Seaweed Odor Effect

A sparkling blue ocean, warm sand and palm trees — and then there’s the stinky seaweed blob. It’s been an ugly reality along Florida beaches and in the Caribbean this spring and summer, with a record amount of the floating brown algae known as sargassum washing ashore. The tentacled mass can harm wildlife, irritate beachgoers and even cause respiratory problems for those with asthma.

When the seaweed hits land it emits hydrogen sulfide, a gas that smells like rotten eggs. It’s also dangerous to swim near it, as tiny sea creatures that live inside the sargassum can sting people who get too close. And it can smother sea turtle nests and clog sand dunes.

But while the sargassum is an eyesore, it’s also a crucial habitat for marine life and is used for biomass that produces food, fuel and pharmaceuticals. And although it can be hazardous to humans if touched, the foul-smelling algae isn’t a threat to health when in small amounts, according to Florida Health.

The rotting seaweed releases the noxious gas because of bacteria living inside it that produce dimethylsulfoniopropiante, or DMS, in their cells. When the DMS is broken down, it emits hydrogen sulfide. The gas can irritate the skin and lungs and is dangerous for those with respiratory illnesses, such as asthma, or who are pregnant, according to Florida Health.

Scientists have been studying the bacteria and kelp that produce the gas to find out how they work together. They found that the sulfoniopropiante is converted to volatile compounds called aldehydes by the bacteria. The compounds then combine with sulfur to form hydrogen sulfide.

These chemicals are what gives seaweed the rotten egg odor, and the more they produce, the stronger the stench. But if the bacteria are not producing the volatile aldehydes, the smell isn’t as bad. The scientists also looked at kelp from a local fish farm, and they found that the sulfoniopropiante levels there were much lower than in the sargassum.

Scientists are not sure why the sulfoniopropiante and DMS levels are so high in the sargassum, but they believe it’s related to ocean currents. They may also be affected by climate change. And there’s some good news: Researchers have noticed that the amount of the volatile compounds has decreased in February, which is the first time this has happened since they started tracking the sargassum with satellites in 2011. That could mean less odor and more pleasant beach days ahead. Scientists hope that if the trend continues, it will also mean more good seaweed. Because the sargassum is rich in umami, or savory taste, it’s a tasty addition to sushi and other Japanese dishes. The sargassum has also provided chefs with the opportunity to develop new seafood dishes. But this umami isn’t just in flavor, it’s also in the texture. It can give a creamy quality to clams and oysters, and also make mussels plump and meaty. And the sargassum is an important ingredient in some of South Florida’s best restaurants.