March 4, 2024
Sargasso
Sargassum on the beach. Image: Playa del Carmen Shutterstock The record bloom of algae in
Sargassum on the beach
Sargassum on the beach. Image: Playa del Carmen Shutterstock

The record bloom of algae in the Atlantic Ocean could be explained by the volumes of biomass and fertilizers discharged by the Amazon River.

Sargassum algae, in the right amount, produce oxygen and become habitats for marine wildlife, but excessive bloom compromises the health of corals, beaches, and humans.

The massive deforestation of the Amazon and the dumping of ever-increasing amounts of fertilizers into the oceans could have fueled the largest bloom of Sargassum algae in the Atlantic Ocean: to support this hypothesis, a study published in the journal Science by an international research team which, using data from NASA satellites, has followed the evolution of what is known as the Great Atlantic Sargassum Belt, an immense area of ​​algae that extends from the coasts of West Africa to the Caribbean.

The tide of Sargasso algae in bloom this year stretches some 8,850 kilometers with an estimated weight of more than 20 million tons. This particular type of algae is typical of the central-western Atlantic (the so-called Sargasso Sea) and is well known from the first ocean crossings (even Christopher Columbus reports it in his records).

Algae are not in themselves a problem for the marine environment: within certain quantities, they become a perfect habitat for some animal species such as turtles and crabs, in addition to producing oxygen. However, the excessive blooming recorded in the last 10 years has caused damage to oceanic and terrestrial ecosystems: when large quantities of Sargassum algae reach coastal areas and die, they end up on the seabed, suffocating corals and microalgae. In some cases, clumps of algae can even impede the movement of large marine animals such as dolphins, sharks, and cetaceans.

Sargasso
Sargasso. Image: Playa del Carmen Shutterstock

In addition, when this huge mass of algae reaches the shore, it begins to decompose rapidly, releasing hydrogen sulphide, the gas with the characteristic smell of rotten eggs, which can cause breathing difficulties in asthmatics and has inevitable consequences on the blood flow. tourists in the affected areas.

The team of researchers, coordinated by the USF School of Marine Sciences, has observed an increase in the proliferation of algae since 2011. In an attempt to explain the phenomenon, scholars have tried to relate it to the flow of nutrients introduced into the Atlantic Ocean by the Amazon River, the largest contributor to the birth and development of Sargassum, together with the increase in nutrients from the depths of the West African coasts: according to the researchers, the increase in deforestation and the use of fertilizers in the rainforest in South America, has pumped a record amount of nutrients into the ocean, which in turn has fueled an algae boom.

The hypothesis is still in the preliminary phase, but all the indicators are moving towards a clear link with human activity: “The chemistry of the ocean must be changed to feed such an out-of-control bloom – commented Chuanmin Hu, one of the main Research authors – After nearly 20 years of observations, I can assume that the formation of the Great Atlantic Sargassum Belt will become normal.”

More information: science.sciencemag.org

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