Record-Breaking Sargassum Bloom Advances Toward the Mexican Caribbean

Mexican Caribbean, Mexico — The Atlantic Ocean is currently carrying what scientists describe as the largest sargassum bloom ever recorded, with more than 38 million metric tons of floating seaweed forming a massive transoceanic belt stretching from West Africa to the Caribbean and Gulf of Mexico.

According to data from the University of South Florida’s Optical Oceanography Lab — which has monitored the phenomenon via satellite since 2011 — this year’s bloom surpasses previous records set in 2018 and 2022. Researchers confirmed that the Great Atlantic Sargassum Belt reached unprecedented density during peak monitoring this season.

What Is the Great Atlantic Sargassum Belt?

The Great Atlantic Sargassum Belt is a vast floating mass of brown macroalgae (primarily Sargassum natans and Sargassum fluitans) that forms in the tropical Atlantic. Unlike the Sargasso Sea, where sargassum naturally accumulates offshore, this belt drifts westward with ocean currents toward the Caribbean and the Gulf of Mexico.

Since 2011, blooms have grown in both frequency and intensity. Scientists believe this is linked to a combination of warming ocean temperatures, altered wind and current patterns, and increased nutrient runoff from major river systems such as the Amazon, Orinoco, and Mississippi.

Why This Year Is Different

The 38-million-ton estimate represents the largest biomass recorded since satellite tracking began. Researchers note that warmer-than-average Atlantic surface temperatures and high nutrient input have created ideal growth conditions.

While sargassum is a natural part of marine ecosystems offshore — providing habitat for fish, turtles, and invertebrates — problems arise when massive quantities reach coastal zones.

Impact on the Mexican Caribbean

In the Mexican Caribbean — including Cancún, Puerto Morelos, Playa del Carmen, Cozumel, Tulum, and Mahahual — sargassum season typically peaks between May and September. This year’s record bloom suggests continued heavy arrivals through the summer months.

When sargassum piles up on beaches and decomposes, it releases hydrogen sulfide gas, producing a strong odor similar to rotten eggs. In high concentrations, this gas can cause eye irritation, headaches, and respiratory discomfort.

Environmental impacts include:

• Smothering of coral reefs and seagrass beds
• Reduction of oxygen levels in nearshore waters
• Disruption of sea turtle nesting sites
• Impacts to coastal fisheries

Municipal governments along the Riviera Maya have already activated containment strategies, including offshore sargassum barriers, specialized collection vessels, and daily beach cleanups. The Mexican Navy continues to deploy sargassum-collection ships as part of a coordinated response.

Economic and Tourism Effects

Tourism-dependent destinations across the Caribbean are closely monitoring the bloom. Beach conditions fluctuate daily depending on currents and winds, meaning some stretches may be heavily impacted while others remain relatively clear.

Florida and several Caribbean islands have also reported above-average accumulations. In some locations, sargassum has disrupted recreational boating and nearshore fishing.

What Is Causing the Increase?

Researchers emphasize there is no single cause. Contributing factors include:

• Ocean warming linked to climate change
• Changes in Atlantic wind circulation
• Increased nutrient runoff from agriculture and deforestation
• Saharan dust transporting iron and phosphorus
• Large-scale climate oscillations

The phenomenon is widely viewed as a visible indicator of broader ocean system changes.

A Long-Term Challenge

Scientists do not expect the Great Atlantic Sargassum Belt to disappear in the near future. Instead, seasonal blooms may remain a recurring feature of Caribbean coastal life.

For the Mexican Caribbean, the focus remains on mitigation, adaptation, and ongoing research. While the current bloom is historic in size, experts note that not all 38 million tons will reach Mexico’s shores. Ocean currents disperse and redirect much of the biomass.

Even so, 2026 is shaping up to be another challenging sargassum season for the region.