By Mike S Payton, Contributing Reporter

MIAMI BEACH, FLORIDA – NASA reported yesterday, July 8th, that an unprecedented belt of brown algae stretches from West Africa to the Gulf of Mexico. Last night the City of Miami Beach also shared a Sargassum Frequently Asked Questions document from the Florida Department of Health (FDOH).

Sargassum seaweed off Big Pine Key in the lower Florida Keys, Miami Beach, Miami, Florida, News
An unhealthy amount of Sargassum off Big Pine Key in the lower Florida Keys, photo by Brian Lapointe.

The NASA report explains that scientists at the University of South Florida in St. Petersburg’s College of Marine Science used NASA satellite observations to discover and document the largest bloom of macroalgae in the world, dubbed the Great Atlantic Sargassum Belt.

“The scale of these blooms is truly enormous, making global satellite imagery a good tool for detecting and tracking their dynamics through time,” said Woody Turner, manager of the Ecological Forecasting Program at NASA Headquarters in Washington.

Based on computer simulations, they confirmed that this belt of the brown macroalgae Sargassum forms its shape in response to ocean currents. It can grow so large that it blankets the surface of the tropical Atlantic Ocean from the west coast of Africa to the Gulf of Mexico.

In 2018, more than 20 million tons of it floated in surface waters and became a problem to shorelines lining the tropical Atlantic, Caribbean Sea, Gulf of Mexico, and east coast of Florida, as it carpeted popular beach destinations and crowded coastal waters.

Before 2011, most of the free floating Sargassum in the ocean was primarily found in patches around the Gulf of Mexico and Sargasso Sea. The Sargasso Sea is located on the western edge of the central Atlantic Ocean and named after its popular algal resident.

The Great Atlantic Sargassum Belt in July 2018, Miami Beach, Miami, Florida, News
The Great Atlantic Sargassum Belt in July 2018, image provided by NASA/Earth Observatory.

In patchy doses in the open ocean, Sargassum contributes to ocean health by providing habitat for turtles, crabs, fish, and birds and, like other plants, producing oxygen via photosynthesis. But too much of this seaweed can crowd out marine species, especially near the coast.

In 2011, Sargassum populations started to explode in places it hadn’t been before, like the central Atlantic Ocean, and then it arrived in a massive scale that suffocated shorelines and introduced a new nuisance for local environments and economies.

Chuanmin Hu of the USF College of Marine Science, who led the research, has studied Sargassum using satellites since 2006. “The ocean’s chemistry must have changed in order for the blooms to get so out of hand,” Hu said.

Sargassum reproduces from fragments of the parent plant, and it probably has several initiation zones around the Atlantic Ocean. It grows faster when nutrient conditions are favorable, and when its internal clock ticks in favor of reproduction.

“This is all ultimately related to climate change, as climate affects precipitation and ocean circulation and even human activities [that can lead to Sargassum blooms], but what we’ve shown is that these blooms do not occur because of increased water temperature,” Hu said. “They are probably here to stay.”

Due to the influx of seaweed on the beaches in many areas of the country and around the Caribbean, the City of Miami Beach continues to work closely with Miami-Dade County as they work on ways to mitigate the seaweed in Miami Beach.

The Florida Department of Health has issued these frequently asked questions (FAQ) regarding Sargassum. The FAQ says, “This amount of Sargassum on beaches concern people living and working on or near the beach, because rotting Sargassum produces hydrogen sulfide gas which is unpleasant to smell.”

Adding, “Because small organisms like jellyfish larvae can live in seaweed, some people have also experienced skin rashes and blisters from the organisms living in the seaweed.”


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