The sargassum seaweed has piled up several feet deep in South Florida and other regions, becoming a plague for tourists and wildlife alike. It also rots quickly on land and creates a stink.
“It’s much worse today than it’s ever been,” said Stephen “Dr. Beach” Leatherman, a professor at Florida International University in Miami. “On the Gulf Coast and in South Florida, there’s always been some seaweed, and it was dealt with by plowing it under the sand. But they can’t plow it under now, because it’s just too much. So they have to haul it.”
Sargassum seaweed is a type of brown or yellowish algae, like kelp or the more commonly eaten wakame found in typical seaweed salads. It can be used as fertilizer if composted properly, and can be eaten if cleaned and cooked properly.
But it is not considered to be among the most edible seaweeds because of its rough texture and bitter taste, according to a report from the Caribbean Alliance for Sustainable Tourism. Research has shown that it can contain toxic heavy metals.
Miami-Dade County in Florida alone has estimated hauling all the seaweed would cost $45 million per year. The county’s parks department received special permits from the state in early August to use bulldozers, tractors and raking machines during hatching season for sea turtles.
The county is trying to haul away only the worst spots and chop up or bury it in other areas, a combined approach still estimated to cost millions of dollars per month.
Upscale areas in Palm Beach and Broward counties in Florida have been impacted by huge deposits of seaweed, which drive vacationers away from the beaches and toward alternate ways to enjoy vacations or time off from business events.
Leatherman concurred that seaweed is having a dramatic effect on the popularity of certain beaches, and he will have to take it into account on his annual ranking of the best beaches in America.
One chain of beach resorts in the Caribbean, Bahia Principe, claims on its website and on social media that it installed barrier systems that reduce seaweed on its beachfronts by 95 percent. It has several resorts on the north coast of the Dominican Republic.
Many universities in Florida and the Caribbean have tasked scientists to figure out why the last few years are seeing huge blooms of the seaweed, which is considered a large type of algae.
The name sargassum comes from the Portuguese word for seaweed, and it was attached to the Sargasso Sea — part of the North Atlantic Ocean were the algae often bloomed in large mats as far back as the 15th Century.
Seaweed from that area has throughout history broken off and washed up on beaches around the region. But research shows a marked increase over the past ten years, and a spike in the past three years.
“It’s always been known that the Amazon River in Brazil supplies nutrients that lead to algae blooms,” Leatherman said. “In recent years, studies have shown that deforestation and agriculture in the Amazon, along with heavy rains, have increased the nutrients.”
Cassandra Gaston, assistant professor at the University of Miami, participated in a study released this year that also found higher than expected nutrients from smoky fires in Africa being deposited into the ocean.
“It’s certainly becoming worse and worse in recent years. It’s really been a major, major problem especially for the Caribbean,” Gaston said.
She noted that the island nation of Barbados declared a national emergency in 2018, calling out the military to deal with the problem. The government of Trinidad and Tobago issued public seaweed warnings in 2018 to caution beachgoers and fishermen.
The Belize Tourism Board formed a Sargassum Task Force in 2018, which has distributed $1.5 million to beach towns most affected, including San Pedro, Caye Caulker, Hopkins and Placencia. The task force also arranges disposal sites, awareness campaigns and seaweed forecasts.
“We found that African dust storms are certainly playing a role, but we saw a lot of nutrients coming from African smoke,” Gaston said. “It might be playing a role in the sargassum. Right now, we don’t know the exact role it plays with sargassum and we are doing a lot more work to understand it.”
Temperature and weather also plays a role in the seaweed growth, with large blooms being tied to cooler years, and to patterns that follow major hurricane activity.