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Sargassum (Seaweed)

Download the Sargassum Factsheet

Florida Department of Health in St. Johns County Environmental Public Health Program

Beach with Brown Alga Sargassum on shoreline

Sargassum is a type of brown seaweed that is washing up on beaches in Florida. As it rots, it gives off a substance called hydrogen sulfide. Hydrogen sulfide has a very unpleasant odor, like rotten eggs. Although the seaweed itself cannot harm your health, tiny sea creatures that live in Sargassum can cause skin rashes and blisters.

Learn More About Sargassum

  • Sargassum provides an important habitat for migratory organisms including crabs, shrimp, sea turtles, and commercially caught fish, such as tuna and marlin.
  • Sargassum is common in the Sargasso Sea. The Sargasso Sea is a region of the North Atlantic Ocean. It is surrounded by four currents, but no land.
  • Currently, Florida has no regulatory guidelines for exposure to hydrogen sulfide at the beach.
  • Odors from most substances in outdoor air are not at levels that can harm your health. In enclosed spaces, gases may accumulate and can cause harm.
  • If workers are collecting and transporting Sargassum, they should wear protective clothing, such as gloves, boots, and gas filter half masks.

Sargassum Factsheet UPDATE: 03/17/2023

  • What is Sargassum?
  • Why is Sargassum a concern?
  • Why does Sargassum smell so bad?
  • How can hydrogen sulfide affect my health?
  • Does Sargassum cause skin rashes and blisters?
  • Will hydrogen sulfide from rotting Sargassum cause cancer or other long-term health effects?
  • Can I use Sargassum in cooking?
  • How can I protect myself and my family from exposure to Sargassum?

Sargassum is a brown seaweed that floats in the ocean and is washing up on Florida beaches in large amounts.

It provides an important habitat for migratory organisms that have adapted specifically to this floating algae including crab, shrimp, sea turtles, and commercially important fish species such as tuna and marlin.

 

  • The tiny sea creatures that live in Sargassum can irritate skin with direct contact.
  • Decomposing Sargassum causes an unpleasant smell.
  • People who live and work near the beach are concerned that Sargassum washing up along the beaches may harm their health.

When washed ashore, Sargassum will decompose (rot). Rotting Sargassum causes the production of hydrogen sulfide gas which smells like rotten eggs.

Hydrogen sulfide can irritate the eyes, nose, and throat. If you have asthma or other breathing illnesses, you will be more sensitive to hydrogen sulfide. You may have trouble breathing after you inhale it.

Sargassum does not sting or cause rashes. However, tiny organisms that live in Sargassum (like larvae of jellyfish) may irritate skin if they come in contact with it.

Hydrogen sulfide is not known to cause cancer in humans. If you are exposed to hydrogen sulfide for a long time in an enclosed space with little air flow (like some work exposures), it can affect your health. However, hydrogen sulfide levels in an area like the beach, where large amounts of air flow can dilute levels, is not expected to harm health.

You should not use Sargassum in cooking because it may contain large amounts of heavy metals like arsenic and cadmium.

  • Always supervise children at the beach.
  • Avoid touching or swimming near seaweed to avoid stinging by organisms that live in it.
  • Use gloves if you must handle seaweed.
  • Stay away from the beach if you experience irritation or breathing problems from hydrogen sulfide—at least until symptoms go away.
  • Close windows and doors if you live near the beach.
  • Avoid or limit your time on the beach if you have asthma or other respiratory problems.

If you have questions or comments about Brown Alga (Sargassum), contact:

Write to:

Division of Disease Control and Health Protection
Bureau of Environmental Health, Public Health Toxicology
Florida Department Health
4052 Bald Cypress Way, Bin # A-08
Tallahassee, FL 32399

Call:

Public Health Toxicology Toll free at: 877-798-2772