Change in giant sargassum blob offers 'glimmer of hope' but Florida could get hit in March

The Florida Keys could start seeing small amounts of sargassum this month. A scientist at FAU said he received photos March 5 from friends showing sargassum on a popular beach in Key West.

Kimberly Miller
Palm Beach Post

A massive sargassum bloom that stretches from near the coast of Africa through the Caribbean Sea and into the Gulf of Mexico has decreased in volume compared to its January girth, offering a "glimmer of hope" that it won't be the monster record-breaker scientists originally thought.

But the 6.1 million tons of seaweed surging west is still the second highest amount recorded for February, according to a monthly sargassum monitoring report from the University of South Florida.

USF oceanography professor Chuanmin Hu said in the report that it's unusual to see a decrease in the overall amount of sargassum from January to February but that it has happened one other time on record, in 2019.

'Daring' coral rescue as officials attempt to safeguard genetics of Florida reef tract

A giant sargassum seaweed blob takes aim at Florida

Spring Break 2023:Is red tide on the east coast of Florida?

Where is the seaweed headed in Florida?

"Looking ahead, the decrease in sargassum quantity is uncommon, and presents a glimmer of hope that the overall 2023 bloom may not be as large as previously feared, although 2023 will still be a major sargassum year," Hu said.

And although the overall amount is down from the 8.7 million tons measured in January, its migration west has doubled the amount in the Caribbean Sea with "notable amounts" reaching the Yucatan Peninsula near mid-February and small amounts observed in the Gulf of Mexico.

Sargassum piles up in the ocean and on the beach next to the Boynton Inlet jetty in August 2019.

Hu said the Florida Keys could start seeing small amounts of sargassum this month. Florida Atlantic University research professor and algae expert Brian LaPointe said he received photos March 5 from friends showing sargassum on Smathers Beach in Key West.

"So, we are already seeing the tip of the iceberg," said LaPointe, noting that the belt as of early March was 5,000 miles long and 200 to 300 miles wide.

Seaweed is guided by currents, winds and storms. If it gets into the Gulf Stream current that comes closest along the east coast to Palm Beach County, it could reach the beach in huge quantities on an east wind.

Is it safe to swim in sargassum?

Sargassum is a lifeline for fish nurseries, hungry migratory birds and sea turtle hatchlings seeking shelter in its buoyant saltwater blooms. But in mass quantities, it chokes life from canals, clogs boat propellers and is a killjoy at the beach, piling up several feet deep like a rotting bog emitting hydrogen sulfide as it decomposes.

It's generally safe to swim in, but can turn the water an uninviting brown and be uncomfortable when it scratches against your skin

Satellite image of sargassum bloom in February 2023. The deeper reds and oranges indicate higher amounts.

What is the seaweed season in Florida?

Last year was a record-breaker for the total amount of sargassum, with it reaching a peak of 22 million tons in July. Hu said 2023 will be another major sargassum year, possibly surpassing 2022.

Seaweed is usually at its highest quantity in the summer and early fall months. During summer, predominant easterly sea breezes can push it to shore. But there have been when the seaweed hit Florida beaches during tourism season.

It's too early to know how much seaweed will reach Florida's beaches, but it has shown up in varying degrees and depths during every major growth year, hitching a ride on the loop current to assail the Keys and areas north from Miami to Jacksonville.

5 things to know about Jetty's restaurant in Jupiter after sale

Red tide impacting Florida beaches:6 things you need to know about toxic algae

More:World's largest sargassum bloom and why it's here to stay

Hu's Optical Oceanography lab at USF measures the sargassum by satellite and has images dating back decades. He was part of a team of scientists that discovered the world's largest sargassum bloom in the Atlantic Ocean, dubbing it the Great Atlantic Sargassum belt.

What causes sargassum on the beach?

A 2019 report on the group's findings pointed to two main culprits for the increase in sargassum ― higher nutrient levels in runoff from the Amazon River and when an upwelling in the eastern Atlantic brings cooler water and nutrients from the bottom of the ocean to the surface. Higher rainfall amounts caused by a warmer climate can also mean more runoff from other rivers to feed the bloom, including the Mississippi River and Orinoco River in South America.

A University of Miami study also released in 2019 found that smoke from African fires ― either from those burning wild or burning to clear land ― has phosphorus in it that could also be feeding thesargassum after it settles out of the atmosphere.

Kimberly Miller is a veteran journalist for The Palm Beach Post, part of the USA Today Network of Florida. She covers real estate and how growth affects South Florida's environment. Subscribe to The Dirt for a weekly real estate roundup. If you have news tips, please send them to kmiller@pbpost.com. Help support our local journalism, subscribe today.