What Is a Sargassum Bloom? What You Should Know About Giant Kelp

The 5,000-mile-long Great Sargassum Belt of the Atlantic held about 13 million tons of algae at the end of March

Photographer: Jonathan Alpeyrie/Bloomberg
April 05, 2023 | 01:48 PM

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Bloomberg — Sargassum blooms are hitting the coasts of Florida and the Gulf of Mexico by the ton, causing alarm among the population and the tourist industry. This is a natural phenomenon in which large quantities of sargassum algae accumulate on the surface of the sea and move toward the coast.

Sargassum Bloom Invades Florida Coast, Threatens Tourism

The Great Atlantic Sargasso Belt, which stretches 5,000 miles from the Gulf of Mexico to the west coast of Africa, contained about 13 million tons of algae at the end of March, according to researchers at the University of South Florida’s Optical Oceanography Laboratory, who have been conducting satellite monitoring, Sargassum Monitoring reports.

Water temperature, nutrients, wind and ocean currents are some of the factors determining the growth of this phenomenon, and climate change has led to an increase in the frequency and intensity of this type of bloom in recent years.

Environmental concerns include the reduction of oxygen in the water, the alteration of natural habitats and the disappearance of marine species. On an economic level, it hinders fishing and other marine activities, as well as scaring off tourists.


According to Visit Florida, the state’s tourism marketing corporation, visitors generate an annual revenue of more than $110 billion. In terms of federal taxes, tourism represents revenues of more than $11 billion.

The local algae season generally runs from May through October, with a peak in June and July, according to Tom Morgan, chief operating officer for Miami-Dade County Parks, Recreation and Open Space.

Speaking to Sargassum Monitoring, he said Miami-Dade County’s spending on algae cleanup increased from $2.8 million during the 2020 season to $3.9 million in 2022.

Now the county is asking the state Legislature for an additional $2 million to fund sargassum removal, which would bring this year’s total spending on seaweed cleanup to about $6 million.

What safety precautions should be taken?

  • Avoid direct contact with the kelp, as it may contain microorganisms and chemicals that can be harmful to health.
  • Do not inhale sargassum vapors if it begins to decompose, as it can produce toxic gases that can be dangerous if inhaled in large quantities.
  • Do not swim in areas with sargassum, as it can become entangled around the limbs and may contain dangerous marine creatures such as jellyfish and hermit crabs.
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