It’s Even Worse: Record Sargassum Deluge Chokes Caribbean Beaches

Quintana Roo took in more sargassum in three days than what would have arrived during a whole month last year.

Record amounts of ugly, unsightly sargassum seaweed are washing ashore across the Caribbean, hitting 37.5 million metric tons (41.3 million short tons) in May 2025. The thick brown algae mats are overwhelming beaches from Puerto Rico to Mexico’s Yucatán Peninsula, threatening the tourist economy and public health.

Along the Mexican Caribbean coast in Quintana Roo state, 68% of beaches being monitored reported moderate to excessive algae levels on Saturday. The area took in more sargassum in three days than what would have arrived during a whole month last year.

An estimated 37,600 tons of sargassum will arrive along the Quintana Roo coast this year, according to the Mexican Navy. The state encompasses major tourist destinations including Cancún, Playa del Carmen and Tulum.

The surge threatens to disrupt tourism in regions that rely heavily on pristine beaches. Hotels and coastal businesses face mounting cleanup costs as the rotting seaweed produces a foul smell and potentially harmful gases.

Mexico Bears Heavy Burden

In 2024, 125 million pesos were invested in Quintana Roo to collect 37,000 tons of algae, mobilizing 300 naval personnel, specialized vessels, and containment barriers. Despite these efforts, beaches have already lost between 10 and 20 meters (33 to 66 feet) of sand in areas like Puerto Morelos.

“We’re analyzing currents and wind patterns to determine the best way to collect the largest amount before it reaches the beach,” said Vice Admiral Jorge Muñoz Hernández of the Mexican Navy.

The economic impact is significant. Tourism in Quintana Roo declined 11.6% from 2016 to 2019 due to sargassum, according to the Inter-American Development Bank. Hotels mobilize crews at dawn to clear beaches, adding unbudgeted operating costs.

Health Concerns Mount

Decomposing sargassum releases hydrogen sulfide gas and ammonia, which can cause respiratory, skin, and neurocognitive symptoms. The toxic exposure typically occurs approximately 48 hours after it washes ashore.

Significant exposures (50-400 ppm) may produce difficulty in breathing, agitation, confusion, nausea and vomiting, elevated blood pressure, and loss of consciousness. French Caribbean officials have temporarily closed schools due to dangerous gas levels.

Health officials recommend people with respiratory conditions avoid affected beaches. While the seaweed might look unpleasant, health experts advise beachgoers that the Sargassum isn’t usually harmful to humans, though small creatures in the seaweed can cause skin irritation.

South Florida beaches face their own challenges. Miami-Dade County spent more than $3.9 million on sargassum cleanup last year and has requested an additional $2 million from the state. The City of Key West spends about $1 million annually on sargassum cleanup.

In Miami, sargassum removal accounts for $9 million of the $11 million beach maintenance budget each year. County crews typically clear beaches each morning before tourists arrive, but afternoon tides often bring fresh deposits.

Sargassum Response Intensifies

Caribbean governments are implementing various strategies. Mexico has deployed floating barriers and specialized collection vessels. More than 500 Navy personnel are operating in shallow and deep waters to intercept sargassum before it reaches the coast.

Scientists link the crisis to human activities. Studies have pointed to pollution that the Caribbean region itself has done little to contribute to, including fertilizer runoff from Amazon Basin agriculture and industrial wastewater.

The phenomenon has affected 43 countries since large-scale arrivals began in 2011. The sargassum invasion has worsened since it exploded in the region in 2011, with scientists predicting 2025 could match the worst years on record.

Innovation efforts are emerging. Mexican entrepreneurs are developing ways to convert collected sargassum into building materials, biofuel and fertilizer. These initiatives offer hope for turning an environmental challenge into an economic opportunity.

The crisis highlights the interconnected nature of ocean health and regional economies.

Additional information about sargassum monitoring: sargassummonitoring.com.