Beaches beware: Giant bloom of sargassum seaweed reaches record-high level
Florida, Mexico and Caribbean brace for incoming 8,000-km-wide seaweed blanket
An over 8,000-kilometre-wide brown glob of seaweed, known as the Great Atlantic Sargassum Belt, is on the move and could potentially wreak havoc on beaches in Florida, Mexico and the Caribbean this summer.
The slimy, smelly mats of unsightly seaweed crowding beaches in Florida, Mexico and the Caribbean are already overwhelming picturesque tourist destinations — and it is likely to get even worse.
The Great Atlantic Sargassum Belt, an 8,000-kilometre-wide brown mass of blanketed seaweed, has reached a record-high volume for the month of March. According to the University of South Florida’s Optical Oceanography Lab, about 13 million tons of sargassum — a form of macroalgae — was observed via satellite spanning from the Gulf of Mexico to the west coast of Africa.
The historical levels of sargassum identified in March will cause “inevitable” major beaching events around the Caribbean, the ocean side of the Florida Keys and the east coast of Florida, researchers said. The exact timing and location of washed-up sargassum is difficult to determine as it relies on the tide and wind in the region.
Only a fraction of the 13 million tons of sargassum in the Atlantic will wash up on beaches this year, though large swaths of the macroalgae have already made landfall.
The amount of sargassum floating in the east Caribbean will reportedly continue to grow as it migrates westward toward the Gulf of Mexico. The sargassum growth will peak in either June or July, though there is already evidence to suggest it will be the largest bloom ever recorded.
The volume of sargassum was apparently smaller than expected in February, but the University of South Florida team said this was determined to be a result of “persistent cloud cover” in the eastern Atlantic.
In open waters, sargassum is mostly harmless and serves as a reliable habitat for ocean life. When it washes up on shore, however, not only is sargassum unsightly, but it also reeks and worsens air quality as it decomposes.
As sargassum piles up and rots on beaches in Florida, Mexico and the Caribbean, it releases toxic hydrogen sulphide into the air — a gas that smells of rotten eggs and may cause respiratory and neurological issues in humans. Sargassum can also smother mangrove habitats, reduce oxygen levels in water, impact critical infrastructure and stifle coastal tourism.
It is not yet known exactly why or how the sargassum appears to be growing year after year, though the climate crisis is a probable cause. The New York Times reported that sargassum growth is likely seasonal and has to do with the discharge of fertilizer runoff into major waterways in the Congo, Amazon and Mississippi rivers. Fossil fuel emissions and carbon monoxide released as a result of deforestation may also contribute to the blanket’s growth.
Removing sargassum from beaches requires ample manpower and can be costly. The problem, however, is not just cleanup — even when sargassum is collected from beaches, the question of what to do with the seaweed remains.
Though some scientists have suggested using sargassum as fertilizer, this may be dangerous as sargassum contains arsenic, which could infiltrate the food chain. Composting sargassum would result in the same dilemma: arsenic potentially leeching into groundwater sources. Processing the minerals in sargassum is not cost-effective.
