Sargassum is a brown seaweed with berrylike air bladders, typically forming large floating masses. This brown seaweed provides a crucial habitat for many marine species, including endangered sea turtles which, upon hatching on our beaches, make their way out to the Sargassum to spend their juvenile years feeding and growing amongst the seaweed mats. Sargassum comes from the largest bloom of macroalgae in the world, the Great Atlantic Sargassum Belt (GASB), which blankets the surface of the tropical Atlantic Ocean from the west coast of Africa to the Gulf of Mexico.

Sargassum season runs from March through October, and Sargassum now aggregates almost every year, starting January/February in a massive belt north of the Equator. During the late winter and early spring months, Sargassum moves northward due to seasonal winds and currents. Later, in late spring and summer, this Sargassum belt may stretch across large portions of the Atlantic Ocean and drift into the Caribbean Sea and Gulf of Mexico via the North Equatorial and Caribbean current systems.

Sargassum has flourished in recent years due to the combination of increased nutrient runoff from the Amazon River, upwelling off the western coast of Africa, and changing water temperatures. The greatest accumulations of Sargassum on our beaches often happen during high tide, which we experience twice a day. City of Boca Raton’s Recreation Services crews generally clean Sargassum early in the morning, prior to when most beachgoers have arrived at the beach. Unfortunately, when the second tide arrives in the afternoon, depending on the winds, it often brings another wave of Sargassum to the shoreline.

According to the Florida Department of Health (DOH), the Sargassum itself is not harmful to the skin, but tiny sea creatures that live in Sargassum can cause skin rashes and blisters. As Sargassum decomposes, it also gives off a substance called hydrogen sulfide. Hydrogen sulfide has a very unpleasant odor that resembles rotten eggs, and this can irritate the eyes, nose, and throat. If you have asthma or other breathing illnesses, you may be more sensitive to these symptoms. However, the levels of hydrogen sulfide in an area like the beach, with large amounts of airflow, are not expected to be harmful.

To protect yourself and your family from exposure to Sargassum, DOH advises the following:

• 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.

We are monitoring evolving literature on the relationship between Sargassum and Vibrio vulnificus bacteria, including a recent study that suggests that this bacteria can “stick” to microplastics which increasingly live in our oceans and can become lodged in patches of Sargassum. According to the Florida Department of Health, people can get infected with Vibrio vulnificus when they eat raw shellfish, particularly oysters. The bacterium is frequently isolated from oysters and other shellfish in warm coastal waters during the summer months. Since it is naturally found in warm marine waters, people with open wounds can be exposed to Vibrio vulnificus through direct contact with seawater.

To reduce your chance of getting a Vibrio wound infection, DOH recommends the following:

• Water and wounds do not mix. Do not enter the water if you have fresh cuts or scrapes.
• Individuals who are immunocompromised, e.g. chronic liver disease, kidney disease, or weakened immune system, should wear proper foot protection to prevent cuts and injury caused by rocks and shells on the beach.

Water quality can be impacted by the decomposition of Sargassum. The Florida Department of Health (FDOH) monitors bacteria levels at the County's beaches through their Healthy Beaches program through the collection of water samples at various locations.