Researchers at the University of South Florida discovered a steep decline in sargassum, a brown seaweed found in large floating masses, despite huge swaths of it inundating beaches in Florida and beyond.
Researchers say high temperatures in the Gulf of Mexico may be to blame.
After analyzing satellite data, researchers found the smelly seaweed had steep population declines in the Gulf and the north Sargasso Sea.
Researchers have called it “fascinating” how the tropical Atlantic has seen an increase in sargassum over the past decade, but at the same time, the Sargasso Sea has seen a significant decrease in sargassum compared to its historical levels.
When sargassum washes ashore and decays, it emits foul odors and disrupts coastal communities.
But while it’s in the water, USF College of Marine Science assistant research professor Brian Barnes says it serves as an important habitat for marine life.
“Just like we talk about deforestation and we talked about the, you know, losing rainforests in the Amazon and so forth. You know, this habitat has been called the rainforest of the sea. And we are losing it,” Barnes told WMNF.
Barnes said record high temperatures in the Gulf likely play a role in the decline.
“As we’ve seen that increase in one specific area of the Atlantic Ocean, there’s been a decrease in the kind of historical footprint for sargassum. So one area is seeing a huge bloom, and other areas, essentially, sargassum has declined dramatically,” Barnes said.
While sargassum in the Gulf prefers temperatures between 68 to 82 degrees Fahrenheit, summer water temperatures in the Gulf have recently exceeded 86 degrees.
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This article appears in Dec. 04 – 10, 2025.