It covers the entire ocean – from coast to coast.
During the summer, Sargassum brown algae can grow, covering entire regions in the tropical Atlantic Ocean. In 2018, this “Sargasso Belt” spread to record areas from the coast of Africa to the Gulf of Mexico. According to estimates by Brian Barnes and his colleagues at the University of South Florida, his biomass was at least 20 million tons – algae blooms record in volume. Their article was published in the journal Science.
The authors analyzed satellite observations of algal blooms in the 21st century. It was found that in 2000–2010, Sargasso seaweeds floating near the surface of the island appeared only in summer and autumn, near the Amazon delta, but they did not exist in the Central Atlantic. However, starting in 2011, they began to grow, forming a “great sargasso belt” across the ocean, and since then this has been repeated every summer (except for 2013). In 2018, the sprawl was record-breaking, producing ten times more biomass than in 2011.
The emergence of the “Great Sargasso Belt,” scientists associated with the flow of pollution into the waters of the Atlantic, washed away from agricultural land. Especially large amounts of nitrates and phosphates are carried out by the Amazon, and the continued reduction of forest cover around the river only stimulates this process. The second most important source of pollution, the authors call the countries of West Africa, leading active extraction of water from underground sources for watering plants. This water also ends up in the ocean, and with it the minerals that play the role of “fertilizer” for the Sargasso.
Brown algae floating islands are an important part of local ecosystems. They provide shelter to marine animals, fish and birds. However, the endless spaces covered with such a “blanket” become dangerous. They damage corals, are carried by many tons to the shore and decompose, causing damage to local residents. It remains only to guess what the summer of 2019 will turn out for the “Sargasso Belt”.