The seaweed monster is back devouring South Florida beaches. It’s not a pretty sight

Adriana Brasileiro
·5 min read

Like most tourists coming to a South Florida beach for a quarantine break, the Mlynek family had a picture-perfect scene in mind when they arrived from Oklahoma this week: turquoise waters glistening in the sun, gently swaying palm trees and shining stretches of white sand.

What they found in Hollywood instead were smelly, messy mounds of coating the coastline.

Seaweed is once again invading Southeast Florida beaches as mats of the massive macroalgae swirling around in the Atlantic make their annual appearance. But this year is shaping up to be a really bad one: a combination of ocean currents and seasonal southeasterly winds is moving the nasty stuff over from the eastern Caribbean, fouling vast expanses of sand and turning nearshore waters into a slimy soup.

“It’s a bit disappointing, definitely not what we expected,” said Mike Mlynek, a Red Cross executive who booked a vacation at the Margaritaville Hollywood Beach Resort hoping to swim in a pristine beach for a week.

Seaweed, or sargassum, is a natural occurrence, regularly washing up on beaches around the Atlantic, the Gulf of Mexico and the Caribbean. But it has become a major headache over the past few years, blanketing popular tourist destinations like Cancun, where the Mexican Navy is using ships in cleanup operations, and Barbados, where the Prime Minister said sargassum is as big a threat to the local economy as a hurricane.

Monica Madrigal, a Miami Beach resident, find her way out of the ocean through a thick layer of slimy seaweed.
Monica Madrigal, a Miami Beach resident, find her way out of the ocean through a thick layer of slimy seaweed.

So far it hasn’t been as bad as the sargassum attack of 2018, when a record-breaking crop blanketed beaches from Key Biscayne to Jacksonville. But it’s worse than scientists thought it would be when they calculated predictions earlier this year, said Chuanmin Hu, professor of optical oceanography at the University of South Florida. His lab tracks seaweed movements based on NASA and NOAA satellite images.

“Several months ago we predicted this would be a bad year, but not as bad as 2018; We’ve already seen a whole lot of sargassum reaching our shores faster than we expected,” Hu said. “At this point it’s looking like things are actually worse than our original estimates.”

The total amount of sargassum in the Atlantic is bigger than what satellites registered last year, which is not very encouraging, he added. Over the next two weeks Florida’s east coast will likely see another wave of heavy blooms covering beaches.

In June, vast mats of sargassum continued to increase across the central Atlantic, creating what scientists have dubbed the Great Atlantic Sargassum Belt. Over the past few years, this 5,500-mile seaweed blanket stretching from West Africa to the Gulf of Mexico has become a permanent occurrence.

In June 2018, the belt was at its thickest, containing more than 20 million metric tons of seaweed — heavier than 200 fully-loaded aircraft carriers. Last month, the total seaweed amount increased to 12.7 million metric tons compared with 8.7 million metric tons in May. In June 2019, sargassum amounts in the Atlantic totalled about 10 million metric tons, Hu’s Sargassum Watch System shows.

Looking ahead, more seaweed will move up the east coast of Florida in August, while the eastern Caribbean will continue experiencing large amounts through September 2020 with many beaching events, Hu said. The western Caribbean will also experience moderate to large amounts.

The algae is not a killer of marine life like red tide or toxic to humans as harmful algae blooms.

In normal years, sargassum is actually a good thing: the Sargasso Sea in the North Atlantic supports a wide range of species and plays a crucial role in sustaining the early life cycles of whales, dolphins and migratory birds. Baby sea turtles make their way from sandy beaches in Florida and the Caribbean toward the seaweed, finding food and shelter from predators during their first years of life. It’s also a haven for species that live nowhere else, like the Sargassum fish, a frog-like fish whose appearance mimics the seaweed.

In Fort Lauderdale, a tractors mixes seaweed with the sand but cleanup efforts are not enough to clear the beach of the smelly sargassum.
In Fort Lauderdale, a tractors mixes seaweed with the sand but cleanup efforts are not enough to clear the beach of the smelly sargassum.

Beaches in the Caribbean, Florida and the Gulf of Mexico would historically experience small, manageable amounts of the floating algae until 2011, when unusually large beaching events occurred in all those areas. In late 2009 and 2010, an unusual pattern of winds and surface seawater circulation took place in the Sargasso Sea, taking the algae to new places and expanding its range. An extraordinary number of sunny days and more phosphorus-rich dust blown from the Sahara may have also contributed to the algae explosion.

Scientists also believe that an increase in fertilizer runoff from the Amazon and Mississippi River basins may be contributing to the blooms.

The reasons may not be fully understood yet, but the result is that massive amounts of sargassum seem to have become the new normal, said Stephen Leatherman, director of the Laboratory for Coastal Research at Florida International University. In large quantities, it can prevent newly hatched sea turtles from reaching the water and can get tangled in boat propellers, not to mention the stench as it decays.

“Sargassum is a huge issue for destinations like Barbados or Cancun in Mexico because it’s chasing tourists away,” he said. The Mexican navy is building a fleet of ships to collect the blooms before they reach its famed beaches while Barbados has called on other Caribbean nations to come up with regional solutions to deal with the scourge.

In Hollywood, the city has been using modified tractors to mix the seaweed with sand early in the morning to get the beach ready for visitors. But that wasn’t enough for Valeria Prieto, a visitor from Mexico City. She walked tentatively to the surf, tiptoeing around the thicker piles of sargassum. She quickly dipped her feet in the water and walked back to her beach chair.

“Even if things are better here than in other places like Cancun, it’s the same seaweed, and it’s just nasty,” she said.