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Christopher Columbus had already noted the presence of a great deal of brown seaweed in the northeastern Atlantic Ocean. To such a point, the zone is known as the Sargasso Sea.

These micro-algae started moving toward the south, and now stretch across the Atlantic Ocean, from the Gulf of Mexico to the coasts of western Africa.

Since 2011, this seaweed has invaded the shores of the Caribbean islands and has been expanding at an unprecedented rate.

When drying, the alga emits hydrogen sulfide and ammonia, which can provoke severe headaches, nausea vomiting, respiratory difficulty, and vertigo.

The marine ecosystem also suffers a negative impact: the accumulation of the seaweed causes the death of certain species and destroys coral reefs. When it reaches a certain level of concentration, the sargassum also attacks metal, damaging motorcycles, cars, and computers.

This results in major environmental, economic, and health problems, which should concern all of the populations confronted with this phenomenon, as the invasion by this toxic seaweed seems to extend throughout a wider area than ever before.

This year, for example, the alga has been seen in Mexico and the Caribbean, but also in southwestern Florida.


25
millions of tons of sargassum seaweed
8850
km of sargassum
10
Multiply by 10 the volume of sargassum in 10 years

What are The Collectivities Doing?

Every time the seaweed washes ashore, the authorities are caught off guard, and have invested millions of euros in
technical equipment to deal with this threat.

In September 2018, the government announced a plan of action for the next few seasons comprising 12 million euros, with the goal of reducing the delay in cleaning up the seaweed to 48 hours after it washes ashore.

On the island of St Barthélemy, also impacted by this natural phenomenon, 2019 was the worst year for sargassum to date.
Close to 9,200 tons were collected (compared to 8,600 in 2018) for a total cost of 1,350,000€ (1,050,000€ in 2018).

This expense only covers the collection of the seaweed and transporting it to a storage site. But even if that reduces the most damaging impact to the beaches, the biggest challenge for everyone involved is the future of the algae: what to do
with it once it has been collected?