Florida scientists believe they have discovered a “tipping point” in atmospheric conditions in the Atlantic Ocean that has led to the inundation of toxic seaweed clumps on Caribbean beaches during recent summers. Previous theories for the “Great Atlantic Sargassum Belt” have included a surplus of nutrients in the water, such as nitrogen and phosphorus. However, scientists at the University of South Florida recognized a seasonal phenomenon known as vertical mixing as the primary source of nutrients, with atmospheric pressure changes over the Atlantic as the “tipping point.” The changing atmospheric conditions have been pushing more sargassum into the warmer waters of the tropics, where it grows into massive blooms and ends up on beaches. The rotting sargassum releases hydrogen sulfide, which can provoke asthma and other respiratory issues. In 2023, scientists at Florida Atlantic University warned of a “perfect pathogen storm” with implications for both marine life and public health, having found high levels of the flesh-eating Vibrio bacteria lurking in the decomposing vegetation. The bacteria can create an additional health risk for tourists and be found to stick to plastic debris in ocean pollution. The USF research was published in Nature Communications.

Source: https://www.theguardian.com/us-news/2025/mar/22/cause-toxic-seaweed-florida-sargassum