For many years, experts have told us that sargassum is harmless to humans and swimming in a sea where the algae is present shouldn’t be an issue. Although that is still partially true, it is no longer recommended.
Let’s make things clear. Swimming on a beach with small patches of sargassum scattered across the waters poses little to no health risk.
The problem with sargassum today is that these small spots have become tons. This algae is not only present in the water but also on beaches, where it can sit for days in a phenomenon known as “invasion.“
The algae “is a good thing when it’s out offshore… Sargassum provides habitat for hundreds of species and invertebrates and even endangered sea turtles, supporting pelagic fisheries like mahi mahi and other fish that feed on prey items,” explains Brian LaPointe, a research professor at the Florida Atlantic University Harbor Branch Oceanographic Institute in Fort Pierce.
But sargassum is no longer secluded in the open sea. Since 2014, it has started to massively arrive at most Caribbean beaches, from the Lesser Antilles to the South of Florida.
Why you shouldn’t swim on beaches with sargassum
According to Rosa Elisa Rodríguez Martínez, member of the Academic Unit of Reef Systems of the Institute of Marine Sciences and Limnology of Quintana Roo, swimming in a sea covered with sargassum could be harmful to swimmers because it contains zinc, arsenic, lead and phosphorus.
On the other hand, the Center for Resource Management and Environmental Studies (CERMES) warned that prolonged contact with sargassum produces skin rashes and nausea.
When it decomposes, this algae causes “anoxia,” meaning the water loses oxygen. This produces an accumulation of poisonous sulfur gas, hence its unpleasant odor.
Jellyfish larvae present in big mats of sargassum can also cause itchy rashes and red spots on the skin.
“You can swim in the water if there’s sargassum and people do, but I have seen some reports of sea lice associated with sargassum in water with big mats of it floating around,” says LaPointe.
Here, the expert is referring to moderate quantities of sargasum, not what we are witnessing now on many beaches in the Caribbean.
Another aspect to be aware of is the stinging organisms living in big blobs of algae.
In addition to all of this, swimming with sargassum can also be unpleasant.
You will need to push it out of your route, but when it’s not possible, sargassum can feel like a loofah sponge rubbing up against your skin.
In fact, dolphins use it to scratch themselves, according to reports by the Wild Dolphin Project.
Therefore, it is best to look for a beach that is not heavily invaded by sargassum and to avoid entering the sea if there is a lot of algae.