‘A new normal’: Miami faces worsening algae problem as piles of seaweed wash up on beaches | Miami

Treating seaweed is the majority of Chris Bumpus’ work during the summer. As chief conservation officer for Miami-Dade County’s parks, recreation and open spaces department, Bumpus is in charge of cleaning sargassum from 17 miles (27 kilometers) of county beaches. But some days, the odds are against you and your team.

More and more sargassum, a species of floating brown algae, is washing up on beaches in southern Florida, West Africa, the Gulf of Mexico and the Caribbean.

Most mornings this time of year, a member of Bumpus’ seaweed team walks to South Beach around 7 a.m. to take photos of piles of spicy mustard-colored seaweed before a dozen tractors and specialized beach-combing vehicles get to work trying to integrate the sargassum into the sand or rake it for transport. “In July, the beach was clean for about an hour,” Bumpus said. That month alone, 9,000 tons of seaweed were removed from Miami-Dade County beaches, more than ever in a single previous month.

“Hopefully by October it will have subsided,” he said. “Julio is always the worst. It’s been a tough season.”

Before the cleanup begins, a team has already marked the new sea turtle nests so that they will not be damaged by the removal of the sargassum. The county has a permit from the Florida Department of Environmental Protection to use heavy equipment to corral the algae. The permit prohibits such equipment during turtle nesting hours, from 30 minutes before sunset to sunrise. So far this nesting season, about 700 sea turtles have built nests on the county’s beaches.

Miami-Dade County spends $3 million a year on sargassum removal, more than any other county in Florida, Bumpus said. The Florida Keys, however, may see greater accumulations of sargassum due to the inlet shape of their beaches, he said. For centuries, sargassum has grown in the Sargasso Sea, a region of the North Atlantic surrounded by ocean currents that keep the algae concentrated there. But in 2011, scientists first saw the Great Atlantic Sargassum Belt forming, stretching from West Africa to the Gulf of Mexico. Scientists say several factors contribute to the bloom, including nitrogen and phosphorus from rivers (such as the Amazon, Congo and Mississippi), warmer water temperatures and ocean circulation.

Since 2011, the amount of sargassum has doubled every five years, as a result, larger and denser sargassum mats have been appearing in Mexico, Florida and the Caribbean. This summer, satellite images showed the second-highest amount of sargassum in the Great Atlantic Sargassum Belt, at a whopping 33.5 million tons, slightly behind 2025, when seaweed biomass reached 38 million tons.

Side by side photographs of sargassum on the beach and a cleaning vehicle on the beach

The climate crisis has also played a role in the proliferation of sargassum, said Brian LaPointe, a research professor at the Port Branch of Florida Atlantic University, who has been studying sargassum since 1982. “As we see more warming of the oceans, we have more evaporation and that drives these extreme rainfall events that essentially dump more nutrients from the land into the ocean,” he said. “So that’s an indirect effect that can increase the nutrient supply to the sargassum.”

Miami-Dade County began working to address its seaweed problem in 2019. The county’s annual algae abatement budget is funded by tourism development taxes paid by visitors staying in hotels and short-term rentals. In July, Miami-Dade County commissioners voted to ask the state to allow the county more flexibility to use beach raking equipment in more areas.

“I think this year has been a game-changer because we’ve seen major flooding here in South Florida, more than we’ve seen in previous years, and comparable to what’s been happening in the Caribbean, Mexico and the Dominican Republic,” LaPointe said.

In Mexico, President Claudia Sheinbaum announced a $115 million national plan to combat sargassum, which includes the use of boats that extract the algae from the water. But U.S. federal and state agencies prohibit open-water harvesting of sargassum due to concerns about marine life living on floating mats of algae. But LaPointe said that could eventually change, as research in his lab shows that sargassum loses much of its marine life as it deteriorates and moves closer to the beach.

Sargassum serves as critical habitat in the open ocean, but that changes as it approaches and reaches the coast. “What we’re seeing is that as this excessive amount of sargassum comes ashore, it impacts coral reefs and seagrass beds and creates dead zones, which removes oxygen from the water,” LaPointe said. “That’s why we get these hydrogen sulfide odors, which poses a risk to human health.”

More aggressive algae removal efforts may be necessary, but these measures will not address the underlying causes of the increasingly massive blooms in the ocean, LaPointe said. “People are realizing that this is not going away. It’s getting worse. It’s the new normal. It’s not just about treating the symptoms but doing more research on terrestrial nutrient sources that we can do something about,” he said.