles a Sisyphean task: just as the beach is cleared, another tide of seaweed is never far behind. José Ángel Durán Désiga, a young but weary municipal bureaucrat, outlines the challenges faced by the government from his office near Playa del Carmen's beach. As the director of the Office of Environment and Climate Change in Solidaridad municipality, Durán Désiga grapples with the Sargassum dilemma. Unfortunately, local officials lack the necessary resources and authority to make substantial progress due to Mexico’s centralized governance.

“The coast will persist, but it will belong to a different ecosystem,” Durán Désiga asserts. “It might lack reefs. There could be new and different types of fish, making it harder for tourists to enjoy the water.”

Even if seaweed collection efforts could be significantly expanded, a major question looms: what to do with the collected seaweed?

Seaweed is already a common ingredient in cosmetics and food additives. Energy companies, including ExxonMobil, are investing in research on microalgae—a microscopic organism that can create red and brown tides—with hopes of developing a low-emissions transportation fuel by extracting oil from it. Conversely, macroalgae like Sargassum haven’t garnered as much attention for biofuel production, partly due to the challenges associated with large-scale farming. Testing has been conducted on using Sargassum for biogas through anaerobic digestion, which involves decomposing the seaweed in a tank to capture gases like methane for energy. However, Sargassum contains a polymer known as lignin that complicates methane production. Currently, Mexican researchers are exploring solutions to this issue.

At the Yucatán Center for Scientific Research, a government-funded lab complex nestled in a lush jungle near Mérida, the scent of Sargassum permeates the air. David Valero, a PhD researcher specializing in anaerobic digestion, is part of a team focused on creating a more efficient seaweed-to-biogas process that can handle Sargassum directly from the beach or sea with minimal processing to eliminate sand or plastic.

Valero and his colleagues are working to accelerate the seaweed breakdown process by pre-treating Sargassum with a local fungus, alongside enhancing the efficiency of their bioreactor using activated carbon. He estimates that each ton of Sargassum could yield around 720 kilowatt-hours of energy or 63,600 liters (16,800 gallons) of natural gas.

Meanwhile, biologist Francisco Larqué Saavedra has different ideas for Sargassum. With a long-standing interest in sustainable food production, he has spent the last 30 years cultivating a bank of native mushroom species. In 2018, he began exploring a strain that could thrive in seaweed. His team has successfully grown mushrooms using Sargassum that has been pasteurized and processed, producing approximately 800 kilograms of edible mushrooms for every metric ton of dried seaweed. Larqué Saavedra envisions hotel owners establishing on-site mushroom farms to utilize the seaweed accumulating at their properties while generating both food and job opportunities.

However, the region is far from realizing this vision. The Association of Hotels of the Riviera Maya reported a 10% decline in occupancy last year due to the seaweed issue. Tourism represents over 8% of Mexico’s GDP, with Quintana Roo, the Mexican state on the eastern Yucatán Peninsula, hosting 40% of the nation’s foreign visitors. The hospitality and restaurant sectors contribute to 25% of Quintana Roo’s GDP, leaving workers in those industries with limited options in other fields. Fewer tourists translate to diminished government revenue, which in turn reduces funding for Sargassum removal efforts. The economic fallout from declining tourism could bolster drug cartels, whose violence has increasingly encroached on the tourist areas of the peninsula.

Thus, by choking off tourism, the seaweed simultaneously deprives efforts to combat its encroachment.

Lauren Zanolli is a freelance journalist primarily focused on the intersections of food, technology, business, and human health. She is based in New Orleans, Louisiana, and can be reached at [email protected].

Originally published at www.technologyreview.com on April 24, 2019.

Chapter 2: Raising Awareness and Solutions

The first video titled "Cancun's Riviera Maya: The Big Sargassum Problem Killing the Tourist Industry" delves into the severe challenges posed by Sargassum and highlights the impact on tourism in the region.

The second video titled "The Seaweed Situation in the Riviera Maya and a Call to Awareness About Our Environmental Impact" emphasizes the environmental implications of Sargassum and the urgent need for collective action.