In 2025, a record breaking 40 million metric tons of Sargassum flowed through the tropical Atlantic, with especially severe accumulations along Puerto Rico’s coastline. On June 30, 2025, the Puerto Rican Governor signed an executive order declaring a state of emergency and expediting responses to Sargassum. In support of this effort, the National Centers for Coastal Ocean Science (NCCOS) Harmful Algal Bloom (HAB) Event Response Program is funding an expansion of response activities for the remainder of the 2025 sargassum season through 2026. This will supplement ongoing efforts by the Puerto Rico Department of Natural and Environmental Resources (DNER) to manage the current Sargassum emergency and better prepare for future influxes.
Large influxes of Sargassum are considered HABs when they inundate coastal waters and shorelines. Since 2011, the increased frequency and severity of Sargassum inundations have created challenges for coastal communities, wildlife managers, and commercial fisheries. Accumulated Sargassum can have considerable socioeconomic impacts: it deters tourism, damages critical infrastructure, deteriorates coastal habitats, and poses hazards to human health. Safe removal, disposal and proposed uses also pose significant challenges.
The NCCOS-supported event response is led by Mar Caribe Consulting LLC, with partners at the DNER and the Puerto Rico Coastal Zone Management Program, which will expand and complement Sargassum sampling efforts at six sites along Puerto Rico’s coastline. The results will help evaluate the likely abundance of Sargassum and water quality impacts during inundations and determine the levels of heavy metals within Sargassum biomass. The team will develop recommendations to improve future response efforts and inform guidance on safe handling and disposal and an approach to evaluate risks of alternate reuse strategies. This project also builds on another NCCOS-funded project by adding data on the volume of beached Sargassum in Puerto Rico to help validate improved Sargassum inundation predictions.
Local reports of Sargassum inundation in Puerto Rico should be directed to the Department of Natural and Environmental Resources. Learn more here.
The NCCOS HAB Event Response Program is a national program that provides immediate support to help state, tribal, and local officials manage events and advance the understanding of HABs as they occur. For more information, contact nccos.hab.event.response@noaa.gov.
NOAA is authorized to respond to harmful algal bloom events by the Harmful Algal Bloom and Hypoxia Research and Control Act (33 U.S.C. §§ 4001 et seq.).
