The Problem

Sargassum is suffocating the Caribbean, releasing millions of tons of climate-heating gases along the way. Since 2011, the Caribbean has experienced a surge in Sargassum Inundation Events (SIEs). Massive blooms of pelagic seaweed washing ashore in volumes we’ve never seen before.

What might seem like a coastal nuisance for beach goers is actually a climate, ecological, health, and economic crisis. When sargassum washes up on land, it decays, releasing carbon dioxide (CO₂) and methane (CH₄)—both potent greenhouse gases.

The emissions numbers from sargassum alone are staggering: 6.75 million metric tons CO₂-equivalent yearly from just the Caribbean.

That’s like:

810,000 cars on the road for a year
Nearly 3 million barrels of oil burned
Wiping out the carbon-absorbing power of 7.6 million acres of U.S. forest
Almost 3 billion kWh of electricity consumed

Even just the top 9 impacted islands account for 2.2 million metric tons CO₂-equivalent. That’s equal to:

263,000 vehicles’ worth of emissions
944,000 barrels of oil
2.5 million of acres of the U.S. forest’s carbon-absorbing power
3 billion kWh of electricity consumed

A 1,000-ton sargassum bloom can emit 302,000 kg of CO₂-equivalent from methane alone. And that’s just methane. Hydrogen sulfide and other toxins only add to the problem.

Environmental & Ecological Harm

Smothers Life: Sargassum blankets beaches, reefs, and seagrass beds. It blocks sunlight and choking off oxygen, disrupting photosynthesis, killing marine life, and degrading nursery habitats. As a result, the ocean is seeing devastating biodiversity loss, including: fish, invertebrates, and coral nurseries are suffering devastating losses. And marine mammals, turtles, and other wildlife are at risk of entanglement or suffocation.
Destabilizing Ecosystems: Sargassum accumulates nutrients and heavy metals, including arsenic. As the seaweed rots, these toxins can be released into coastal ecosystems, contaminating marine food webs and human consumers.
Blue Reversal: While floating Sargassum acts as a blue carbon sink, absorbing atmospheric CO₂, decomposition onshore reverses this benefit. As Sargassum decays, it releases stored carbon back into the atmosphere as CO₂ and methane (CH₄), both potent greenhouse gases.

Public Health Crisis

When sargassum breaks down, it emits:

Hydrogen sulfide (H₂S) and ammonia, triggering nausea, headaches, and breathing issues.
Long-term exposure is linked to pregnancy complications, hypertension, and chronic illness.
Heavy metals like arsenic can contaminate water and soil, entering the food chain at all levels.

Economic Fallout

Tourism tanks: Foul smells, unswimmable beaches, and canceled vacations devastate the local economy.
Fishing suffers: Damaged equipment, smaller catches, and high cleanup costs.
Communities pay: Governments and residents are footing the bill for nonstop beach cleanup with no long-term relief in sight.

Solutions Are Emerging, but Time Is Running Out

Policy and Coordination: National and regional agencies, including the U.S. National Oceanic and Atmospheric Administration and Food and Agriculture Organization, emphasize the need for coordinated management, improved forecasting, and regulatory frameworks to address Sargassum influxes.
Repurposing and Valorization: Research and pilot projects are exploring the conversion of Sargassum into biofuels, fertilizers, and bioproducts, aiming to reduce environmental impacts and create economic opportunities.
Deep-Ocean Sinking: Artificial burial or deep-ocean deposition of Sargassum is under consideration as a carbon sequestration strategy, but this ecologically-questionable solution requires further study to assess long-term impacts and feasibility.

The Sargassum Problem