The massive 5,000-mile-long seaweed swath that has been creeping westward across the Atlantic just broke a record in the Caribbean. That does not bode well for Florida. The mass will continue to drift toward the Gulf Stream, which will continue to carry piles of the seaweed to Sunshine State beaches.
Bands of the seaweed have been reaching South Florida already this season. March saw a surge swamping the Keys.
The Great Atlantic Sargassum Belt, as scientists have dubbed it, increased in volume in most regions of the Atlantic, according to the University of South Florida’s monthly sargassum report, and set a record for the most seaweed ever recorded for the month of April in the Caribbean region.
Researchers estimated a record of 3 million tons of sargassum in the Caribbean Sea in April, with build-ups along southern coasts of Hispanola, Jamaica, and Puerto Rico.
The floating seaweed in the Caribbean will not only clog beaches there, but will drift westward into the Gulf of Mexico, where the Gulf Stream will deliver sprawling mats of macroalgae to Florida’s east coast beaches.
The satellite images showed the belt moving slightly west from March to April of this year, and growing more dense off the Yucatan Peninsula. That buildup is key for Florida — the Loop Current, which pushes north between Cuba and the Yucatan Peninsula, carries the seaweed into the Gulf, where the images show aggregations. From there, it can head to Florida.
The enormous swath of tendrilled, somewhat rubbery seaweed is a natural annual occurrence, but it has surged in the last decade. Though not particularly pungent on the open ocean, and home to myriad sea life, when the mats of macroalgae pile up and decompose on the beach or along mangrove shorelines, they release hydrogen sulfide gas, which has an odor reminiscent of rotten eggs, and can cause respiratory problems.
According to a 2019 paper by scientists at the University of South Florida, annual sargassum blooms, which typically start far out in the Atlantic in spring and move westward, saw a surge in 2011, and have continued to increase since then.
Why the seaweed surge? Oceanographic researcher Brian Lapointe of Florida Atlantic University said the sargassum zone has shifted from the Sargasso Sea, a massive area of the Atlantic off the U.S. southern seaboard, south to tropical waters. The warm waters may help explain the growth.
Another possible boost to the bloom on its new southern route is the plume of water from the Amazon River, which Lapointe said is essentially a nutrient bomb due to flooding and extreme runoff from the Amazon Basin exacerbated by deforestation and farming practices.
June is typically the peak month of coverage oceanwide, according to satellite images analyzed by scientists, but that coverage takes time to reach the U.S.
“Looking ahead,” said the April report, “the total Sargassum quantity is expected to increase over the next few months, with impacts of beaching events in the CS and GoM worsening accordingly.”
