A record amount of seaweed is smothering Caribbean coasts from Puerto Rico to Barbados as tons of brown algae kills wildlife, chokes the tourism industry and releases toxic gas.
More than 24 million tonnes of sargassum blanketed the Atlantic in June, up from 18.8 million tonnes in May, according to a monthly report published by the University of South Florida's Optical Oceanography Lab that noted "a new historical record."
July saw no decrease of algae in the Caribbean Sea, said Chuanmin Hu, an optical oceanography professor who helps produce the reports.
"I was scared," he recalled feeling when he saw the historic number for June.
He noted it was 20 per cent higher than the previous record set in May 2018.
Mr Hu compiled additional data for The Associated Press that showed sargassum levels for the eastern Caribbean at a near record high this year, second only to those reported in July 2018.
Levels in the northern Caribbean are at their third highest, following July 2018 and July 2021, he said.
Scientists said more research was needed to determine why sargassum levels in the region are reaching new highs, but the United Nations' Caribbean Environment Program said possible factors included a rise in water temperatures as a result of climate change and nitrogen-laden fertilisers and sewage waste fuelling algae blooms.
"This year has been the worst year on record," said Lisa Krimsky, a researcher and faculty member with Florida Sea Grant and a water resources regional specialised agent at University of Florida.
"It is absolutely devastating for the region."
She said large masses of seaweed have a severe environmental impact.
Decaying algae has been altering water temperatures and the pH balance, as well as leading to declines in seagrass, coral reef and sponge populations.
"They're essentially being smothered out," Ms Krimsky said.
Wave of algae poses risk to people
The "golden tide" has also hit humans hard.
The concentration of algae has become so heavy in some parts of the eastern Caribbean that the French island of Guadeloupe issued a health alert in late July.
It warned some communities about high levels of hydrogen sulfide emanating from huge rotting clumps of seaweed, which can affect people with respiratory problems including asthma.
The Biden administration declared a federal emergency after the US Virgin Islands warned last month of "unusually high amounts" of sargassum affecting water production at a desalination plant near St Croix.
The plant was already struggling to meet demand amid an ongoing drought.
"We're consuming as much as we can produce right now," said director of the islands' emergency management agency Daryl Jaschen.
"We're very concerned about that."
The US Virgin Island's electricity generating station also relies on ultra-pure water from the desalination plant to reduce emissions monitored by the US Environmental Protection Agency.
The loss of such water would force the government to use a type of diesel fuel that was more expensive and in limited supply, officials said.
Industries grind to a halt
Sargassum in moderation helps purify water, absorb carbon dioxide and is a key habitat for fish, turtles and crabs.
But it is bad for tourism, the economy and the environment when too much accumulates just offshore or on beaches.
A carpet of brown algae recently surrounded an uninhabited island near the French Caribbean territory of St. Martin that was popular with tourists, forcing officials to suspend ferry services and cancel kayaking and snorkelling tours.
The normally translucent waters around Pinel Island turned into a prickly brown slush.
"This is the worst we've ever seen it for sure," said Melody Rouveure, general manager for a tour company in the area.
"It did ruin my personal beach plans."
On Union Island, which is part of St Vincent and the Grenadines, the seaweed invasion has forced some resorts to close for up to five months in the past.
Masses of sargassum also have strangled the Caribbean's fishing industry.
It damages boat engines and fishing gear, prevents fishermen from reaching their boats and fishing areas and leads to a drop in the number of fish caught.
Barbados had been especially hit hard since flying fish make up 60 per cent of the island's annual landed catch, according to the University of the West Indies.
An overabundance of sargassum was blamed for the recent deaths of thousands of fish at the French Caribbean island of Martinique.
It also had activists concerned about the plight of endangered turtles, with some dying at sea entangled in seaweed or unable to lay their eggs given the mat of algae covering the sand.
In the Cayman Islands, a thick carpet of sargassum prompted officials to launch a trial program in which crews pumped more than 2,880 square feet (268 square meters) of seaweed out of the water.
But on Tuesday, the government announced it had suspended removal efforts because the level of decomposition made it impractical.
"The sargassum stranding in the North Sound is unlike any we have experienced previously in terms of its location, weather conditions and scale," officials said.
Other island nations have opted to use heavy machinery to remove seaweed from the beach, but scientists warned it would lead to erosion and could destroy the nests of endangered turtles.
ABC/AP
