2025 May Bring Worst Sargassum Surge to Mexican Caribbean

Mexico City, Mexico — The year 2025 may set a new record for massive sargassum arrivals on the beaches of the Mexican Caribbean, according to a warning from the National Autonomous University of Mexico (UNAM). If current conditions persist, the volume of this macroalgae could surpass even the levels recorded in 2018, which remains the worst year for sargassum influx to date.

Unprecedented Sargassum Accumulation

Data from the Optical Oceanography Laboratory at the University of South Florida shows that as of May 2025, approximately 37.5 million tons of sargassum were detected floating in the Great Atlantic Sargassum Belt, a concentration zone that has been expanding.

Brigitta Ine van Tussenbroek, a researcher at UNAM’s Institute of Marine Sciences and Limnology, emphasized that this phenomenon poses a critical threat to coastal ecosystems, particularly seagrasses, which are essential for beach stability and the reproduction of various marine species.

“Sargassum forms barriers that block sunlight, alter the water’s chemical processes, and suffocate seagrasses as it accumulates and decomposes in the littoral zone,” explained Van Tussenbroek, who leads the Seagrass Laboratory. This research center studies the effects of sargassum on underwater ecosystems and its relationship with coastal erosion.

Ecological and Economic Consequences

The disappearance of seagrasses directly impacts key species such as shrimp, fish, and lobsters, while also leaving beaches more vulnerable to storms and waves due to the loss of sediment retention provided by these plants.

Through controlled cultivation systems, Van Tussenbroek’s team has studied how sargassum reacts to variations in temperature, salinity, and nutrients. One of the most significant findings is that under favorable conditions—28°C temperature, 30 units of salinity, and a combination of nitrogen, phosphorus, and iron—the macroalgae can double its biomass in just five and a half days.

Complex Dynamics of Sargassum Growth

“The dynamics of sargassum on an Atlantic scale are highly complex. The Great Atlantic Sargassum Belt is influenced by discharges from rivers like the Amazon, making these waters warmer and less saline than those of the Sargasso Sea, where this algae originally formed,” Van Tussenbroek noted.

Scientific advancements have also enabled the development of algorithms to detect sargassum mats in open waters with greater precision, aiding in the design of more effective prevention and control strategies.

“What we do through science is essential to understanding and confronting this phenomenon, which grows stronger each year and endangers both coastal communities and marine ecosystems,” the researcher concluded.

Public concern over the issue has been amplified on social media, with residents and visitors expressing alarm over the environmental and economic impact on tourism-dependent regions like Quintana Roo and Playa del Carmen.

The situation underscores the urgent need for coordinated scientific, governmental, and community efforts to mitigate the escalating sargassum crisis in the Mexican Caribbean.