Some of Florida’s most popular beaches could be in for a one-two punch of trouble as thousands of spring breakers flock to the Sunshine State. 

A toxic algae bloom known as red tide is already killing fish along the Gulf Coast, causing a stench. Now, a massive blob of seaweed twice as wide as the United States is drifting across the Atlantic and could wash ashore in the coming weeks, creating an even bigger mess.

“It could be two problems turning into a bigger one,” said Mike Parsons, a marine science professor at Florida Gulf Coast University.

The algae bloom has essentially choked some sea life, producing a foul smell as dead marine animals wash ashore. 

It’s not the only effect. The ocean breeze can carry a toxin released by the red tide algae ashore, which can cause health problems for people including coughing, irritated throat and itchy eyes, as well as difficulty breathing and asthma attacks.

The algae occurs naturally. But professor Parsons and a team from the water school at Florida Gulf Coast University are looking into whether pollution is making the blooms worse.

Bad red tides have occurred in the past, Parsons said, including in the 1940s, 50s and 60s. 

“The big concern is: now that our coastlines are more developed and there’s a lot more people in Florida than there used to be, how are we affecting water quality and how is that affecting red tide?” he said. 

“There is evidence that we are influencing red tide through discharges,” he said. “Any of the nutrients that get into our water bodies – Lake Okeechobee, Caloosahatchee, other rivers – those nutrients can come down into the coastal waters of the Gulf of Mexico, and they may be feeding red tide.”

In other words, while pollution is “definitely” not the cause of the problem, according to Parsons, “it may be aggravating the problem.” 

Red tide originates dozens of miles offshore when there are high amounts of the algae known as Karenia brevis. Parsons said that based off of data his team has collected, the belief is that red tide sits in deep water, then rises to the surface after moving inshore, where it becomes concentrated and causes a traffic jam at the coastline. 

Red tide can have an impact on tourism, as businesses along the Gulf Coast are still recovering from Hurricane Ian last year. But a lingering stench didn’t stop some tourists recently, like Melanie Coulter of Wisconsin, whose vacation ended up including a snapshot of a dead horseshoe crab. 

“As we were walking from our car, I thought, ‘Oh what’s that stench,’ but then once you get on the beach the wind makes it not so bad,” Coulter said.

Parsons advises beachgoers to leave a stretch of beach where they see dead fish, or start getting a scratchy nose or watery eyes. 

“But the good news is that red tide is really patchy, so you can probably just move a couple miles down the beach and find a perfectly clean, safe area to be,” he said.

Still, another problem now looms: a 5,000-mile-wide patchwork of seaweed clumps in the Atlantic that is making its way toward the Caribbean and Mexico – and Florida beaches.

The mass is known as sargassum, a brown seaweed that floats in large masses, according to the National Oceanic and Atmospheric Administration.

“There are really big blooms of sargassum out there right now,” Parsons said. “They’ve been washing up on beaches in the Caribbean, in Miami, and it looks like it’s our turn now. And that’s not going to be a positive thing.”

As the biomass degrades, it releases gases like hydrogen sulfide, which smells like rotten eggs and is harmful, he said.

Li Cohen and Caitlin O’Kane contributed to this article.