General Sargassum Information

Sargassum seaweed is a free-floating brown seaweed that originates in the Sargasso Sea and the equatorial Atlantic. Since 2011, a weather pattern shift has caused enormous quantities to wash into the Caribbean, including Belize’s coastline, each year. Because Belize sits along the Caribbean’s eastern-facing coastline, some beaches catch the seasonal drift while inland Belize remains completely unaffected.

• Sargassum blooms originate in the Atlantic’s Great Atlantic Sargassum Belt (GASB), which can stretch over 8,000 kilometres.
• It arrives in Belize through prevailing easterly winds and the North Atlantic Gyre current, with the heaviest impacts typically between June and October.
• When it accumulates on beaches, it decomposes and releases hydrogen sulfide and ammonia gases, creating a strong odor. Underwater, it remains harmless.
• The barrier reef provides protection for many inner-reef and lagoon areas. Mainland beaches facing east generally receive the most exposure, while leeward cayes and lagoon-side swimming areas are often clearer.
• Sargassum levels vary significantly each year. Checking current-season forecasts is recommended before planning beach-focused activities.

Historically, most Sargassum accumulated in the Sargasso Sea in the western North Atlantic, with smaller amounts found in the Gulf of Mexico and Caribbean Sea. In 2011, the geographic range expanded, and large quantities began moving west into the Caribbean Sea, Gulf of Mexico, and tropical Atlantic.

These floating mats have since reached coastal areas throughout the Caribbean, Florida, Puerto Rico, the U.S. Virgin Islands, and parts of Western Africa.

The main Sargassum season in Belize generally runs from March through October, with peak activity typically occurring between June and August. Conditions can change from week to week depending on ocean currents, wind patterns, and weather conditions.

For the most accurate information, travelers should monitor live Sargassum maps and local updates closer to their travel dates.

Sargassum exposure varies greatly depending on beach orientation, prevailing winds, and protection from Belize’s barrier reef.

• Ambergris Caye (San Pedro): Eastern beaches may experience moderate exposure, while western lagoon-side areas such as Secret Beach are generally clearer. Reef snorkeling remains unaffected.
• Caye Caulker: The Split and channel areas typically remain clear, while some eastern beaches may receive seasonal accumulation. Snorkeling sites like Hol Chan remain unaffected.
• Placencia: Southern beaches and the village coastline may experience more exposure. The Placencia Lagoon side is generally clearer, and offshore cayes are unaffected.
• Hopkins: Facing east-southeast, Hopkins can experience heavier accumulations during peak months. Pool access and inland activities provide excellent alternatives during heavy weeks.
• Cayo / San Ignacio: Completely unaffected. Rivers, waterfalls, caves, and jungle adventures provide a perfect alternative to coastal activities.
• Turneffe Atoll and Outer Cayes: Offshore reef areas are generally unaffected, as Sargassum typically concentrates closer to shore.

Since 2011, large Sargassum accumulations have occurred annually throughout the Caribbean Sea, Gulf of Mexico, and tropical Atlantic, although the amount varies from year to year.

Sargassum does not form a continuous blanket across the ocean. Instead, it floats in patches ranging from a few centimeters to hundreds of meters wide. Some patches eventually reach coastal areas, affecting beaches, ports, and water intake systems.

Satellite monitoring allows researchers to estimate Sargassum coverage and track changes in volume and distribution across affected regions.

In the open ocean, Sargassum provides an important habitat for fish, sea turtles, and many other marine organisms. However, when large amounts reach shore, it can create challenges for coastal environments.

Accumulated Sargassum can smother coral reefs, seagrass beds, and beaches. As it decomposes, it produces hydrogen sulfide gas, creates odors, attracts insects, and may impact navigation, tourism activities, water systems, and coastal ecosystems.