As sargassum season around South Florida and across the Caribbean becomes a growing calamity for beachgoers and wildlife, researchers have landed on what they hope is a sustainable fix: Use the seaweed to feed the world.
If it works, the plan could provide a low-cost mobile solution that relies on nature to heal itself.
Using larvae from voracious black soldier flies, researchers at the University of Miami Rosenstiel School’s aquaculture program have successfully converted sargassum in a fraction of the time needed for traditional composting. Once fattened up, the larvae can then be used to feed livestock, fish, even cats and dogs. The larvae poop can be used for fertilizer.
“The idea is to provide local governments or local municipalities with either a tool or an additional tool to manage the sargassum in a relatively rapid cycle,” said researcher Julio Camperio, who's leading a two-year pilot project.
“If you can set up multiple containers in different areas to alleviate some of that pressure, that would be a huge win for us.”
And for beaches.
Up until about 2011, rafts of sargassum floating around the Atlantic, Caribbean and Gulf of Mexico were generally swept by a massive gyre into the North Atlantic, where they stayed put.
“Seaweed is nutrients at the end of the day. So can we use those nutrients, that seaweed, and feed it to the larvae?”Julio Camperio, University of Miami Rosenstiel School researcher
But according to research by the National Oceanic and Atmospheric Administration, prevailing winds, known as the westerlies, underwent a critical shift to the east between 2009 and 2011 that blew the seaweed off its historic course and spread it far wider.
The far-flung weed then seeded the new Great Atlantic Sargassum Belt, eventually sending more robust waves of sargassum to Florida beaches and the Caribbean, a team of researchers announced in an April study.
Previous theories that blamed the sargassum explosion on increasing nutrients from fertilizers flowing from the Amazon and Congo, Saharan dust or changing temperatures and currents driven by climate change failed to fully explain year-to-year variations, the researchers argued.
Instead, they say the shifting winds acted like a mixer that stirred up deeper, nutrient-rich waters to fertilize the patch. That attracted hungry fish, sea turtles and other marine life, which then added even more nutrients to create a self-sustaining ecosystem.
Dubbing it the "sargassumsphere," the mat "is much more than just seaweed. It is like a floating city,” and more like a mobile reef or forest, they wrote.
While a new ecosystem may be good for the ocean, on beaches where it begins to rot, sargassum can become a smelly mess, loaded with arsenic and heavy metals that can repel tourists. In 2025, scientists estimated the economic toll on southeast Florida alone has exceeded $2.5 billion. Miami-Dade County spends about $4 million a year to clean county beaches.
Black soldier fly
Enter the wasp-sized black soldier fly.
Using the fly's larva to convert organic waste has been around for decades, but more recently has surged in use, thanks to increasing global waste.
Camperio, the UM researcher, first learned about the flies while working at the Smithsonian’s Tropical Research Institute in Panama where he was recruited to help frog researchers trying to jump start the disappearing wild populations of harlequin toads. In college he’d gotten a job feeding fish at the New England Aquarium so started pursuing research on sustainable food.
An entomologist at the research station suggested he look into black soldier flies.
“They'll eat anything that they're given as long as it's provided to them in the right consistency, the right temperature, the right humidity and the right life cycle,” Camperio said.
In just nine to 14 days, hungry larvae can fatten and mature, ready to be ground into meal for food.
When Camperio enrolled in Rosenstiel’s aquaculture program, he was assigned the job of tending to fish in their experimental hatchery, where researchers raise cobia, mahi and other fish to help develop more sustainable ways to farm fish. Once again, Camperio turned to black soldier flies in search of more sustainable fish feed for the growing aqua culture industry.
“There's so much food that gets wasted on the farm because it's damaged, because it's not nice enough and it doesn't make it to the end product, to the end consumer,” he said.
So he began collecting dinged up mangoes and bananas from local farms, sludge and offal from a Homestead salmon farm, even leftovers from UM’s campus cafeteria. The fly larvae gobbled them up.
Then came an "aha" moment.
“We realized we have this huge bloom of sargassum that comes in on cycles every year, and it keeps getting worse and worse and worse,” he said.
Sargassum is too salty for the larvae to eat by itself, so he began experimenting with recipes. Mixing it with farm and fish factory scraps also helps reduce organic waste.
The larva “increases its size exponentially, converting all that food waste into larval biomass,” Camperia said. “Then that larva can be dried, turned into a powder, and that becomes insect meal, which you can use to make fish feeds.”
In 2025, the association that sets nutrition standards for feed approved black solder fly meal for livestock. The larva’s poop, which it creates in dried powder form like termite dust, can be used for fertilizer.
Arsenic and heavy metals
However, because sargassum contains arsenic and heavy metals, before it can be used, Camperio needs to be sure none of those chemicals are getting passed along. Traditional composting with sargassum has been used in places like Fort Lauderdale to lower costs, but has restrictions on its use because of those toxic chemicals. In 2022, UM worked with the city of Hallandale to test the safety of such composting and found that while compost produced by sargassum could be used commercially, there were limits on residential and food use.
At least one study has shown the fly larvae can break down the arsenic and turn it into something non-toxic.
”Feeding invasive marine seaweeds to larvae, there isn't too much information out there,” he said.
Over the next two years, Camperia hopes to provide more of that information. During the first year, he plans on developing recipes for the flies and a strategy to eliminate arsenic. The second year will focus on creating “mini black soldier fly farms” and mobile breeding labs so solder fly composting stations can be set up where the sargassum piles up.
“Seaweed is nutrients at the end of the day,” he said. ”So can we use those nutrients, that seaweed, and feed it to the larvae?”
