Seaweed emits poisonous hydrogen sulfide; beach closures possible

POSTED: 08/10/11 6:24 PM

Aliotti warns against sargassum health risk

MARIGOT, St. Martin – The fishermen are happy, but Vice President Pierre Aliotti called a press conference yesterday morning to alert residents and visitors about the health risks linked to the massive invasion of sargassum, a seaweed originating from the Sea of Sargasso, located between Bermuda, Florida and Puerto Rico. Coming from the north-north-west, the seaweed had landed on French-side beaches like Orient beach and also the beach in French Cul de Sac.
Aliotti said that, if the situation gets worse, he may consider closing public access to certain beaches, but for the time being the Collectivité sticks to warning people to be careful. “In the water, the seaweed is harmless, but once they land on our beaches they start to decompose. During this process they emit hydrogen sulfide. Because of the local temperatures, the seaweeds decompose and dry quickly, usually within 48 hours,” Aliotti said.
Hydrogen sulfide is a colorless, very poisonous and highly flammable gas. It spreads an unpleasant odor much like the smell of rotten eggs.
Aliotti said that inhaling the gas in small doses could trigger irritation of the eyes and the respiratory system, especially among people who are sensitive to it. The groups at risk are people with respiratory problems, asthma patients, elderly people, babies and pregnant women. Aliotti added that certain animals, especially dogs, are also sensitive to the inhalation of hydrogen sulfide.
“We are here to inform the population, and especially people who belong to the risk group, to avoid visiting beaches with a high concentration of seaweed,” Aliotti said, adding that animals are prohibited on all beaches.
The Vice-President said that the Collectivité will take all necessary measures when situations occur whereby there are so much seaweeds in the sea that the water is no longer transparent. The Réserve Naturelle advises the Collectivité about the actual situation. Possible measures are temporary bans on swimming or on visiting affected beaches.
The Collectivité considers cleaning up an area around the pier in Cul de Sac where people board a small ferry to visit Pinel Island. Orient Beach is also flooded with sargassum, especially near Mont Vernon. A clean up crew cleaned the beach last week, only to discover that the sargassum had come back with a vengeance the next day. Elsewhere on Orient Beach, restaurateurs have their hands full keeping their stretch of beach clean.
Aliotti said that the operator of the Eco-site in Grandes Cayes is prepared to receive a certain quantity of the seaweed and to turn it into compost. “Our environmental teams are on the road every day to monitor the situation,” Aliotti said.
Romain Renoux, head of the Réserve Naturelle said that his organization monitors the situation at sea. We do not have our own plane, but we do get information from pilots who fly over the area,” he said.
According to Renoux, the situation is currently “not alarming,” but he added that there is still a large patch of sargassum at sea and that it is uncertain whether this will make landfall on Saint Martin.
Cleaning up the beaches where necessary will be done “lightly” Aliotti said and not the way it was done in Martinique where cleanup crews removed a lot of sand from the beaches with the seaweed. “Now there is a shortage of sand on their beaches,” he said. “We will be more careful.”
Aliotti explained that the sargassum poses potential health risks as long as it is wet. Once the weeds are dry they no longer emit the harmful hydrogen sulfide gases. Because there is so much seaweed landing on the beaches right now, it does not get time to dry before the next batch arrives.
“We know what we have to do to solve the problem,” Aliotti said. “We have to spread it out in thin layers to let it dry.”
That fishermen are happy is not surprising. Sargassum is an important habitat for a variety of marine animals in the open ocean. The sea underneath free floating mats of sargassum is rich in mahi mahi, tuna, dolphins, wahoo and billfish. Sea turtles and marine birds also make sargassum their home.
In 2033, a fishery management plan was put in place for pelagic sargassum in the South Atlantic region. The plan implements restrictions on commercial harvesting, as was done by a North Carolina company who used the seaweed for the feed supplement industry. The plan limits harvest to a maximum of 5,000 pounds wet weight per year. Harvesting is only allowed between November and June to protect turtles. Harvesting within 100 miles of shore is also prohibited.

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