A perspective for the Caribbean Sea and Gulf of America* by the University of South Florida Optical Oceanography Lab – (bbarnes4@usf.edu, yuyuan@usf.edu, huc@usf.edu)

The map above shows the average Sargassum abundance for the month of November 2025, with warm colors representing higher abundance. The top color (red) indicates that 0.4% of the ocean surface is covered by Sargassum, meaning that Sargassum clumps and mats are scattered here and there in the location. The Sargassum abundance for each region is compared with historical values in the same month of 2011 – 2024 in the whisker box plot below, where horizontal bars in each vertical box indicate minimum, 25%, 50%, 75%, and maximal historical values, respectively.

As predicted last month, the total amount of Sargassum in each but the West Atlantic region continued to decline substantially in November, with Sargassum biomass more than halved. Total Sargassum amount for all regions combined decreased from 4.3M metric tons in October to 1.7M metric tons in November. Negligible amount of Sargassum was found in the Gulf of America and western Caribbean, and Sargassum “season” for all Caribbean and Gulf regions is over. Despite such sharp declines, total Sargassum amount in the eastern Caribbean and tropical Atlantic still exceeded 75% of their historical values in November.