The rapid algal bloom in the Sargasso Sea of the Atlantic Ocean is influenced by human activities - the deforestation of tropical forests and the use of fertilizers. This conclusion was reached by American scientists after analyzing the results of satellite observations of the largest cluster of Sargassum. These algae provide ecosystem integrity and are a habitat for a variety of marine fauna. However, their abnormal reproduction leads to the death of many animal species and the destruction of coral reefs. In recent years, the "red tide" - the bloom on the Atlantic coast - has become a serious environmental problem.
Scientists from the University of South Florida, Florida Atlantic University and Georgia Institute of Technology have hypothesized that the problem of abnormal growth of algae - sargassum - in the Atlantic Ocean is caused by human impact, in particular, deforestation and the use of fertilizers. This is reported by Science magazine.
Experts have been studying the red tide problem for several years. Since 2011, brown macroalgae in the Sargasso Sea began to grow strongly and during flowering occupy vast tropical areas of the Atlantic Ocean - from Africa to the Gulf of Mexico. Last year, authorities in the US state of Florida and British-run Barbados declared a state of emergency over environmental and tourism damage caused by the Sargassum. More than 100 tons of dead ocean dwellers, including dolphins, have been dumped onto the Florida coast by the red tide.
Dolphin Surrounded by Sargassum / University of South Florida.
American researchers studied the results of NASA satellite observations of the Atlantic, which were conducted from 2000 to 2018. Experts have found that the seasonal accumulation of blooming algae colonies - the Great Atlantic Sargasso Belt - is formed by ocean currents.
Scientists also found that the usual flowering regime of sargassum was disrupted in 2011. A significant growth of the algae colony occurred in 2015, with the largest bloom three years later.
Scientists have suggested that the Sargasso belt is formed seasonally in response to the supply of nutrients to the ocean, which occurs for natural and anthropogenic reasons. In recent years, the growth of algae could be strongly influenced by the runoff of the Amazon waters, the researchers said.
NASA satellite observations of the Atlantic / University of South Florida.
Promotional video:
"For the bloom to become so uncontrollable, the chemistry of the ocean had to change," said Hu Chuanmin, professor in the Department of Oceanology at the University of South Florida.
The researchers analyzed rainforest deforestation rates and fertilizer use data in Brazil, and measured nitrogen and phosphorus levels in the waters of the Western Atlantic. As a result, they came to the conclusion about an anthropogenic factor that influenced the rapid flowering of algae.
In common quantities, sargassum algae provide a habitat for turtles, crabs, fish and birds, and also release oxygen through photosynthesis. However, the emergence of an anomalous belt leads to an ecological disaster, experts say. Blooming sargassum thickets make it difficult for marine species to move and breathe. The decayed algae accumulations sink to the bottom and lead to the death of coral reefs. Decaying sargassum releases hydrogen sulfide on the beaches - the smell of rotten eggs repels tourists.
Preliminary results from the study have shown that there is a link between deforestation, fertilizer use, and red tide. However, scientists still need to investigate all the factors and learn how to predict new "outbreaks" of sargassum.
“We hope this incident will serve as the basis for a deeper understanding of the emerging phenomenon, as well as a more effective response to it,” said Hu Chuanmin. "We still have a lot of work to do."
Arseny Skrynnikov