Pictured Above: In 2023, WHOI scientists aboard the NOAA ship Ronald H. Brown in the tropical Atlantic took advantage of the ship’s long-planned path through the Great Atlantic Sargassum Belt to take some of the first samples from a massive, ongoing bloom. (Photo by Ellen Park ©Woods Hole Oceanographic Institution)
Sargassum, a genus of large brown seaweed (a type of algae) that floats in island-like masses and never attaches to the seafloor. is expected to have a record bloom year in 2026, according to researchers at the University of South Florida’s Satellite-based Sargassum Watch System (SaWS), which uses satellite data and numerical models to detect and track pelagic Sargassum in near-real time.
The SaWS March 2026 Bulletin Outlook forecasts that most monitored regions will continue to increase in April 2026, with 2026 set to be another major Sargassum year (i.e., one in which the Sargassum amount exceeds 75% of the historical values), and likely to be a record year by summer 2026.
Sargassum beaching events in both the Western Caribbean and the Eastern Caribbean will continue, while the Florida Keys and southeast coast of Florida will likely see moderate beaching events in the coming month as Sargassum in the Gulf of America will continue to be transported to these locations.
What is Sargassum? USF Explains
The University of South Florida’s Optical Oceanography Laboratory explains that Pelagic Sargassum seaweed is a brown macroalgae floating on the ocean surface. Comprised primarily of two species, S. natans and S. fluitans, it is abundant in the Intra-Americas Sea (IAS), the Atlantic, and along the coasts of British Isles and mainland Europe.
In the ocean it serves as an important habitat for many marine animals as it provides food, shade, and shelter (from predators) to fish, shrimp, crabs, and turtles. Sargassum may serve as fertilizers for sand dunes and thus protects shoreline stability. It is also a marine resource for other uses such as biomass for food, fuel, and as a possible source of pharmaceutical materials.
However, excessive amounts of Sargassum on beaches in populated areas can cause a lot of problems and they must be physically removed. Sargassum decomposition on beaches smells bad, attracts insects, and causes many environmental problems (e.g., smothering turtle nesting sites, sea turtle mortality, fish kills) and economic problems (e.g., diminished tourism).
The beaches along the Texas coast have experienced Sargassum inundation events annually, and since 2001 beaching events have also occurred on many Caribbean shores in nearly every spring and summer. Sargassum beaching events have also been reported in western Africa and northern Brazil.
Monitoring Sargassum distribution and abundance in the ocean in a timely fashion is of great importance for studying ocean ecology, helping fishery management, and forecasting Sargassum beaching events.
The SaWS is meant to provide such a function through producing and sharing customized satellite imagery in near real-time in a user-friendly way.
New Woods Hole study quantifies sargassum’s multi-million dollar impact to U.S. coastal economies
A study published in January 2026 and led by researchers at the Woods Hole Oceanographic Institution (WHOI) and the University of Rhode Island (URI) provides the most comprehensive assessment to date of the economic damage caused by recurring sargassum seaweed inundation events across U.S. coastal regions. The research quantifies multi-million, and in some areas potentially billion-dollar, annual losses affecting Puerto Rico, the U.S. Virgin Islands (USVI), and Florida’s Atlantic coast.
Funded by NOAA’s National Centers for Coastal Ocean Science (NCCOS) Competitive Research Program in 2020 the study addresses a critical knowledge gap. “While the ecological and public health impacts of sargassum inundation events (SIEs) have been widely documented,” said Tracey Dalton, a professor of Marine Affairs at URI , the lead principal investigator of the URI-WHOI collaborative project on assessing societal impacts of harmful macroalgae blooms in the Caribbean, “their direct and indirect economic costs to governments, coastal communities, and private industries had not previously been quantified.”
“Understanding the economic scale of sargassum impacts is essential for informed decision-making,” said Di Jin, a senior scientist at the Marine Policy Center at WHOI, and the lead author on the study. “Our findings provide resource managers with evidence-based estimates that can guide investments in forecasting, response, and long-term mitigation strategies.”
WHOI led the study’s economic modeling and analysis, examining impacts across three sectors central to coastal economies: tourism, recreation, and fisheries. These sectors are particularly vulnerable to sargassum accumulation, which can foul beaches, disrupt fishing operations, damage coastal infrastructure, and deter visitors.
The research integrates economic modeling, satellite observations, tourism, and fisheries data, and long-term sargassum monitoring to translate environmental disruption into actionable economic evidence.
“NCCOS’ partnership with WHOI underscores the value of applied science in delivering actionable information for coastal managers, from guiding investments in effective Sargassum response and cleanup strategies to helping communities protect livelihoods, tourism, and long-term economic resilience” said NCCOS director Sean Corson.
To quantify these impacts, the research team integrated multiple data sources and analytical approaches, including national income and employment statistics for marine and coastal industries, NOAA’s Sargassum Inundation Reports and field observations from the Sargassum Watch database to estimate the frequency and duration of inundation events, estimated tourism losses due to hotel cancellations and reduced visitor spending, and estimates on declines in commercial and recreational fishing landings. This multi-sector approach allowed researchers to develop a robust, region-specific picture of the growing financial burden imposed by increasingly frequent and prolonged sargassum seasons.
The study shows that sargassum seasons are beginning earlier and lasting longer across the Caribbean and western Atlantic, increasing the frequency and severity of coastal impacts. Puerto Rico, the U.S. Virgin Islands, and southeast Florida face the highest risk of severe sargassum inundation, with annual economic losses already reaching multi-million-dollar levels in Puerto Rico and the USVI and potentially rising to billion-dollar impacts along Florida’s Atlantic coast.
Despite these growing challenges, existing sargassum forecasting tools are performing well and can play a critical role in supporting improved planning, preparedness, and response efforts.
“These results highlight the urgency of sustained investment in sargassum monitoring, forecasting, and cleanup infrastructure,” Dalton notes. “Without proactive management, the economic consequences for coastal communities will continue to escalate.”
The study builds on decades of WHOI expertise in large-scale ocean circulation, biogeochemistry, and ecosystem change. Today’s unprecedented sargassum events are not isolated phenomena, but symptoms of broader shifts in the Atlantic Ocean system.
Massive sargassum blooms—now forming what researchers refer to as the “Great Atlantic Sargassum Belt”—stretch thousands of miles from West Africa to the Caribbean, Gulf of Mexico, and U.S. Atlantic coastline. The Great Atlantic Sargassum belt appears to have been initiated by unusual wind and circulation patterns in the winter of 2009-2010, subsequently fueled by high nutrient availability in the tropical Atlantic.
“As the Atlantic continues to change, we’re seeing cascading effects that directly connect offshore ocean processes to coastal economic vulnerability,” said Jin. “This study links those large-scale environmental drivers to real-world economic consequences.”
About Woods Hole Oceanographic Institution
Woods Hole Oceanographic Institution (WHOI) is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its mission is to understand the ocean and its interactions with the Earth as a whole, and to communicate an understanding of the ocean’s role in the changing global environment.
WHOI’s pioneering discoveries stem from an ideal combination of science and engineering—one that has made it one of the most trusted and technically advanced leaders in fundamental and applied ocean research and exploration anywhere.
WHOI is known for its multidisciplinary approach, superior ship operations, and unparalleled deep-sea robotics capabilities. We play a leading role in ocean observation and operate the most extensive suite of ocean data-gathering platforms in the world.
Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide—both above and below the waves—pushing the boundaries of knowledge to inform people and policies for a healthier planet.
Learn more at whoi.edu.
