Brace for the seaweed invasion, Florida. It could be biggest ever

Scientists at the University of South Florida Optical Oceanography Lab, the point people for tracking the floating mats of seaweed called sargassum, are predicting what could be the state’s worst seaweed season. In the latest report issued April 30, they project 40% more seaweed than the previous record mess of 2022, when stinky, scratchy piles sent many tourists packing and cost cities millions to clean up.

The mass of seaweed, which piles up on beaches and collects around marinas and docks, is also forming earlier than usual out in far-off ocean waters. The bloom began in March and reached unprecedented levels by the end of April, said Chuanmin Hu, the professor who runs USF’s Optical Oceanography Lab.

What’s to blame? Wind, nutrients, and higher temperatures due to climate change could all be impacting how the sargassum belt forms and moves, he said.

“The speculation is that this spring, the water temperature is higher than usual in the western Atlantic and the Caribbean Sea at the right time,” Hu said. “And when it’s above the norm, the plants would be happier.”

Not so happy are people trying to swim around the stuff or breathing in the fetid aroma of drying mounds of sargassum.

When Sandra Abi-Rashed went to catch some waves at Haulover Beach at the end of April, she said it was like “surfing in a pool of seaweed.” She forgot her rash guard at home that day and came out with sea lice. She has been back since and said the conditions have been much better, but it varies from day to day.

At South Point Pier, beachgoers had to lift their knees to their chest to get through the seaweed lining the ocean on Wednesday. The smell was tolerable but most of the seaweed had just recently drifted ashore. Shorebirds picked through it for little crabs, insects, and worms. It didn’t bother everybody. One woman sunbathed along the shore, oblivious to globs at her feet. Some kids tried to make the best of it, decorating their sandcastles with the brown algae.

By Thursday morning, the beach was clean with tractor marks left over from the cleanup.

The costly cleanup bill

Miami-Dade County spent $2.8 million cleaning up seaweed in 2020, a figure that rose to $3.9 million during 2022’s record season. The county did not respond to comment before publication on how much the clean-up has cost so far this year.

Beyond costing a pretty penny, there are environmental and climate concerns with dumping all of the organic material into the landfill. As it decays, it turns into methane, a potent greenhouse gas warming the atmosphere.

At Crandon Park on Thursday, Myles Bleahen, 23, who traveled to Miami from Ireland, was surprised to see the mounds of seaweed coating the beach were being trucked off to the landfill. He said in Ireland, he went on a foraging tour to find edible pieces to put in soup or salads.

“It’s part of the ecosystem and we shouldn’t mess with it, ” echoed his dad, Finbar.

While some seaweed is edible, sargassum seaweed found in Florida is generally not recommended to eat due to potential health risks. Sargassum releases a hydrogen sulfide gas that can irritate your eyes, nose and throat and contains signs of heavy metals.

Miami-Dade is looking for a better solution will what to do with all the seaweed trucked out of sight from tourists daily. The Miami-Dade Innovation Authority gave four start-up companies $100,000 to find a more beneficial way to recycle seaweed. Some ideas include turning it into fertilizer, green hydrogen and biofuels. At least two of the companies are going to start testing their solutions this summer.

Working on better predictions

Although the USF scientists measured some 30 million metric tons of seaweed with satellite imagery, they can’t say how much of that will come our way, or which beaches will see the worst of it. The lab, which received a $3.2 million grant from the National Oceanic and Atmospheric Administration, is working towards being able to better zero in on predicting where sargassum will eventually wind up.

Josefina Olascoaga, a professor of ocean sciences at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, researches seaweed’s movement. Recently, she used the university’s wind-wave-storm simulator to track how the sargassum moved in different currents and winds. Eventually, she’d like to create a mathematical model to predict the seaweed’s dreaded arrival.

Olascoaga said that some studies suggest that too hot water temperatures could actually hurt the seaweed’s production.

That’s what happened last year when USF’s experts predicted a “major sargassum year” based on the huge swaths of seaweed they saw in the Atlantic. It did not materialize.

There are some upsides to the seaweed: Charter boat captain Nelson De La Torre, a seasoned fisherman with over 30 years of experience, said it might get tangled in lines or lures, but it does bring in an entire ecological system. He offers deep sea fishing adventures with Billin Office Fishing Charters at Crandon Park marina.

“You got fish eggs, jellyfish in there,” said De La Torre, who runs Billin Office Fishing Charters at Crandon Park marina. “The mahi come in and get chased by the marlin and the billfish. And then the white-tipped sharks come and get the scraps of anything the marlin kills. It’s like a big McDonald’s.”

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