Sargassum Crisis on San Pedro Beaches!!!

You may well be asking – “So, what in the world is Sargassum, and what possibly could be the problem?”

Sargassum is a genus of brown macroalgae (might commonly be called seaweed) that can float at sea owing to the presence of berry-like, gas-filled bladders that provide buoyancy (Photos 1 & 2). Numerous species of Sargassum are present in the tropical and sub-tropical oceans of the world.


Photo 1: Close-up image of a piece of Sargassum from the beachfront of the Mayan Princess Hotel in San Pedro. Note the berry-like float structures.

Photo 2: Typical small mass of Sargassum floating near our patch reefs study area at Mexico Rocks, north of San Pedro. We observed numerous similar small masses on every dive.

In the western North Atlantic, the so-called “Sargasso Sea,” located south of Bermuda and east of Florida and the Bahamas, takes its name from the large masses of floating Sargassum that occur there. This was an ocean area that early western European navigators tried to avoid for fear of having their sailing ships becoming entangled in the floating masses.

Sargassum is not new to San Pedro beaches. What is new is the hugely increased volume of Sargassum that is washing up daily on Belizean beaches and elsewhere in the Caribbean. Reports of increased Sargassum throughout the Caribbean date back to 2011, with the primary source traced to South Atlantic waters off northeast Brazil and the mouth of the Amazon River. That’s a long and tortuous ride to Belize, but satellite images confirm this. Causes for the “Sargassum explosion” are not fully known and understood, but increased nutrient loading in coastal waters and warming ocean waters likely are contributing factors. You can check online for more information about the bigger picture – there are plenty of recent posts!

The big problem along coastlines like that of Ambergris Caye is that the Sargassumwashes into the very shallow waters of the beach zone and then gets stuck there (Photo #3). The Sargassum bakes in the shallow water, dies, and settles to be bottom, where the sheer mass of the algae smothers the underlying, naturally occurring beds of turtle grass that are so important to the nearshore ecosystem.  Even worse, the decaying mass sucks up all available oxygen in the shallow water column, resulting in very nasty water and fish kills.

Photo 3: Accumulation of Sargassum on the Mayan Princess Hotel beach over a 24-hour tidal cycle, June 19-20, 2018. This is nowhere near as extreme as the accumulations earlier this year (Photo 4), but it is far more Sargassum than what we have seen in June in previous years.

Photo 4: This is a major problem! San Pedro beaches were inundated by Sargassum in the spring. Photo courtesy of the San Pedro Sun newspaper, 30March18.

Significant fish kills were reported earlier this spring at several locations along the ocean-side coast of Ambergris Caye. The Coral Ed team has noted that the numbers of fish around the docks of Amigos del Mar (our long-time dive operators) are low, and the large sting rays that all enjoyed watching in the past now are MIA! As stated earlier, the Sargassum also is a real problem for beachfront hotels and restaurants plus for San Pedro city government officials in terms of the costs of Sargassum removal and disposal (photos 4 & 5) and “what to do next.”

Photo 5: Currently, workers of the city of San Pedro are raking up Sargassum daily, and large piles are everywhere. Needless to say, the piles are smelly and unsightly – not good for a tourist town and expensive to manage. Also, there is a big question as to just what to do with all this “stuff?” We have heard that the Sargassum is being burned somewhere outside of town, but this is unconfirmed. Casual dumping of Sargassum is occurring widely.

“Tropical Paradise” is very much an overused phrase for resort islands like Ambergris Caye. The citizens of “La Isla Bonita” face many challenges, both economic and environmental. Some issues are within direct control of the city council and environmental managers, including over-development, traffic control, trash removal, and over-fishing. Others, such as the threat of hurricanes, deteriorating coral reef health, and the “Sargassum crisis,” are global issues beyond direct local control. How both island residents and the global community address these challenges are open questions, with answers to be determined in the future. In any case, my guess is that no local city council or island-planning group could have seen the “Sargassum crisis” coming…

By Al Curran

5 thoughts on “Sargassum Crisis on San Pedro Beaches!!!

  1. Interesting blog post. Your pictures clearly illustrate how this is a problem for San Pedro. This issue looks quite similar to the nuisance algae we have here in the Great Lakes with Cladophora. Similar reasons as in San Pedro: excessive nutrients and warming waters. In the Great Lakes we have the additional problem of invasive Dreissenid mussels that concentrate nutrients in the nearshore, which helps promote algae growth. Different water bodies, same concerns….

  2. How awful for all in San Pedro. Terrible to think what this is doing to all those little undersea communities we used to watch off the docks. My first thought was of Lake Erie in the mid-60’s when industrial waste caused huge fish kills and tons of algae to accumulate near the shore. We had to wade to chest-deep to get to water and it sure stunk. Thanks for the update, Al. Hope all is well with you!


  3. Those photos are hard to imagine knowing the beach scape of the past. Thanks for updating us all on this issue and it is so good to know that the team is thinking about it!

  4. Al, A similar-looking “seaweed” in New England-Maritime waters, a species that attaches to rocks and is exposed in the intertidal zone, is both an “industry” and an integral part of the ecosystem. It’s harvested at lowtide by cutting above the roots to ensure regrowth and sold to fertilizer company for $50/ton. It’s dried, ground and sold as a soil supplement. The problem there is that the harvesting disrupts the ecosystem when overdone, and scraps wash up on shore forming a smelly mess – reminding me of your informative photos. At this time, I can only offer the suggestion to consider the potential use for the beached-weeds as a fertilizer. Of course, the entire situation stinks. Good luck on identifying and eliminating the cause.

Leave a Reply

Your email address will not be published. Required fields are marked *