The Sargassum starts in Africa — but the Caribbean pays the price
📷 Cayman Compass
A landmark University of Miami study has finally answered the question haunting Caribbean coastlines since 2011 — tracing the region's catastrophic sargassum crisis not to the nearby Sargasso Sea, but to nutrient-rich waters off West Africa's Gulf of Guinea, forming up to two years before satellites detect the blooms moving westward, even as the Great Atlantic Sargassum Belt prepares to shatter its own 37.5-million-ton record in 2026.
For over a decade, scientists have debated where the Caribbean's sargassum nightmare actually begins. Now, a landmark study published in PNAS Nexus by researchers at the University of Miami Rosenstiel School has delivered a definitive answer — and it points thousands of miles from the beaches bearing the heaviest burden.
Using two independent analytical methods — Bayesian inversion modelling and transition path theory — the research team traced the origin of the first catastrophic bloom not to the Sargasso Sea, as long assumed, but to nutrient-rich coastal waters near the Gulf of Guinea off West Africa. Critically, that bloom was forming up to two years before satellites detected it moving westward toward Caribbean shores.
"Our results provide strong evidence that these blooms begin in the eastern tropical Atlantic, not in the Sargasso Sea as previously thought," said lead author Francisco Beron-Vera, a research professor in the Rosenstiel School's Department of Atmospheric Sciences.
Multiple lines of evidence support the finding: sargassum was already washing ashore in Ghana as early as 2009; the dominant varieties now choking Caribbean beaches differ biologically from Sargasso Sea species; and a 2009–2010 climate event resembling a 'Dakar Niña' — characterised by cooler sea surface temperatures and intensified nutrient upwelling off West Africa — is identified as the likely trigger. Saharan dust deposits and increased river runoff are cited as contributing factors that supercharged early bloom growth before ocean currents carried it westward.
Since that first major influx in 2011, the Great Atlantic Sargassum Belt has grown almost every year — with 2013 the sole exception — setting a biomass record of 37.5 million tons in 2025. Researchers at the University of South Florida's Satellite-based Sargassum Watch System now expect 2026 to surpass even that.
• Study published in PNAS Nexus by University of Miami Rosenstiel School researchers • Bloom origin traced to Gulf of Guinea coastal waters off West Africa — not the Sargasso Sea • Blooms forming up to two years before satellite detection in the western Atlantic • Two independent methods used: Bayesian inversion modelling and transition path theory • Sargassum reported washing ashore in Ghana as early as 2009 • A 2009–2010 'Dakar Niña-like' climate event identified as the likely trigger • Saharan dust and increased river runoff cited as contributing growth factors • Great Atlantic Sargassum Belt set a biomass record of 37.5 million tons in 2025 • 2026 forecast to surpass 2025 record, per USF Satellite-based Sargassum Watch System • Continuous annual blooms have occurred since 2011, with the exception of 2013
Previous record for the Great Atlantic Sargassum Belt, with 2026 projections expected to shatter this benchmark
Duration of catastrophic sargassum events affecting Caribbean coastlines since the geographic range expanded from the Sargasso Sea
Sargassum blooms form in West African waters up to 24 months before satellites detect them moving westward toward Caribbean shores
Duration of satellite data analyzed by Plymouth Marine Laboratory to characterize seasonal and annual sargassum biomass patterns in West Africa and Eastern Tropical Atlantic
The Great Atlantic Sargassum Belt now stretches from West African coasts across the Atlantic to the Caribbean and Gulf of Mexico, originating from the Gulf of Guinea
Sargassum biomass typically peaks in September in northern West African regions (Guinea to Gabon)
The origin of Caribbean sargassum crisis has been definitively traced to nutrient-rich waters off West Africa's Gulf of Guinea, not the nearby Sargasso Sea as previously believed, with blooms forming up to 2 years before detection
The Great Atlantic Sargassum Belt, which emerged in 2011, represents an unprecedented 15-year crisis driven by multiple compounding factors including climate change, nutrient pollution, and shifting ocean-atmosphere patterns rather than a single cause
Sargassum blooms follow predictable seasonal patterns in West Africa (September peaks in northern regions, July-August in southern regions), but seasons are beginning earlier and lasting longer, extending economic and environmental impacts
The 2026 sargassum inundation is projected to exceed the previous record of 37.5 million tons, indicating an escalating crisis affecting Caribbean tourism, fishing industries, and marine ecosystems
Economic hardship across Caribbean and West African communities results from sargassum clogging fishing gear, damaging boat engines, and degrading tourism infrastructure, with impacts compounded by the extended seasonal duration
The Caribbean's sargassum crisis has metastasised from seasonal inconvenience into a multi-sector emergency threatening tourism, fisheries, public health infrastructure, and freshwater security across more than 20 nations. A WHOI-URI study quantifies annual losses in Puerto Rico, the US Virgin Islands, and Florida's Atlantic coast at multi-million to potentially US billion-dollar levels. Hotel chains from Cancún to Martinique are now budgeting 'sargassum management' as a permanent operating expense, while small island governments — many ineligible for global climate funds due to their territorial status — are largely left to absorb reactive cleanup costs that experts say should be redirected toward prevention.
