Invasion of the Sargassum Weed

By Peter Nielsen

October 5, 2015

We were a couple of hundred miles out of Bermuda on the 39ft cutter Lunacy, en route to St. Martin, when the small floating islands of brown seaweed that dotted the ocean started to become a nuisance. Clumps of it wrapped around the keel and rudder, and skipper Charlie Doane grew increasingly annoyed at the amount of time he spent with a boathook trying to clear the Aries vane gear’s paddle. We even had to stop the boat a few times to let the weed fall off the foils.

Doane struck similar problems a few months later when sailing with ARC founder Jimmy Cornell from Ft. Lauderdale to Panama, and in between those dates the entire Caribbean island chain had been inundated—if that’s the word—with the errant Sargassum weed, for that’s what it is, the same stuff that’s been driving mariners nuts for centuries in the Sargasso Sea. Indeed, there have been reports of the unsightly brown weed as far north as New York.

The Sargasso Sea lies mainly south and east of Bermuda in the Atlantic Gyre, a 2 million-square mile ellipse of water bordered by slowly rotating ocean currents. The sheer amount of weed, combined with the prevailing calms, gave rise to torrid tales of ships becoming entangled in the grip of these massive rafts of algae.

So why is the Sargasso Sea apparently heading west? Sargassum weed has always been present in U.S. coastal waters—Pacific as well as Atlantic—but not to this extent. The sheer volume of it has choked beaches and affected tourism from Trinidad to the Carolinas. Biologists cite rising sea temperatures as one reason for the algae’s proliferation, which means this weed isn’t going away anytime soon.

If you can look past the stench of decomposing weed on the beaches and the nuisance value of its clogging your engine water intake, Sargassum weed actually has a lot going for it. It’s a home and food source for a vast assortment of marine life forms—sea turtles apparently love the stuff—and has been described as “the rainforest of the oceans.”