Oceans & Turtles · Tortuguero, Limón

Sargassum Piles Up in Tortuguero in a Record Year for the Caribbean

In late February 2026, Costa Rica's environment ministry reported a fast-growing buildup of sargassum seaweed along the northern Caribbean coast, from the Nicaraguan border down through Tortuguero National Park. Officials said it may be one of the largest accumulations recently recorded there, and by June University of Costa Rica scientists were calling 2026 a record year.

By Pura-Verde.com Editors · Published October 30, 2026
Original report: The Tico Times: Sargassum Buildup Grows on Costa Rica Northern Caribbean Coast (2026-02-25)

Brown seaweed began piling up on Costa Rica's northern Caribbean beaches in late February 2026, and it kept coming. On Feb. 24, the Ministry of Environment and Energy (MINAE) said sargassum was building up steadily along the coast near Tortuguero National Park, in what preliminary records suggested could be one of the largest accumulations recently seen in the area. The Tico Times reported the alert on Feb. 25, a day after La Nación and El Observador carried the ministry's notice.

Where the seaweed showed up

According to MINAE and SINAC, the reports came in from three places: the Border Police post at Portillos, right at the Nicaraguan border; the village of Tortuguero; and stretches of the national park's shoreline. The ministry said the buildup started early that week and grew progressively.

The monitoring network also issued an early warning that sargassum could reach the southern Caribbean, including Manzanillo and Puerto Viejo, after the passage of a tropical wave.

What sargassum is

Sargassum is a floating brown alga that drifts in huge mats across the tropical Atlantic. The two species behind most Caribbean beachings, Sargassum natans and Sargassum fluitans, make up what scientists call the Great Atlantic Sargassum Belt. Large influxes into the Caribbean have been documented since 2011, hitting Mexico, Central America and many islands.

Out at sea, the mats are useful. They give many marine species shelter and food. The trouble starts when too much of it washes ashore and rots. La Nación noted that decaying sargassum gives off hydrogen sulfide, the rotten-egg gas, which can cause breathing problems in large amounts.

Why rangers aren't hauling it away

Visitors sometimes expect crews with rakes and trucks. In Tortuguero, that's not the plan. MINAE said the sheer volume rules out direct removal inside the protected area, and it described sargassum arrivals as a natural, dynamic process. Historically, the ministry said, the seaweed dries in the sun, breaks down, or gets carried back out by waves and currents.

Tortuguero is also not a typical beach town. It's a roadless stretch of coast reached by boat or small plane, and its 25 km nesting beach supports what the Tortuguero Conservation Area describes as the world's largest green turtle population. Heavy machinery on that sand would bring its own problems. Our guide to sea turtle conservation in Costa Rica explains how Tortuguero's nesting beach is protected.

Who's watching the coast

The Tortuguero Conservation Area (ACTo) has worked with the National University (UNA) and the Caribbean Sargassum Monitoring Network since 2019. Since 2023, its marine mammal surveys have also logged where offshore mats are, how big they are, how far they sit from shore and how wind and currents move them. MINAE said that data will help guide future management and research into possible uses. For the bigger picture, see our guide to marine conservation in Costa Rica.

What happened next: a record year

The February buildup turned out to be the start of a long season. In June, researchers Cindy Fernández and Mariana Viales of the University of Costa Rica's marine science center, CIMAR, told El Observador that 2026 arrivals were breaking records on the Caribbean coast. "This year we can say it broke records," Fernández said (translated from Spanish).

They said arrivals normally peak from March to May, but this year they began in February and were still going. The heaviest piles were in Tortuguero, Barra del Colorado and Isla Calero in the far north, while the south saw fewer arrivals, with occasional big pulses near Manzanillo. The scientists didn't attribute the record to any single cause, saying more data is needed, including on whether El Niño warming plays a role.

The regional picture matched. The University of South Florida's Optical Oceanography Lab, in its Feb. 28 sargassum outlook, reported record February amounts in every Atlantic and Caribbean region it tracks except the eastern Atlantic.

CIMAR is now building a community observer network from Gandoca to Barra del Colorado so residents can log when, where and how much sargassum lands, with the goal of a quarterly bulletin and, eventually, forecasts.

What it means if you're visiting the Caribbean coast

Sargassum isn't toxic to touch, the CIMAR researchers said, but they advise keeping away from large piles that are already rotting. Conditions change week to week and beach to beach, so ask your lodge or local guide what the shoreline looks like before you go. Tortuguero's canals, rainforest and guided turtle tours aren't affected the way a swimming beach is. Turtle watching there is only allowed with a certified guide, and you can find projects on our sea turtle map. For more Tortuguero news, read about the leatherbacks that arrived early this year and the rescue of a stranded baby manatee.

Frequently asked questions

Is there sargassum in Costa Rica?

Yes, on the Caribbean side. In 2026 it built up heavily from February onward, especially in Tortuguero, Barra del Colorado and Isla Calero, with smaller arrivals in the south near Manzanillo.

Is sargassum harmful to people?

The seaweed itself isn't toxic, according to UCR researchers. Large rotting piles release gases such as hydrogen sulfide, so it's best to keep your distance from them.

Why doesn't Costa Rica remove the sargassum in Tortuguero?

MINAE says the volume is too large for direct removal inside the protected area. It treats the arrivals as a natural process and lets sun, waves and currents break the seaweed down.

When is sargassum season in the Caribbean?

Arrivals usually peak from March to May, but UCR scientists said 2026 started in February and ran longer than normal.

Sources and original reporting

1. The Tico Times: Sargassum Buildup Grows on Costa Rica Northern Caribbean Coast (2026-02-25)
2. La Nación: Alerta por llegada masiva de sargazo a Tortuguero (2026-02-24)
3. El Observador: Minae reporta aumento de sargazo en el Caribe Norte y refuerza monitoreo en Tortuguero (2026-02-24)
4. El Observador: Sargazo rompe récords en el Caribe de Costa Rica: científicos advierten temporada más prolongada (2026-06-07)
5. CARICOOS / USF Optical Oceanography Lab: Outlook of Sargassum Blooms, February 28, 2026
6. Área de Conservación Tortuguero (official site)

We wrote this story from the published reports and official sources above. We didn't interview the people named unless the story says so.