Sargassum Tracker

USF OOL Long Term Outlook

May 31, 2025
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As predicted last month, while the spatial distribution patterns of Sargassum remained stable, Sargassum amount in each region increased in May considerably. In every but the Gulf of Mexico region, Sargassum amount exceeded its historical record. In particular, total Sargassum amount from all regions combined further increased from 31M tons in April to 37.5M tons in May, making a new record. Most of these increases are due to both local growth and physical transport. Corresponding to these increases, significant Sargassum inundation events may have occurred around most Caribbean nations and islands, including the Mexican Caribbean coast. Small to moderate amount of Sargassum may have reached some of the Florida beaches along the Florida Keys and southeast coast of Florida. Small amount of Sargassum was also observed in the Mississippi delta and along Texas coast.

Looking ahead: As in most previous years, June is expected to see continued increases in sargassum in most regions. More sargassum is projected to be transported to the western Caribbean Sea and then to the Gulf via the Yucatan. Sargassum flooding will continue to occur in most Caribbean countries and islands, as well as along the southeastern coast of Florida. However, while 2025 is a record-breaking year for sargassum, whether a beach or small region receives a record-breaking sargassum flood depends not only on the amount of sargassum offshore, but also on difficult-to-predict local factors such as winds and ocean currents.

SARGASSUM ABUNDANCE INTENSITY

Details

Since 2011, large amounts of Sargassum seaweed appeared in the Caribbean Sea every summer except 2013, creating many environmental, ecological and economic problems in many regions. The seaweed originated from the tropical Atlantic, and is believed to be a result of climate variability and other natural and unnatural processes. Based on satellite observations and statistics of historical events, in early February 2018 the Optical Oceanography Lab developed the first 1-page Sargassum outlook bulletin for the Caribbean Sea. Since then, the bulletins have been generated and distributed to subscribers by the last day of the month. In April 2025, the total Sargassum amount sets a new record that exceeds the all-time high in June 2022, while the exact reasons remain to be investigated. Further details can be found in the attached bulletin.

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Disclaimer

The information bulletin is meant to provide a general outlook of current bloom condition and future bloom probability for the Caribbean Sea. By no means should it be used for commercial purpose, or used for predicting bloom conditions for a specific location or beach. The authors of this bulletin, as well as Caricoos, USF and NASA, take no responsibility for improper use or interpretation of the bulletin. Any use of the image, data, or graph from this bulletin page in reports or publications should obtain permission from the USF OOL group.