NEW HAVEN, Conn. (WTNH) – Marine and research scientists are tracking a 5,000-mile-wide seaweed bloom that has been heading toward beaches in Florida, threatening marine life and beach vacationers.

Within the last decade, scientists have noticed that these large patches of seaweed, known as sargassum have been reaching closer to shore. Historically, sargassum has been a part of the ocean as far back as we have records, yet nobody has seen much of it on shore. Now, this seaweed bloom is believed to be one of the largest in history — currently spanning twice the width of the United States.

“It’s like a forest on the surface of the ocean,” said Peter Auster, a senior research scientist with the Mystic Aquarium.

Auster has researched fish communities that live in sargassum for many years. According to his research, many fish, sea turtles and marine mammals rely on sargassum to live. However, as this seaweed reaches closer to land, it creates a problem for beaches.

“The problem with this coming ashore obviously is the effect on beaches.” Auster said. “If it begins to decay rapidly, it produces an obnoxious gas that can make people ill.”

When sargassum rots, it produces hydrogen sulfide, which can cause respiratory problems and intense odors that drive away avid beachgoers.

“If you get a big mass of this stuff on the beach, it’s like what you’d think about if you had a whole hen house full of rotting eggs,” Auster said. “Not pretty.” 

Brian LaPointe, a research professor at Florida Atlantic University’s Harbor Branch Oceanographic Institute has been studying blooms for decades.

“Following the big 2018 blooms, doctors in Martinique and Guadeloupe reported thousands of people going to clinics with breathing complications from the air that was coming off these rotting piles of sargassum,” LaPointe said.

Not only are these large chunks of seaweed unpleasant to see or breathe in, but they can also prohibit boats from passing through the water.

“Even if it’s just out in coastal waters, it can block intake valves for things like power plants or desalination plants, marinas can get completely inundated and boats can’t navigate through,” Brian Barnes, an assistant research professor at the University of South Florida’s College of Marine Science told NBC News. “It can really threaten critical infrastructure.”

As temperatures rise with global warming, scientists believe the warmer ocean waters are the main cause for the growth in sargassum.

“This is kind of part of our warming planet and part of the continuing effects of human activities in terms of turn off of nutrients that fuel the production of these plants,” Auster said.

Plus, urban and agriculture runoff is sending nitrates from fertilizers and other nutrients flowing into the ocean, which is helping to feed the bloom.

While the bloom is headed toward the the Florida Gulf Coast now, Auster said it’s not impossible for it to reach further north as time goes on.

“It could certainly move up the coast with the gulf stream and with warming waters,” Auster said. “But a number of circumstances would have to fall into place for this to end up in the Long Island Sound.” 

The Associated Press contributed to this report.