Published on Wednesday, February 25, 2026
By the A.M. Costa Rica staff

The Ministry of Environment and Energy (MINAE) on Tuesday issued an alert over the arrival of a massive wave of Sargassum seaweed along the country’s northern Caribbean coast.

Authorities said the seaweed has intensified in recent days across the coastal stretch from Tortuguero National Park to the border with Nicaragua. Officials warned that this could be one of the largest recent accumulations recorded in the area.

Sargassum is a genus of brown macroalgae, classified as Phaeophyceae, found in temperate and tropical oceans worldwide. It typically inhabits shallow waters and coral reefs and is widely known for its free-floating, planktonic species.

 

The floating algae provide food, shelter and habitat for many marine species and play an important role in maintaining the health and biodiversity of open-ocean ecosystems.

However, authorities said the unusually large quantities now washing ashore could have negative consequences for the environment, public health and tourism,  particularly because of the strong odor released as the seaweed decomposes.

As it breaks down, Sargassum emits hydrogen sulfide, a colorless gas that smells like rotten eggs. In high concentrations, the gas can cause respiratory problems and affect residents living near the beach.

Specialists are advising the public not to consume the seaweed or use it as fertilizer. Scientific studies have identified the presence of accumulated heavy metals in the algae, making it unsuitable for consumption or handling, officials said.

Typically, Sargassum that reaches shore eventually decomposes, dries out under the sun and, over time, is carried back out to sea by waves and currents.

MINAE is the government agency responsible for environmental protection policy, natural resource management and the sustainable use of renewable energy in Costa Rica.

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What steps should Costa Rica take to prevent negative impacts on beach communities from the massive arrival of seaweed? We would like to know your thoughts on this story. Send your comments to news@amcostarica.com