Seaweed invades the beaches
Cities clear mounds daily, for sake of tourists, turtles
Thick mats of seaweed have washed up on South Florida beaches in recent weeks, creating a tangled, squishy barrier between swimmers and the ocean.
The seaweed, a brownish variety called sargassum, arrived largely from the Caribbean, where rotting seaweed has piled up on beaches and driven away tourists. Hoping to keep South Florida’s beaches clear, cities are disposing of it, composting it or mixing it with beach sand.
“It’s been a challenge over the past couple of weeks,” said Raelin Storey, spokeswoman for Hollywood, which mixes the seaweed with sand, allowing it to remain on the beach and prevent erosion. “We’ve seen a tremendous amount of it, and we’re struggling to keep up with it.”
More than 1,000 square miles of seaweed have been detected in satellite photos of the Caribbean, three times larger than the 2015 record, according to an analysis by scientists at the University of South Florida’s Optical Oceanography Laboratory.
Caribbean newspapers are filled with news of rotting seaweed carted away in trucks, dead dolphins and ruined tourist spots. From the Caribbean, the seaweed reaches Florida through the Gulf of Mexico, drifting first into the Gulf and then riding the Loop Current through the Florida straits to the east coast of Florida.
“This year is just extraordinary,” said Chuanmin Hu, professor of optical oceanography at the university.
In the ocean, rafts of seaweed known as “golden forests” provide habitat for crabs, shrimp, fish and young sea turtles. On land, where the ragged line of seaweed paralleling the shore is called wrack, it attracts insects, crabs and other small creatures, which in turn attract birds.
But while the seaweed provides a long buffet table for many beach inhabitants, it’s less attractive to those beach inhabitants who arrive with umbrellas, sunscreen and paddleboards.
On a sunny morning in Delray Beach, thick, tangled blobs reached two feet high in spots, but swimmers picked their way across to reach the water. Offshore, brownish green mats of seaweed drifted
toward the beach. Heavy earth-moving vehicles lumbered along the beach, clearing the seaweed.
At a beach-oriented summer camp, the seaweed complicated a day of surfing.
“Because of all the seaweed, it’s difficult to get all the kids out, with his huge blockade,” said Jacob Serody, a supervisor in the camp, as the children played in the water. “A lot of the kids don’t like the critters that live in the seaweed, the crabs, the shrimp. Swimming through it is a mess. You get scratched up, and you get sea lice.”
Most people just lived with it.
“It’s nature,” said Megan Pollit, a part-time resident enjoying the beach with her teen daughter. “You wouldn’t pay extra for it, but it’s not hurting me.”
But it can hurt baby sea turtles, since its slimy tangles constitute a formidable obstacle between newly hatched turtles and the ocean.
“When the hatchlings start hatching out, this could be a problem for them,” said Kirt Rusenko, marine conservationist at Gumbo Limbo Nature
Center in Boca Raton, who runs that city’s sea turtle protection program. “It’s a lot of material to crawl over if you’re only a couple inches long.”
The reason for the heavy growth of seaweed remains unclear, said Hu, of the University of South Florida. Among the theories are climate change, ocean pollution and changes in the structure of ocean currents.
“That’s a good question that nobody can answer,” Hu said. “It’s easy to point fingers, but we don’t have scientific evidence.”
Brian LaPointe, a scientist at Florida Atlantic University’s Harbor Branch Oceanographic Institute, said the massive increases in seaweed appear to be related to the greater availability of the plant nutrients nitrogen and phosphorus. But why their concentrations have increased remains a mystery.
These could arrive in the ocean from sources such as rainwater washing off farms, dust carried off the Saharan desert, air pollution or discharges from the Amazon River.
“It’s a lot of material to crawl over if you’re only a couple inches long.” Kirt Rusenko, marine conservationist, referring to turtle hatchlings