"Caricom countries recorded approximately US$102 million in economic losses from sargassum in 2022 alone — figures that exclude losses from the French Caribbean islands and do not account for annual beach-cleaning costs estimated at up to an additional US$210 million."
— Sylvie Gustave dit Duflo, Vice-President of the Guadeloupe Region / French Biodiversity Office, as reported by Centro de Periodismo Investigativo
Social Conversation: negative
Social media posts highlight the severe impact of record sargassum levels on Caribbean coastlines and tourism, linking it to climate change and nutrient runoff.
environmental impacttourism concernsclimate change
"@elonmusk 2 problems | 1 solution. Sargassum in the Caribbean is killing the biosphere, on the other hand, India, Ethiopia, several other countries are suffering from fertilizer shortages due to the conflict in Iran. Lets transform the sargassum into biofertilizer. Are you in?"
@charly_alba2045 · 12h ago · View on X
"MEXICO | Navy hauled 28K tons of sargassum from Caribbean beaches so far in 2026, racing to clear rotting algae before tourist season.
(Infobae)"
@LatamData · 💌 subscribe for full stories→ · 2d ago · 25 engagements · View on X
"Mexico is racing to stop an incoming swath of sargassum seaweed before it reaches its Caribbean coast. https://t.co/lSULpsogsR"
@the_inertia · Playa del Rey, CA · 4d ago · 1 engagements · View on X
"Record-high levels of sargassum inundated coastlines across the Atlantic, Caribbean, and Gulf in April, fueled by nutrient runoff and warmer waters. Scientists warn that 2026 could be a record year. #WetTribe #TidetotheOcean #Research #FridayFieldUpdate #Sargassum https://t.co/Xc"
@WetTribe · World Ocean · 4d ago · 38 engagements · View on X
Based on 6 posts from X · May 13, 2026
Viewpoint: The University of Miami team's dual-method approach — Bayesian inversion modelling and transition path theory — now allows researchers to trace bloom formation off the Gulf of Guinea up to two years before sargassum reaches Caribbean shores. NOAA has already upgraded its Sargassum Inundation Risk tool to daily, near-kilometre resolution updates. Lead author Francisco Beron-Vera argues the Gulf of Guinea origin finding fundamentally reframes where intervention efforts should focus — but scientists are careful to note that better prediction tools do not equal better outcomes unless governments act on the warnings.
Viewpoint: From the Jamaican fisher who cannot navigate his creek to the 4,000 Virgin Gorda residents who lost clean water, to the Guadeloupe schoolchildren sent home due to hydrogen sulfide levels — the human toll is relentless. Regional leaders argue that Caricom nations, which recorded US$102 million in losses in 2022 alone — excluding French Caribbean territories and up to US$210 million in beach-cleaning costs — deserve formal international compensation, not just scientific sympathy.
Viewpoint: Mexico has become the first country to officially classify sargassum as a fishery resource, opening coastal collection as a livelihood. FIU researchers have demonstrated 45 percent alginate extraction yields suitable for food manufacturing. Major hotel chains from Cancún to Martinique now budget permanent 'sargassum management' lines — money that could instead seed a regional valorisation industry if the regulatory and financing infrastructure is built out collectively.
The University of Miami's finding that Caribbean sargassum blooms originate off West Africa is important science — but the Caribbean cannot afford to wait for the next study. For 13 years, communities from Praslin Bay to Virgin Gorda have been breathing toxic air, losing livelihoods, and watching reefs suffocate while international coordination has stalled on funding gaps, geopolitics, and bureaucratic inertia. Better forecasting tools help, but they do not clean beaches, compensate fishers, or restore children's health.
The hard truth is that the nations most responsible for the nutrient pollution and climate warming driving these blooms — through river runoff, deforestation, and industrial agriculture — have contributed less than $7 million globally to sargassum-related projects over two decades. The Caribbean deserves more than photo opportunities from visiting dignitaries and draft management plans that gather dust.
Regional governments must press harder for formal international compensation mechanisms and push their larger partners to treat sargassum as the climate emergency it is. And within the region, the shift from reactive cleanup to proactive valorisation — learning from Mexico's fishery resource model — offers a realistic path to turning an existential burden into economic resilience.
Meanwhile, potential tourists to the islands will think twice, the more they hear about sargassum and the negative effect it can have on their holiday. This is the danger of depending on sea and sun. Only countries like Trinidad and Guyana, which have little dependence on tourism, can afford to be blaze about it.
Perhaps this common threat is something that can bring not just Caribbean nations, but all nations that border the Caribbean sea (and some that don't) together, to seek solutions.
If more thought can be given to sargassum and how it can be turned into an economic benefit, all will benefit.
Until then, the whole Caribbean lies victim, not to the Wide Sargasso Sea, but to the west coast of Africa, which also sends them their hurricanes.
Verified by Caribbean360's AI-powered fact-checking
El Niño may mean fewer 2026 Atlantic storms, but Caribbean experts warn one major hurricane can still be catastrophic. Here's what you need to know.
New research warns AMOC weakening threatens Caribbean hurricanes, rainfall & sea levels. Learn what this means for the region's future.
Caribbean nations forge a unified stance on fossil fuel phase-out, demanding debt relief and finance for small islands. Read the full regional strategy.
The U.S. Virgin Islands face weather risks every month—drought, floods, Saharan dust & more. Learn how to stay prepared all year long.