Lisa O’Carroll Fromm The Guardian UK

Proliferation of thick brown algae is affecting fishing, tourism and marine life on both sides of the Atlantic, say scientists

Saturday 17 October 2015 12.00 BST

The pristine white beaches may not be as famous as those of the Caribbean, but their unspoilt beauty makes them a haven for locals and tourists alike.

But now the shimmering coastline of Sierra Leone is being destroyed by a mysterious brown seaweed which scientists link to a similar invasion affecting beaches thousands of miles away on the other side of the Atlantic.

In some places the strong-smelling algae is piled up to two feet deep, attracting detritus and causing havoc for fishermen.

Jim Franks, a marine scientist who has been studying the phenomenon, believes it is the sargassum seaweed that normally inhabits the Sargasso sea in the north Atlantic Ocean.

Franks and his fellow researchers say this free-floating algae is now proliferating further south nearer the equator and is being swept onto the beaches on both sides of the Atlantic.

The intensity of it is causing concern; 2015 is one of the worst years we have seen
Vincent Sweeney, Unep
There have been sporadic shows of the algae in the Caribbean in the past four years, although the 2015 invasion is described by a UN official as the most “intense” yet.

Vincent Sweeney, an official with the UN Environment Programme (Unep) in Nairobi, says local rumours that the the seaweed is caused by pollution from iron ore mines are unfounded.

“This is not a localised phenomenon,” he said of the Sierra Leone bloom. “It is not as if there is a plume [of pollution] coming from a river and then seaweed grows. This is naturally occurring; it is a transatlantic phenomenon.”

Sweeney says the Unep has taken note. “It is one of the things we are considering as an emerging issue at the next UN environment assembly next May.”

“Sargassum is naturally occurring. But before 2011 this quantity has never been witnessed. It is the intensity of it right now that is causing concern; 2015 is one of the most intense years we have seen and it’s affecting tourism, marine life and fisheries,” Sweeney said.

Authorities in the Caribbean have described the outbreak as a “natural disaster” threatening the tourist-dependent economies of the picture-postcard islands.

Marine biologists are also concerned that it is affecting the marine ecosystem, particularly turtles which use the seaweed for nesting. “Young turtles cannot climb over it to get to sea,” said Sweeney. “It is also affecting fisheries. Propellors get entangled in the seaweed.”

At a conference on the issue in August, the vice chancellor of the University of the West Indies, Sir Hilary Beckles, described the invasion as the single biggest threat to tourism in the region and called for an emergency agency to be established to assist those countries in need.

Franks, a scientist with the centre for fisheries research and development at the University of Southern Mississippi, first identified the seaweed in the lesser Antilles in 2011. It was subsequently reported along the coasts of Sierra Leone, Benin and Ghana and in large mats off the shores of northern Brazil.

There are multiple theories about its cause and Franks is planning to publish a paper later this year to test his hypothesis within the wider marine science community.

“We think an increase in surface temperatures, a change in nutrients from dust from Africa may be the cause. We wish we knew more about it,” he said.

“We think there is a phenomenon of new growth in this other region. But to better understand it we need to do more about it, we need input from Sierra Leone – we need to ID the species, get an idea of how frequently it happens, what biomass is involved. These studies take time and money,” he said, appealing to the international community for help.

“The great concern is this is affecting livelihoods in very poor countries,” he added.

IMAGES:
Seaweed invasion in Tokeh Beach, Sierra Leone. Photograph: Lisa O’Carroll for the Guardian
Large quantities of seaweed blanket the beach in the Mexican resort city of Cancun, Mexico in July. Photograph: Israel Leal/AP

For more on this story go to: http://www.theguardian.com/world/2015/oct/17/seaweed-invasion-sierra-leone-caribbean