Until a few years ago, Sargassum, a free-floating brown seaweed that lives in the open ocean, was of very little interest to most scientists, and of no interest whatsoever to visitors to the tropical Atlantic. But what began as an odd expansion of range and surge in reproduction has culminated in the 2018 “summer of Sargassum”. In the past six months the seaweed has spread, virtually unchecked, throughout the Caribbean and along the eastern shores of Mexico and the southeastern US: New Republic reports that over 700 beaches have been fouled by sargassum this year.

Up close and personal with some sargassum.

According to NOAA, natural sargassum ecosystems support a wide variety of marine species. Turtles use the seaweed mats as nurseries where hatchlings have food and shelter, and sargassum provides essential habitat for shrimp, crab, fish, and other species that have adapted to the floating algae. The key word here is “natural”. The sudden proliferation of sargassum has sent scientists to the ocean and to the lab. Several theories have been floated, but no one seems to have a definitive answer.

Until now, the seaweed was primarily found in the Sargasso Sea, a unique patch of water in the North Atlantic. (The Sargasso is the only sea to be surrounded not by land, but by four ocean currents.) When massive rafts of sargassum first appeared in the Caribbean, it was assumed that the source was the Sargasso Sea, but satellite imagery has revealed a new source. The research behind this discovery is detailed in Pelagic Sargassum in the Tropical North Atlantic. An article in the journal Science explains that the “new source region is encircled by currents running clockwise from South America to Africa and back again. From January to May, that loop breaks down and westward flows sweep Sargassum up the Brazilian coast toward the Caribbean”.

I’ve traveled to Belize a few times a year for the past 12 years but sargassum has only been on my radar since 2015. Three years ago, I pitched a story about the issue, but it was turned down because the topic was deemed not particularly newsworthy. It’s certainly big news now! Big in terms of its impact on tourism and fisheries, and the daunting and unrelenting expense of cleaning it up. There are also substantial social and humanitarian issues. Many of the small island states affected by the seaweed don’t have the resources to tackle the problem effectively, and the influx of seaweed is impacting the health and quality of life of residents who must endure the fouling of their beaches. (And foul it can be! Although one gets used to it, the first morning whiff of hydrogen-sulphide-laced air from rotting sargassum can be a bit rough.)

Several articles have been written about this summer’s sargassum invasion, and there’s no need to repeat what’s been said. In June of this year, Hakai published The Eastern Caribbean Is Swamped by a Surge of Seaweed. Science journal reported that Mysterious masses of seaweed assault Caribbean islands, the Palm Beach Post wrote in August that Sargassum harasses South Florida during worst seaweed assault on record and Marlin Magazine printed The Sargassum Invasion: Addressing the issues of a weed-choked Caribbean

Waves drive sargassum up the shore.

But back to Belize. Three weeks ago, Mexico News Daily reported that the first section of a 27 kilometre-long floating sargassum barrier was installed at Punta Nizuc near Cancún. The barriers will stretch south to Chetumal, located near the border between Mexico and Belize. (The barriers are anchored to the seabed and are modified from those used to contain oil spills.) Belize is not a rich country, and many locals worry about the repercussions of seaweed being shunted down the coastline from just a stone’s throw north. (To be fair, the same concern has been voiced about the sea walls of resorts on Ambergris Caye shuffling the sargassum down the island where it accumulates in fat wedges in front of open-beach resorts and public areas.)

Rafts of sargassum ferry trash to the the shoreline.

Sargassum is impacting marine ecosystems in a number of ways. The large rafts of seaweed act like a conveyor belt ferrying trash to the beaches. The birds, however, seem to be enjoying the bounty. They treat the mats like a floating buffet, and either ride the waves, picking choice morsels from the surface, or soar high above, spotting fish feeding in the weeds.



A dead fish and a flip-flop sum up the saga of sargassum.


Sargassum can also suffocate marine life and stress corals, seagrass and sponges. As the seaweed decays, it can temporarily reduce oxygen levels, and floundering fish and dolphins have been trapped in the oxygen-starved water.





Workers clear the same patches of beach day in and day out.

In Belize, workers frequently stand in knee-deep water, pitchforks in hand, shoveling the seaweed out of the water. Others rake the beach or fill small trailers and wheelbarrows to cart the soggy mess “away”. Away can vary; sometimes the seaweed is used as fill for nearby eroded beaches and low lying areas, sometimes it’s used as compost or mulch, and sometimes it’s carted away to a local landfill.

The BBC reports that across the Caribbean, removal techniques have improved since the initial influx in 2011. Most techniques are land based, and range from simple, low cost, environmentally friendly clearing by workers with shovels and rakes to more expensive, intensive, and potentially damaging tractors and heavy equipment. A variety of methods have also been tried for shallow water removal, but results have been mixed. There have been issues with unwanted bycatch of marine life, unloading, and stability of equipment in the water ( e.g., booms, barges, and vacuums).

In Belize, most people are outwardly optimistic and look to the shore saying, “It’s just a bad year; it will probably be better next year”. My fingers are crossed, but I’m not holding my breath… (well actually, I am, but you know what I mean).

Maggie’s happy place in Belize.

With this story Maggie is saying “so long” to CaNOE. A member of the first board of CaNOE, co-chair of the Communications Working Group and creator of the monthly SPLASHmail for the past two years, she is excited to hand her paddle to an energetic and talented new crew. She will continue to edit and write about all things water (fresh and salt) as a freelancer, so you might run across her name here or there. If you want to chat you can contact her at maggie.romuld at gmail.com or you can follow her on Twitter or Instagram

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