In June 2026, the Great Atlantic Sargassum Belt reached its second-highest recorded extent, driven by record-setting blooms in the Caribbean Sea and Gulf of Mexico. While this seaweed supports ocean life offshore, excessive amounts near coastlines create environmental and economic concerns.
- Sargassum hits all-time highs in Caribbean Sea and Gulf of Mexico
- Second-largest overall bloom measured by NASA's PACE satellite
- Satellite tracking helps predict coastal impacts and guide preparation
What happened
In June 2026, satellite observations recorded near-peak levels of the Great Atlantic Sargassum Belt, with the Caribbean Sea and Gulf of Mexico reaching historic highs. The western and eastern Caribbean saw 3.6 and 9 million metric tons of Sargassum, respectively, while the Gulf recorded an unprecedented 5 million metric tons, nearly doubling its previous record from 2025. These measurements place 2026 as the second-largest Sargassum bloom year on record.
This giant floating algae formation stretches from the waters off West Africa across the tropical Atlantic toward the Caribbean and Gulf. Satellite instruments on NASA’s PACE satellite, supported by earlier observations from Terra, Aqua, and NOAA-20 satellites, detect how much ocean surface area is covered by the brown seaweed by measuring its unique light reflectance characteristics.
Why it feels good
Sargassum plays an important role in marine ecosystems. In open waters, it provides a habitat for turtles, fish, invertebrates, and birds, acting as a floating nursery and refuge. Its photosynthesis contributes valuable oxygen to ocean waters, supporting overall marine health.
Scientists use satellite monitoring to give communities advanced notice about the extent and movement of Sargassum mats. This tracking enables better coastal preparation for the arrival of seaweed, helping local economies and ecosystems adapt and mitigate potential negative impacts.
What to enjoy or watch next
The ongoing monitoring of Sargassum via satellites like NASA’s PACE affords valuable insights into how ocean currents and climate factors shape its spread. While Florida’s west coast has been spared significant seaweed influx this summer, large amounts continue to affect the Florida Keys and east coast, alongside more severe accumulation in the Caribbean.
Research teams at the University of South Florida and NOAA continue to refine their detection techniques, providing increasingly detailed maps and forecasts. Watching how this giant seaweed belt evolves will be key for marine scientists, coastal communities, and policymakers aiming to balance ecological benefits with coastal challenges in the years ahead.