Volksgezondheid, natuur en milieu

Ziet er niet uit en stinkt: Sargassum wier

Toeristen schrikken zich als hun paradijselijke strand bedekt is met een laag rottende bruine blub… Mooi is het zeker niet en het kan behoorlijk stinken als het aan land is gekomen: Sargassum of Sargasso. De Caribische zee heeft al minstens drie jaar last van deze algen. Veel Sint Maartense stranden worden er gedeeltelijk door bedekt en ook in de Curaçaose Annabaai drijft inmiddels het bruine spul. Oorzaak is volgens sommige experts het voedingsrijke rivierwater van de grote rivieren in Zuid Amerika, waaronder de Orinoco rivier. Maar wat is het precies en kan het kwaad? Gelukkig valt dat mee.

zeewier in de Annabaai. Het plastic drijft er helaas al langer...

Zeewier in de Annabaai. Het plastic dreef er helaas al langer…

A strange phenomenon occurred in the Caribbean in 2011. A massive tide of sargassum, brown invasive algae, washed on to the shores of the region’s popular beaches. A similar event is occurring today. Tourism officials are disgruntled by the masses of smelly brown seaweed that are inundating coastlines. Although seaweed is normally seen as a nuisance for local residents and travelers, it does offer some ecological benefits. Plus, sargassum is only temporary and it’s fairly unpredictable, so don’t let its presence in the Caribbean affect your travel plans. Here’s what you need to know about sargassum in the Caribbean.

1. Where Does Sargassum Come From?

The algae originates in the Sargasso Sea in the Atlantic Ocean around Bermuda. The Atlantic is home to two species (S. natans and S. fluitans) which reproduce vegetatively and travel on the ocean’s surface. These two species are also found throughout the Caribbean and the Gulf of Mexico, transported by the Gulf Stream.

2. What Causes Sargassum Invasions?

An explanation for the sudden invasion of tons of algae on Caribbean shores is changing weather patterns and creating warmer temperatures in the region. According to one marine biologist, cooler autumn weather traditionally slows the algae’s growth, plus changes ocean circulation patterns, water temperature and nutrient systems and “typically keep the weed at sea.” As the sea temperature increases, sargasssum is more likely to make its way to the shores of Caribbean beaches.

3. Inhabits All of the World’s Oceans Except…

The Arctic. Sargassum can be found floating on the surface of the Pacific, Atlantic and Indian oceans, but you will not see the brown algae in the world’s most southern body of water.

4. Sargassum’s Healing Powers

The brown algae has been used in traditional Chinese medicine since the eighth century. Sargassum seaweed is a source of iodine used to treat goiters, thyroid disorders, and as a diuretic. It also treats pain from hernias and swollen testes.

5. Sargassum’s Great for Soil

In Tobago, the government has been encouraging farmers to use it as fertilizer. Sargassum is full of nutrients and carbon, making it an excellent natural manure for farmers in the region. Sargassum is also an excellent fertilizer for worn beaches.

6. The Turtles Love It (unless it covers their nests as some of it is doing in Sint Maarten now…)

When sargassum is traveling in the ocean, it acts as both a shelter and food source for turtle hatchlings who are not strong swimmers yet. Green sea turtles will eat large amounts of sargassum throughout their lifetimes. Besides sea turtles, this floating habitat provides food, refuge and breeding grounds for an array of other sea life including crabs, shrimp, mahi mahi, jacks, and amberjacks.

7. Sargassum Protects the Beachfront

The algae serves as buffer on the beach by reducing wave and wind erosion. It also protects the sand in dunes, making them more resilient. Less erosion means more sand on the beaches to structurally support beachfront properties and for people to play in.

8. Food for the Birds

When the sargassum and all of the organisms living within the masses of seaweed wash ashore, it provides food for pelagic seabirds and pelicans.

9. When Sargassum Sinks

Berry-like gas-filled structures, called pneumatocysts, make up the plant. These “berries,” which are filled mostly with oxygen, cause the algae to float. When sargassum loses its buoyancy, it sinks to the seafloor, providing energy in the form of carbon and also food sources to fishes and invertebrates in the deep sea.

10. What’s Next?

Many are wondering if the invasion of sargassum in the Caribbean will be a cyclical occurrence. Marine biologists note that as weather patterns, temperatures and wind speeds change within the Atlantic Ocean and Caribbean Sea, sargassum can be expected. Biologists are working hard to understand the source and patterns of sargassum. You can visit the Sargasso Sea Commission website for updated information.

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