Happy sargassum season! From now until October, beachgoers in parts of Florida and the Caribbean can expect to clamber over massive piles of putrefied seaweed in order to access the ocean, and they can marinate in its hideous stench while they sunbathe on the beach. Per the Miami Herald, that ambience comes courtesy of the giant tangle of seaweed drifting across the Atlantic. To help you appreciate the meaning of giant in this context, some metrics: The blob is believed to measure 5,000 miles across. It may weigh as much as 6.1 million tons, and it is definitely visible from space. It is quite possibly the largest blob of its kind on record, and it’s currently due to make landfall in the Keys as early as next week, bringing with it the omnipresent odor of death.
Even though it sounds singularly bad, the blob is not, in and of itself, an oddity: Big flats of sargassum are naturally occurring in the Atlantic’s northern waters and have been making an annual migration from West Africa to the Gulf of Mexico since 2011, according to the New York Times. The problem is that the blob gets bigger every year, “and this year looks like it’s going to be the biggest year yet on record,” Brian Lapointe, a research professor at Florida Atlantic University who studies sargassum, told the Times. Already in January, the blob weighed in as the most immense blob of any other month on record. “This is quite early to see this much, this soon,” Dr. Lapointe observed of the blob, which has presumably only gathered strength in intervening weeks. And, yeah: To help you get your head around the estimated size of the blob’s final form, consider that the continental U.S. spans about 3,000 miles coast to coast.
While the blob remains seaborne, everything is fine: It offers safe harbor to fish and crabs and jellyfish and sea lice as it floats peaceably along its path. Problems arise when it rears over the waves and creeps onto the sand, as it bleeds oxygen from the water, bakes in the sun, and farts out rotten-egg-smelling gasses. The olfactory hellscape is not only a deterrent to tourism, it’s potentially also a threat to people with respiratory issues. And on top of all that, sargassum is difficult to dispose of because, as Dr. Lapointe noted to the Times, it contains arsenic.
Predictably, this menace is almost certainly man-made. Per the Herald, sargassum feeds on phosphorus and nitrogen, the former of which gets mixed into the water by violent storms and strong Saharan winds, and the latter of which humans feed into the sea by dumping their sewage and waste into rivers. Lapointe believes that the burning of fossil fuels also contributes, creating a blob that blooms with escalating ferocity each season. The onslaught of seaweed is gross for locals and tourists alike, and it smothers the ecosystems it meets as it approaches the shore: coral reefs, beds of turtle eggs, and mangroves are just a few examples. It’s also expensive to clear, blobs of years past having prompted the Mexican government to send in its navy and the Virgin Islands to declare a state of emergency after sargassum choked St. Croix’s desalinization plant. The Herald reports that Miami-Dade county already spends millions each year on the war against seaweed.
Right now, at this very moment, the blob is cruising for Florida, its barrier islands in particular. Cancun, Playa del Carmen, and Tulum anticipate the arrival of up to three feet of seaweed. That’s sargassum season for you — a time to lie on the beach and rot.