Seaweed pollution along Miami Beach, Florida — Courtesy: Shutterstock — Sergii Figurnyi
According to Florida scientists, they have discovered a “tipping point” in the Atlantic Ocean’s meteorological conditions that led to massive clumps of toxic seaweed flooding Caribbean beaches in recent summers.
A surplus of nutrients in the water, such as nitrogen and phosphorus from runoff from intensive farming and carried into the ocean in the Congo, Amazon, and Mississippi rivers, has been proposed as the cause of the Great Atlantic Sargassum Belt, which has killed marine life, damaged human health, and plagued the travel and tourism sector in a number of nations.
The University of South Florida (USF) marine scientists admit that this is a contributing factor, but they claim that the main source of nutrients is a seasonal phenomenon called vertical mixing, whereby shifting winds stir the ocean and bring deepwater nutrient concentrations to the surface.
Changes in circulation and wind patterns drove more sargassum into the warmer waters of the tropics, where it grew through photosynthesis into the massive blooms that eventually ended up on the Caribbean and US Gulf coast beaches. They identified changes in atmospheric pressure over the Atlantic starting around 2009 as the tipping point.
Frank Muller-Karger, a distinguished professor and biological oceanographer at USF’s College of Marine Science, described the outcome as unexpected. In order to mimic the movement of blooms on powerful currents regulated by negative North Atlantic oscillation (NAO) and how shifting atmospheric conditions contributed to the formation of the gigantic sargassum belt, his team of researchers from around the world employed computer modeling.
We previously proposed the theory that the sargassum blooms in the tropical Atlantic are not fueled by rivers. The hypothesis that the blooms are fed by nutrients from the ocean’s somewhat deeper layers is supported by this model.
“Models indicated that certain seaweed patches were carried by the wind and currents from the Sargasso Sea toward Europe, then moved southward, and from there were injected into the tropical Atlantic,” Muller-Karger added.
Initially, we saw that the NAO was pushing a small number of patches south. However, the ideal conditions were present for these algal patches to develop and continue to thrive. Due to adequate light, nutrients, and warmer temperatures, this population of algae—which is now isolated from the Sargasso Sea—forms new blooms each year, he said.
Giant clumps of goop from the 5,000-mile-wide sargassum belt have been washing up on the Caribbean coast and from Florida to Mexico almost yearly for over ten years, causing issues for local government agencies and tourism-related enterprises.
There are serious health issues as well. Large amounts of hydrogen sulfide are released by the decomposing sargassum, giving the air a rotten egg-like stench and potentially triggering asthma and other respiratory conditions.
Researchers at Florida Atlantic University (FAU) discovered large concentrations of the flesh-eating Vibrio bacterium hiding in the decaying vegetation in 2023, prompting them to warn of a “perfect pathogen storm [with] implications for both marine life and public health.”
They said that when plastic waste from ocean pollution combined with sargassum, the germs multiplied, posing a further health concern to visitors, city workers removing the seaweed, and volunteers cleaning up the beaches.
According to Tracy Mincer, assistant professor of biology at FAU’s Harbor Branch Oceanographic Institute and Harriet L. Wilkes Honors College, “these Vibrio are very aggressive and can find and stick to plastic within minutes.”
“We are committed to raising public awareness of these related hazards. Specifically, until the hazards are further investigated, care should be taken when harvesting and processing sargassum biomass.
Nature Communications published the USF study, which was conducted in partnership with researchers from the Center for Scientific Research and Higher Education, the University of Toulouse, and the Sorbonne University.
In order to model the annual blooms, their analysis examined decades’ worth of wind, currents, and three-dimensional nutrient observations from the Atlantic.
Stories that matter are our priority. At Florida Insider, we make sure that the information we provide our readers is accurate, easy-to-read, and informative. Whether you are interested in business, education, government, history, sports, real estate, nature or travel: we have something for everyone. Follow along for the best stories in the Sunshine State.
Chris began his writing as a hobby while attending Florida Southern College in Lakeland, Florida. Today he and his wife live in the Orlando area with their three children and dog.
