When waves of sargassum – a type of seaweed – washed up on Eastern Caribbean shores seven years ago, people hoped it was a one-off. Matted piles swamped coastlines from Tobago to Anguilla.Three years later the seaweed returned, in larger quantities.
Now it is happening again and everything suggests 2018 could be the worst year yet.”On satellite images the quantity that’s being picked up is greater than ever before,” says Prof Oxenford, who is based in Barbados.
“Certainly we’ve had it for longer and in huge amounts. And some of the islands are getting it for the first time.”
Caribbean governments are acknowledging that the seaweed, which impacts on tourism, fisheries and wildlife, could pose a long-term threat.”The same way we prepare for hurricanes, we have to prepare for sargassum,” Antigua’s environment minister said recently.
On shore, as well as blocking beaches and repelling swimmers, the sargassum stinks as it decomposes.
Removal is time-consuming, expensive and can damage the beaches. Incoming rafts smother sea grasses and coral reefs, while fishermen struggle to get in the water.”The sargassum tangles up their motors, their engines, their nets, their lines,” says Ms Monnereau.Then there is tourism. In one extreme case, a resort in Antigua was forced to close its doors until 30 September.
“The issue is that we never know what it’s going to be like – we can have a week or two weeks where it’s very clear and then all of a sudden overnight it washes in,” says Larry Basham of Elite Island Resorts, which runs St James’s Club.
“We’ve spent an ungodly amount of money on tractors, heavy equipment, we’ve tried a number of different barrier systems on the water, none of which has worked well. The sargassum is mostly affecting southern and eastern coasts and in the Eastern Caribbean, many of the main tourist beaches face west.
The reason southern and eastern shores are worst hit lies in the seaweed’s source. In 2011 people initially assumed the Caribbean influx had, for some reason, drifted from its traditional home in the Sargasso Sea.But now research indicates the sargassum is from a new source – an oval band stretching from the Brazilian coast to West Africa.
James Franks, of the University of Southern Mississippi’s Gulf Coast Research Laboratory says the sargassum circulates through this band, consolidates off Brazil and then is periodically released northwards by currents into the Caribbean.
But he says it is not yet clear what has caused this huge new bloom.
One major question is how long the phenomenon will continue.Satellite images from the University of South Florida’s (USF) Optical Oceanography Laboratory currently show historically high monthly levels of sargassum in the region.
“It is likely this bloom will occur until September this year,” says Dr Mengqiu Wang of USF.But it is not clear what will happen next year, or the year after. Mr Franks says prediction strategies will be very important in planning for influxes but they are in “the elementary stage of development at this point”.
