Tons of brown, stinky seaweed washing up on the Space Coast. Get ready for more

Jim Waymer
Florida Today

While vital seagrass vanishes in coastal waters statewide, the Caribbean Sea keeps on gifting Central Florida's beaches mounds of mushy, stinky golden brown seaweed. And researchers warn that this so-called Sargassum storm is likely to get worse before it gets better.

Fed by sewage and fertilizers in Brazil and thereabouts, the seaweed is expected to keep coming all summer long. Oceanographers expect the Sargassum to thicken on beaches from the eastern Caribbean throughout Florida's east coast from now until July at least, but possiblythrough September.

Florida Atlantic University's Harbor Branch Oceanographic Institute released a study Monday that suggests increased availability of nitrogen from natural and man-made sources, including sewage, fuels excess Sargassum growth. According to the release, our waste can turn a critical nursery habitat into toxic algae dead zones, "with catastrophic impacts on coastal ecosystems, economies, and human health." 

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"Over its broad distribution, the newly-formed Great Atlantic Sargassum Belt can be supported by nitrogen and phosphorus inputs from a variety of sources including discharges from the Congo, Amazon and Mississippi rivers, upwelling off the coast of Africa, vertical mixing, equatorial upwelling, atmospheric deposition from Saharan dust, and biomass burning of vegetation in central and South Africa,” Brian Lapointe, senior author on the paper and a research professor at FAU Harbor Branch, said in Monday's release. 

Sargasso Sea

Sargassum is a constant presence in the Atlantic, so much so that a large swath of the North Atlantic is known as the Sargasso Sea. In past years, the weed has nagged fishermen from the Caribbean to Massachusetts, forcing them out of certain areas after they kept reeling in clumps of the stuff.

It typically drifts in long lines near the Gulf Stream and provides vital food for young sea turtles. Experts say sustained winds, combined with seasonal shifts in the Gulf Stream, are responsible for the sudden overabundance on local beaches.

Most of Cocoa Beach's wrack line — that zone of the beach where seaweed and other debris is deposited at high tide — has been almost completely Sargassum for a week now.

The recent stringy mess on Brevard County beaches hearkens back to the widespread Sargassum algae blooms that hit county beaches in 2014 and 2015. Huge Sargassum blooms blanketed beaches along the east coast of Barbados and Puerto Rico in 2014, as well.

It seems now that extreme blooms appear on an almost yearly basis.

The FAU researchers used unique historical baseline seaweed tissue from the 1980s to compare its chemical makeup to samples collected since 2010. They found dramatic changes in the chemistry and composition of Sargassum weed since the 1980s, "transforming this vibrant living organism into a toxic “dead zone,” FAU's announcement said.

Their findings were published in Nature Communications.

Biologists say the vegetation washing up on the Space Coast and shorelines statewide this week usually is beneficial to the beach. It provides food for birds, crabs and other wildlife and habitat for hiding. So raking the stuff off the beach can be controversial, often pitting tourism against conservation interests.

But when the weed feeds off too much sewage, it can turn toxic for some wildlife, FAU and other research shows.

Sargassum blooms ramping up

USF three years ago began putting out the monthly outlook bulletins on blooms of the weed.

Sargassum blooms tend to ramp up in April and start to decrease from late August to September.

From March to April, alone, transport of Sargassum weed from the Caribbean Sea to Florida increased from 10.1 million tons in March to 10.6 million tons, according to the most recent outlook bulletin for the seaweed by the University of South Florida's Optical Oceanography Lab outlook bulletin. That's a 5% jump and second only to April 2018, which saw a record 12.6 million tons, the bulletin said.

And USF expects the stringy things to get worse, a least through July. 

"This situation may continue into summer, and the overall bloom intensity is likely to be higher than in 2019," the bulletin said. 

In all regions combined, the total Sargassum amount grew to 12.7 million metric tons in June 2020, according to USF, lower than June 2018 (20.4 million metric tons), but higher than June 2015 (9.9 million metric tons ) and June 2019 (9.5 million metric tons).

Last year in June, satellites showed total Sargassum coverage of 920 square kilometers, compared with a historical mean of 200 square kilometers between 2011 and 2017, according to USF.

Another extreme Sargassum bloom harmed fisheries and tourism in the Caribbean in 2011.

In July 2015, thick globs of dark-brown, rancid Sargassum fouled the air and blanketed large swaths of beach near Jetty Park in Cape Canaveral. 

In January 2018, satellites spied unusually high amounts of Sargassum weed in the Caribbean and in the central West Atlantic. Then early February 2018, USF's Optical Oceanography Lab generated and distributed its first 1-page Sargassum outlook bulletin for the Caribbean Sea, and predicted that 2018 would be a major bloom year for the Caribbean.

“Considering the negative effects that the Great Atlantic Sargassum Belt is having on the coastal communities of Africa, the Caribbean, Gulf of Mexico and South Florida, more research is urgently needed to better inform societal decision-making regarding mitigation and adaptation of the various terrestrial, oceanic, and atmospheric drivers of the Sargassum blooms,” Lapointe said.

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Jim Waymer is environment reporter at FLORIDA TODAY.

Contact Waymer at 321-242-3663                                         

or jwaymer@floridatoday.com.

Twitter: @JWayEnviro

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