Discover the latest Caribbean sargassum forecast predicting 400,000 tons this season and its impact on coastal ecosystems, reefs and tourism.
Mexican coastal communities brace for a historic surge of sargassum seaweed this hurricane season after UNAM researcher Brigitta I. van Tussenbroek warned that an estimated 400,000 tons of the algae will arrive on the Caribbean coast this year. Of that total, around 100,000 tons could wash ashore along Mexico’s beaches, posing serious threats to tourism, fisheries and fragile coastal ecosystems.
In a recent article published in Gaceta UNAM, van Tussenbroek, who heads the Puerto Morelos unit of the Institute of Marine Sciences and Limnology at UNAM, reported that tropical sargassum stocks have swollen to at least 37.5 million metric tons. Some satellite data even suggest levels close to 40 million tons—nearly double the 22 million ton peak recorded in 2018. The current influx already began in May, and the 400,000 tons forecast for Mexico’s coastline represent just 10 percent of the total mass forming across tropical waters.
“Unless a major event like a hurricane disrupts these blooms, I’m certain we’re heading into an even worse stretch,” van Tussenbroek said, noting that July is likely to be critical, with high risks extending into August depending on oceanic nutrient levels and satellite algal bloom forecasts.
Van Tussenbroek characterized this new high as “a total disaster,” emphasizing the algae’s cumulative damage since 2015. She explained that sargassum thrives on excess nutrients washed from land into the sea, then drifts toward beaches where it degrades water quality, smells foul as it decomposes and smothers nearshore habitats.
Coastal reefs once admired for their turquoise clarity now suffer under thick mats of rotting sargassum that block sunlight and encourage harmful bacteria. “Reefs already weakened by algae arrivals and coral diseases have seen massive die-offs,” said van Tussenbroek. “Few coral colonies recover once they’re buried under this organic burden.”
Seagrass meadows, vital for stabilizing sediments and providing fish nurseries, also lose their protective capacity when layered with decomposing seaweed. Van Tussenbroek warned that mangrove roots, crucial for coastal resilience, may suffer from reduced oxygen levels in the surrounding mud, threatening shoreline defenses against storms and erosion.
Local authorities have begun deploying heavy machinery and community brigades to clear beaches preemptively, drawing on a recently approved disaster relief fund. Yet the scale of this season’s sargassum influx may overwhelm existing resources.
“This isn’t just a beach-cleaning problem,” van Tussenbroek stressed. “We’re looking at long-term shifts in our coastal ecosystems.” She urged federal, state and municipal governments to coordinate monitoring, invest in early-warning systems and support research into sustainable removal techniques.
As the Caribbean coast prepares for a challenging season, scientists continue to refine satellite models and on-site surveys to track sargassum movements. Van Tussenbroek and her team at UNAM plan to expand their monitoring network, hoping to alert hotels, fishers and residents when blooms threaten landfall.
With communities on high alert, the coming weeks will reveal whether coordinated action can mitigate the worst impacts of this record seaweed invasion—or whether Mexico’s iconic Caribbean coast will face another summer defined by mountains of decaying sargassum.
