It’s that time of year when we’re seeing an influx of that brown seaweed along the beaches.
What is it? Where does it come from? Is it dangerous?
It’s called Sargassum.
Sargassum is a genus of brown (class Phaeophyceae) macroalgae (seaweed).Wikipedia
Sargassum is a term coined by Portuguese sailors—which has even been attributed to Christopher Columbus during his 1492 expedition.
Sargassum is home to over 100 species of sea life and provides an important habitat for migratory organisms that have adapted specifically to these floating algae including crab, shrimp, sea turtles, and commercially important fish species such as mahi mahi, jacks, tuna, and marlin.
Where does it come from?
It originates in the Sargasso Sea (and to be totally honest we’d never heard of the sargasso sea until researching the topic):
Each year, the summertime trade winds blow the seaweed onto the beach from offshore.
Is Sargassum dangerous to humans?
Sargassum does not sting or cause rashes. However, tiny organisms that live in the Sargassum (like larvae of jellyfish) may irritate the skin if they come in contact with it.
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.
However, hydrogen sulfide levels in an area like the beach, where large amounts of airflow can dilute levels, are not expected to harm health.
Coming in direct contact with the seaweed can make you itchy but other than that it’s not really harmful and just a part of many coastal ecosystems in the northern Atlantic.
One use of the seaweed once it’s washed ashore is to use it to write notes in the sand, a trend (to the best of our knowledge) we started as a guerilla marketing tactic all the way back in 2006: