An enormous bloom of seaweed in the Atlantic

Since 2011, the central Atlantic Ocean has seen a massive seaweed bloom nearly every spring and summer. Patches of drifting earthy colored ocean growth — known as Sargassum — have extended from the west shore of Africa to the Bay of Mexico in what is known as the "Incomparable Atlantic Sargassum Belt." In Walk 2023, researchers found that how much Sargassum drifting in the belt was the biggest of any Walk on record.

The Sargassum density for March 2023 in the central Atlantic Ocean, which includes the Caribbean Sea and Gulf of Mexico, is depicted on the map above. In terms of the percentage of each pixel that is covered in seaweed, the red and orange regions indicate the locations with the highest densities of Sargassum. Using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA's Terra and Aqua satellites, researchers at the USF College of Marine Science developed the map's data.

In March, the Sargassum belt produced approximately 13 million tons, a record for this time of year, according to USF researchers. Brian Barnes, a marine scientist at the Optical Oceanography Laboratory at USF, stated, "Record high Sargassum abundance is primarily in the central East Atlantic so far this year." However, its abundance remains high in other parts of the Atlantic and Caribbean, ranking in the 75th percentile of measurements taken between 2011 and 2022.