Massive swath of brown algae angles toward Southwest Florida beaches, but need we worry?
WGCU | By Tom Bayles
Published March 24, 2023 at 7:21 AM EDT
A super-swath of brown seaweed is drifting toward Southwest Florida’s beaches, threatening to pile up feet deep in places and stink like rotten eggs as little creatures it calls home stand ready to sting anyone who touches the bio-mass.
The Great Atlantic Sargassum Belt — stretching from West Africa to the Gulf of Mexico — is arriving at about the same time the noxious red tide blooms that have been plaguing the region’s beaches for months are moving away.
The “blob,” as many in the media are calling it, has been making news for weeks. News accounts have the seaweed-like algae “drowning ecosystems” and “killing wildlife” after it “stifles tourism” by “turning nearshore waters into seething sargassum soup.”
There is even a sargassum monitoring webpage by “Christine” that allows folks to “follow the brown seaweed’s invasion.”
But one marine biologist at Florida Gulf Coast University, who calls the sargassum migration an normal, healthy environmental fact of ocean life, is worried the hyperbole has already done damage to public perception and a barely recovering tourism industry post-Hurricane Ian.
“I think the hysteria started when people started calling it a ‘blob.’ That invokes this horror story that was this movie way back when,” said Barry Rosen, an aquatic biologist at FGCU’s The Water School. “It is not a blob. It is a mass of living organisms pumping oxygen into the air. It’s a very nice ecosystem, and it typically doesn’t cause a problem.”
The brown algae travels from a place aptly called the Sargasso Sea in the North Central Atlantic every year. While biologists have recorded the mass growing to record sizes in the past five years, this year’s floating algae pile is setting no new records.
Rosen said sargassum piles in the Atlantic Ocean are critical ecosystems that serve as shelter for baby sea turtles and a host of other creatures until they grow larger.
In fact, sargassum has properties that can overwhelm red tide blooms like the ones plaguing Southwest Florida’s coasts for months. The brown algae also leaches natural substances that can prohibit new harmful algae blooms.
“I’m very uncomfortable that the media has taken this from an organism that’s been around for in the Caribbean at least a decade, if not longer,” Rosen said. “It’s a teeming healthy ecosystem. Is it going to come towards our shoreline? It’s a matter of circulation, not destiny.”
In other words, it may or may not make a sea-weedy landfall in Southwest Florida. And if it does, it may or may not be anything more than a morning nuisance for clean-up crews.
Certainly nothing in store like the mayhem depicted in “The Blob,” the classic 1958 movie, starring a young Steve McQueen, about a red mass from space: “It crawls! It creeps! It eats you alive!”
Here’s a look at this year’s sargassum seaweed bloom from the Associated Press:
What is it?
A leafy brown seaweed festooned with what look like berries. The seaweed floats on the open ocean and — unlike other seaweeds — reproduces on the water’s surface, helped by air-filled structures that give it buoyancy.
Sargassum originates in a vast stretch of the Atlantic Ocean called the Sargasso Sea, which lies well off the southeast U.S. The Sargasso has no land boundaries; instead, four prevailing ocean currents form its boundaries.
The matted brown seaweed stretches for miles across the ocean and provides breeding ground, food and habitat for fish, sea turtles and marine birds, according to the National Oceanic and Atmospheric Administration.
“It’s a dynamic, constantly changing set of pieces of this large mass,” said Rick Lumpkin, director of the Physical Oceanography Division at NOAA. “It’s not one big continuous blob heading straight to South Florida.”
Is it a problem?
Sargassum piles up on beaches where it quickly decomposes under hot sun, releasing gases that smell like rotten eggs.
In recent years, sargassum has carpeted beaches on some Caribbean islands and Mexico’s Yucatán Peninsula in the spring and summer months. Beach towns and cities and hotels have struggled to keep up with the huge amounts of seaweed that wash ashore.
The Great Atlantic Sargassum Belt — as the biomass stretching from West Africa to the Gulf of Mexico is called — contains scattered patches of seaweed on the open sea, rather than one continuous blob of sargassum. It’s not a new occurrence, but satellite images captured in February showed an earlier start than usual for such a large accumulation in the open ocean.
Once it washes ashore, sargassum is a nuisance — a thick, brown algae that carpets beaches, releasing a pungent smell as it decays and entangling humans and animals who step into it. For hotels and resorts, clearing the stuff off beaches can amount to a round-the-clock operation.
What about this year?
Some sargassum has already reached beaches in Key West, said Chuanmin Hu, a professor of oceanography at the University of South Florida. But most of it will arrive in the summer, Hu said.
“What is unusual this year compared to previous years is it started early,” Hu said. The algae generally blooms in the spring and summer, but “this year, in the winter, we already have a lot.”
Southern Florida, the Caribbean and the Yucatán Peninsula typically see sargassum piling up in the summer months and could expect the same this year, Hu said.
It’s a lot, but it’s been worse.
Scientists estimate there’s more than 10 million metric tons of sargassum in the belt this year. Lumpkin called it “one of the strongest years, but not the strongest” since scientists began closely observing the biomass via satellite imagery in 2011.
He said there was more in 2018. The years 2019 and 2021 also saw a great deal of sargassum, he said.
What causes it?
Scientists aren’t exactly sure, in part because it wasn’t closely monitored until 2011.
“We do know that to get a lot of seaweed, you need nutrients, and you need sunlight. Of course, as you get close to the equator, there’s going to be more sunlight,” said Mike Parsons, a professor of marine science at Florida Gulf Coast University.
Parsons and other experts say agricultural runoff seeping into the Amazon and Orinoco rivers and eventually the ocean could explain the increased growth of the belt on the western side. Parsons said warming waters likely help the seaweed grow faster. Changes in wind patterns, sea currents, rainfall and drought could also affect blooms.
“It may be the entire belt is fed more some years than others by dust that contains iron and other nutrients that comes from the Sahara Desert,” said Lumpkin, of NOAA.
It’s not clear whether climate change is playing any part. Hu said extreme weather that is happening more frequently due to climate change — high wind events, storms, more precipitation — could be a contributor.
Is it harmful to humans?
It can be. When sargassum decomposes, it releases ammonia and hydrogen sulfide, which accounts for the rotten-egg stench. Brief exposure isn’t enough to make people sick, but prolonged exposure — especially for those with respiratory issues — can be dangerous, scientists say.
Hu said it could be an issue for hotel workers and others who may spend hours removing the decomposing sargassum from beaches.
Left to rot on the beach, sargassum can turn into a problem. It can harm coastal marine ecosystems and also supports the growth of fecal bacteria.
Environmental reporting for WGCU is funded in part by VoLo Foundation, a non-profit with a mission to accelerate change and global impact by supporting science-based climate solutions, enhancing education, and improving health.
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