Satellite imagery has revealed a massive 37.5 million-ton belt of brown seaweed stretching across the Atlantic Ocean from West Africa to the Gulf of Mexico, prompting urgent scientific concern. The phenomenon, dubbed the Great Sargassum Belt, consists of pelagic sargassum that has been spreading rapidly since 2010, far beyond its traditional habitat in the Sargasso Sea.

Researchers at Florida Atlantic University's Harbor Branch Oceanographic Institute analyzed four decades of satellite data showing the seaweed's explosive growth. The nitrogen content in the sargassum has increased by 55% between 1980 and 2020, with nitrogen-to-phosphorus ratios rising by 50%. This nutrient enrichment stems largely from agricultural runoff and wastewater discharge flowing into the Atlantic via the Amazon River.

The ecological impacts are severe. Massive sargassum blooms have washed ashore in unprecedented quantities, rotting and releasing toxic hydrogen sulfide gas while destroying coral reefs and depleting oxygen levels. In 1991, a Florida nuclear power plant was forced to shut down due to seaweed clogging its systems. Scientists warn that without reducing nutrient runoff, similar belts could form in other ocean regions, potentially accelerating climate change through greenhouse gas emissions.