The Pungent Reality of Sargasso
The nauseating smell wafts through the air, sending a shiver down the spine. It resembles the odour of countless rotting eggs left to decay by the shore. What should be a picturesque beach with white sand and turquoise waters in the Mexican Caribbean has instead become a repugnant scene, which not only undermines the tropical experience but also serves as a stark reminder of the changes we impose on the ocean and its people.
On the coast of Quintana Roo, Mexico, a man hurriedly emerges from a patch of brown seaweed. Dressed in thin clothing and a wet cap, his bare feet are wrinkled and calloused, with only a few nails clinging on. He crosses the street, retching after having spent long hours under the sun, immersed in a dark, acidic broth.
The first significant influx of sargasso arrived on the shores of cities like Cancún, Puerto Morelos, Playa del Carmen, Tulum, and Mahahual in 2014, bringing with it a new occupation: the sargassum collector.
Since that time, these workers have reported symptoms ranging from intense itching, skin irritation, and rashes to vomiting, hair loss, sleep disturbances, and even respiratory difficulties.
Health Risks of Sargasso Collection
A scientific study published in April 2026 documented, in real-time, the exposure to hydrogen sulfide, a toxic gas released by the algae as it decomposes, which emits a characteristic rotten egg smell. The findings indicate that sargassum collectors inhale dangerously high levels of this potentially lethal gas.
The research was led by Rosa Rodríguez Martínez from the Institute of Marine and Limnology Sciences at the National Autonomous University of Mexico (UNAM) in Puerto Morelos, along with scientists from the University of São Paulo in Brazil and the University of Victoria in Canada. The researchers equipped workers with portable sensors, designed by the Academic Service for Meteorological and Oceanographic Monitoring, placed at chest height to monitor the amount of gas inhaled during their workday.
The legal limit for an eight-hour workday is one part per million: one molecule of hydrogen sulfide for every million molecules of air. While this may seem minimal, the gas is so toxic that the law prohibits higher levels. The sensors recorded that nearly half of the workday, 46.3% of the time, workers inhaled levels above this threshold, with peaks reaching up to 50.8 ppm—more than fifty times the permissible limit. Rodríguez captures the risk with a vivid analogy: “It’s not the same to be stung by a bee as to be stung by fifty.”
The Decomposition Dilemma
As sargasso decomposes on the shoreline, it becomes a workplace hazard and a public health risk, warn the scientists. The current management efforts, they add, are insufficient to protect both ecosystems and the individuals who face this crisis head-on. “There is an urgent need to implement Mexican regulations through prevention protocols, continuous monitoring, and protective equipment to safeguard workers’ lives,” the study highlights.
As the mass arrivals of sargasso set records each season, the health of those who collect it is overshadowed by the necessity of work and the precarious conditions they endure. This year, another record is anticipated, not only in the amount of sargasso but also in the biomass accumulated in decomposition.
Walking along a Quintana Roo beach, I sought out workers willing to speak. I approached politely, receiving some morning greetings, but little more. After several unsuccessful attempts, it became apparent that my presence was unwelcome. Most averted their gaze or looked at me distrustfully. Finally, one agreed to talk:
—“Are you informed of the risks when you’re hired?” —I asked.
—“Nothing. They only ask if you can handle the tough work,” replied a seasoned sargassum collector with a decade of experience.
—“Is it risky?”
—“It’s the job, and it has to be done. Otherwise, there’s nothing to eat.”
Historical Context of Sargasso
Sargasso is not a new phenomenon in the sea. When Christopher Columbus crossed the Atlantic in 1492, he noted in his journal the floating masses of seaweed that covered the waters of a sea later named the Sargasso Sea by Portuguese sailors. Out there, the algae create a haven, forming mobile islands that shelter turtles, fish, and birds. What is new is the scale and prolonged presence along the Caribbean coasts.
According to Rosa Rodríguez, sargasso represents the ocean’s response to our actions. “The sea is collecting all the rubbish we dump into it and returning it to us, saying: ‘Here, you deal with your waste.’” This metaphor is backed by measurable data.
Brian Lapointe, an oceanographic researcher at the University of Florida, maintains that “sargasso serves as a barometer of how humans are altering the planet’s nitrogen cycles.” Both he and Rodríguez refer to the excess of fertilizers and wastewater we release into the sea, which the algae readily absorb, alongside climate change that raises temperatures and alters currents.
Those who experience this phenomenon daily echo their sentiments: “I believe nature is already charging us for the pollution we inflict upon the poor sea,” says an anonymous sargassum collector.
Rising Tides of Sargasso
In 2011, satellite images detected an unprecedented mass in the Tropical Atlantic. By 2014, a monumental portion first reached the shores of the Mexican Caribbean, and since 2018, the influxes have transformed from an exception into a routine occurrence. “There used to be alternating high and low years,” Rodríguez explains. “Now, as we saw in 2025, growth is exponential.”
The 2025 upwelling was the most severe recorded. Between January and August of that year, the biomass in the Mexican sea was estimated to weigh 3.4 million tons—more than double the previous record of 1.4 million tons in 2022. “In 2026, month by month, we are breaking the records of 2025,” Rodríguez adds. “This is very concerning, as it indicates an increasing trend that will likely continue for some time.”
During a morning conference on July 30, the head of the Ministry of Environment, Alicia Bárcena, provided figures to illustrate this surge. She stated that this year has seen four times more sargasso than in 2025 and 27 times more than the historical average. The causes, she explained, align with those identified by scientists: the excess nitrates and phosphates from industrial agriculture that fertilize the algae in the tropical Atlantic.