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FL - FGCU Professor explains Sargassum Seaweed Blob in the Atlantic Ocean

ESTERO, Fla. — As we battle red tide, many are now looking to the future as there are reports of tons of seaweed approaching Florida's coastline. The great Atlantic sargassum belt naturally occurs every year, but this year some claim the seaweed will overtake beaches in Florida.

"Everyone is thinking, Blob, like the movie, that's going to come and swallow up,” said FGCU’s Water School’s Dr. Barry Rosen. “It's a floating seaweed."

Dr. Rosen specializes in aquatic biology and harmful algal blooms. He says that sargassum can cause minor issues, but it doesn’t create any toxins like other algal blooms, such as blue-green algae or red tide.

“This is the only time it becomes a nuance — that is the difference between a harmful algal bloom and a nuance bloom — when it can build up on a beach and start to decay,” said Dr. Rosen.

And if it builds up along the coast, sargassum can smother coral reefs, alter the pH of water, and has the potential to choke local economies by closing tourism sites, cutting off marinas, and constricting fishing yields. But the open sea is still a critical habitat for a variety of fish and wildlife. It also creates a ton of oxygen via photosynthesis.

“All algae produce oxygen,” said Dr. Rosen. “It’s part of what they do. Without it…50% of the Earth that’s where our oxygen comes from algae, including this seaweed.”

In February, sargassum was recorded as the second-highest abundance for the month, but in recent satellite data from NASA, the bloom appears to have slightly decreased. And the question we all want to know... “Is it going to come to our shore? We really don’t know that,” said Dr. Rosen.

Dr. Rosen says Southwest Florida residents should be more focused on the current red tide versus the potential sargassum seaweed washing up on the beach.

“Right now, we have red tide. That’s not a wait-and-see — it’s here. To me, that is a much more important issue. And certainly, it’s real now,” said Dr. Rosen.

“We don’t know what sargassum is going to do,” said Dr. Rosen. “We don’t know which way it is going to drift. And it’s going to have to drift, it is planktonic. It’s going to drift — move with the currents.”

Dr. Rosen says it is completely possible that sargassum doesn’t even reach the Southwest Florida coastline. And if it does reach here in the near future, it would compete with the red tide for nutrients and release its own set of compounds that red tide wouldn’t like. The combination would likely decrease our current red tide predicament.

The University of South Florida released a forecast for the sargassum at the beginning of the month, presenting a glimmer of hope for the 2023 bloom. It may not be as large as previously seen. That said they are still predicting a major sargassum year. USF forecasts sargassum to increase in the Caribbean Sea and the Gulf of Mexico over the next few months.

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