For Chris Bumpus, summer in Miami isn't about sun, sand, and mojitos - it's about the relentless, slightly spicy-smelling brown stuff that keeps washing ashore. As chief of conservation for Miami-Dade County's parks, recreation, and open spaces department, Bumpus oversees the cleanup of sargassum along 17 miles (27km) of county beaches. Some days, it feels like a losing battle.
The sargassum - a floating brown algae - has been piling up with increasing fury on beaches from south Florida to west Africa, the Gulf of Mexico, and the Caribbean. Every morning this time of year, a crew member walks onto South Beach around 7am to photograph the seaweed piles before a dozen tractors and specialized beach combers try to mix the algae into the sand or haul it away. "Back in July, the beach looked clean for about an hour," Bumpus said. That month alone, 9,000 tons of seaweed were removed from Miami-Dade beaches - a record for a single month. "Hopefully, by October it will die down," he said. "July is always the worst. It's been a heavy season."
Before the cleanup, crews mark new sea turtle nests to avoid harming them. The county holds a permit from the Florida Department of Environmental Protection for using heavy equipment, which is prohibited from 30 minutes before sunset until sunrise to protect nesting turtles. So far, about 700 sea turtles have nested on county beaches this season.
Miami-Dade spends $3 million per year on sargassum removal - more than any other Florida county, Bumpus said. The Florida Keys can see even heavier accumulations due to their inlet-like beaches. Sargassum has grown for centuries in the Sargasso Sea, but since 2011, scientists have tracked the Great Atlantic Sargassum Belt, stretching from west Africa to the Gulf of Mexico. Factors fueling the blooms include nitrogen and phosphorus from rivers like the Amazon, Congo, and Mississippi, warmer waters, and ocean circulation.
Since 2011, sargassum amounts have doubled every five years. This summer, satellite imagery showed the second-highest amount ever in the belt: a whopping 33.5 million tons, slightly behind 2025's 38 million tons.
The climate crisis plays a role, says Brian LaPointe, a research professor at Florida Atlantic University Harbor Branch who's studied sargassum since 1982. "As we see more ocean warming, we get more evaporation and that drives these extreme rain events that essentially flush more nutrients from land into the ocean," he said. "So that's an indirect effect that can increase nutrient supply to sargassum."
Miami-Dade began tackling its seaweed problem in 2019, funded by tourist development taxes from hotel and short-term rental stays. In July, county commissioners voted to petition the state for more flexibility in using beach raking equipment in more areas.
"I think this year has been kind of a gamechanger in that we've seen major inundations here in south Florida, more than we've ever really seen in past years, and comparable to what's been happening in the Caribbean, Mexico, and the Dominican Republic," LaPointe said.
Meanwhile, Mexico's President Claudia Sheinbaum announced a $115 million national plan, including ships that scoop seaweed from the water. But US federal and state agencies prohibit open-water removal due to concerns for marine life. LaPointe's research suggests that as sargassum deteriorates near shore, much of its marine life is lost, which could change regulations.
Sargassum is vital in the open ocean, but when it piles up on beaches, it harms coral reefs and seagrass beds, creating dead zones that strip oxygen from the water. "That's why we're getting these odors of hydrogen sulfide, which presents a human health risk," LaPointe said. More aggressive cleanup might help, but it won't fix the root causes. "People are realizing this isn't going away. It's getting worse. It's the new normal," he said. "It's not only treating the symptoms but doing more research on the land-based nutrient sources that we can do something about."