Kimberly Miller
A reprieve from the unruly seaside assaults of prickly and putrid sargassum may end this summer as a record-challenging bloom of the pelagic weed swells in the tropical Atlantic.
Researchers at the University of South Florida said that an estimated 13 million metric tons of seaweed in the waters between Africa and the Caribbean tops the previous March record of 12 million metric tons and that it is only expected to multiply as the peak months of June and July close in.
“We predicted back in December and January this would be a major year, but no one was certain whether it would be a record year,” said USF oceanography professor Chuanmin Hu. “But now we already have a record March, and we have some confidence that this will be another record year.”
It is a similar message to what was announced the past couple of years when the so-called Great Atlantic Sargassum Belt reached record proportions in the early months of the year.
But the blooms ultimately deflated by summer leaving beaches mostly clear. The end-of-season record is a total of 22 million metric tons measured in 2022.
Why could this be a record sargassum year for Florida?
Florida Atlantic University research professor and algae expert Brian LaPointe said drought in South America the past couple of years led to less water flowing from the Amazon River into the Atlantic, which meant fewer nutrients to feed the fields of floating macroalgae.
This year, the Amazon is flowing again, LaPointe said.
“I’m looking closely at the influence of the Amazon and how that correlates with drought and the downturn in biomass production,” said LaPointe, who has already come across large mats of beached sargassum in the Keys. “We’re really coming out of that drought now.”
Hu said USF’s Optical Oceanography lab is seeing a “relatively large amount” of sargassum in offshore waters east of Florida. He believes the rapid-flowing Gulf Stream current will act as a barrier to it reaching beaches.
But it can also sneak up through the Florida Straits, threading the gap between the Gulf Stream and the coast. Winds have been blowing primarily out of the southeast this month, and there is sargassum showing up on some Palm Beach County beaches.
Cameron Koehler, who works at Nomad Surf Shop in Boynton Beach, said he taught a surf lesson Tuesday, April 22 and was surprised at the amount in the water.
“It was gnarly out there. There was quite a lot of seaweed,” Koehler said. “I feel like it’s showing up a little earlier than normal and it was pretty thick in some places.”
His pupil, who was from Montana, was “definitely not used to it.”
“He kept kicking it off his legs and feet. It’s an itchy feeling,” Koehler said.
Scientists began noticing the proliferation of sargassum in 2011. Hu’s lab measures the sargassum by satellite and has images dating back decades.
Is climate change to blame for all the seaweed in Florida?
Hu said the proliferation of sargassum is tied to climate change as far as how extreme fluctuations in wet and dry years can affect the amount of nutrients reaching the ocean. Warmer sea surface temperatures make less of a difference.
“The water is already warm enough in the tropical Atlantic. Adding a degree or so would not change the story. It’s pretty much the nutrients.” Hu said.
The initial bump in growth in the tropical Atlantic Ocean may have happened when strong winds and ocean circulations pushed sargassum from the Sargasso Sea into the Atlantic in 2010, Hu said.
That jibes with a 2020 report that included research by the National Oceanic and Atmospheric Administration that linked the increase in sargassum to a 2009-2010 change to the negative phase of the North Atlantic Oscillation, or NAO.
The negative phase of the jet-stream meddling NAO means a strong shift in winds to the west and south. Those winds flushed enough sargassum out of the Sargasso Sea to establish a colony in the tropical Atlantic Ocean. There, the sargassum got more sunshine and a high dose of nutrients that also come from upwelling ocean waters, according to the report published in the journal Progress in Oceanography in March 2020.
Why do we measure sargassum blooms?
Hu said it’s important to collect sargassum measurements to keep track of changes in patterns and amounts, but also to help people make travel decisions and for anglers or researchers looking for the bountiful array of life that hangs out in and under the floating mats.
A $3.2 million grant from the NOAA is being used in a USF project that can zoom in closer to better see the sargassum. While it’s being tested in the Keys, the plan is to extend it to waters off Palm Beach, Broward and Miami-Dade counties.
“The new system relies on satellites that provide data at a scale of about 50 meters, as compared to several kilometers in our current system,” said USF Professor Brian Barnes in a March announcement. “Thus, instead of looking at sargassum inundation at the scale of the Florida Keys region, we are now able to see potential impacts at an individual beach scale.”
Is it safe to swim in sargassum?
Sargassum is a lifeline for fish nurseries, hungry migratory birds and sea turtle hatchlings seeking shelter in its buoyant saltwater blooms. But in mass quantities, it chokes life from canals, clogs boat propellers and is a killjoy at the beach, piling up several feet deep like a rotting bog emitting hydrogen sulfide as it decomposes.
It's generally safe to swim in but can turn the water an uninviting brown and be uncomfortable when it scratches against your skin.
Why don't they just clean seaweed off Florida beaches?
Palm Beach County beach managers are often constrained by turtle nesting season, which began March 1. Most cities have specially licensed contractors who use tractors to clear the sargassum at least twice a week, but they are confined to areas below where turtles may nest.
Kimberly Miller is a journalist for The Palm Beach Post, part of the USA Today Network of Florida. She covers real estate, weather, and the environment. Subscribe to The Dirt for a weekly real estate roundup. If you have news tips, please send them to [email protected]. Help support our local journalism, subscribe today.