MIAMI.- An “unexpected” excess of nitrogen in sargassum as a result of human activity has made these brown algae a toxic still-life habitat that invades Florida and Caribbean beaches at levels not seen before. now.
This summer, the beaches of Miami Beach have days with great saturation of this foul smelling macroalgae and others with cleaner sands, but with the naked eye you can see a long dark strip of sargassum in the sea that approaches the coast.
A scientific report from the University of South Florida (USF) and the NASA space agency confirmed that sargassum continued to increase in the western Central Atlantic and the Caribbean Sea during last May, which set “a new historical record” for that month.
“2021 will be another important year for sargassum and the amount in the Caribbean Sea is likely to increase continuously during the summer,” that monthly bulletin warned this week.
Sargassum went from being a vital organism for certain marine fauna, a refuge for fish, shrimp and turtles, to a toxic area of still life composed of a large amount of nitrogen, according to a new study by several universities, including the USF and Florida Atlantic University (FAU).
Scientists, including FAU Professor Brian Lapointe, compared a total of 488 samples of the algae collected in the North Atlantic in the periods 1983-1989 and 2010-2019 and found “a 111% increase in the nitrogen-phosphorus ratio. “.
“It was a great surprise,” he told Efe Lapointe, the leader of the investigation, detailing the dramatic changes in the chemistry and composition of sargassum, an algae first described by Christopher Columbus and his sailors in 1492.
Sargassum increases when there are higher levels of nitrogen (EFE)
“It’s a big problem,” explains Lapointe, one of the scientists who identified the Great Sargasso Belt of the Atlantic in 2019, which stretches from Africa to America and spreads with ocean currents.
The study details that a greater availability of nitrogen from natural and anthropogenic sources is contributing to its growth.
“We need to reduce pollution by land-based nutrients, both in Florida and in the main rivers that flow into the Atlantic basin,” Lapointe warns.
Increased nitrogen availability is supporting sargassum blooms and turning an important habitat into harmful algal blooms with “catastrophic impacts on coastal ecosystems, economies and human health,” the research reports.
Special report by our meteorologist Ariel Rodríguez on the invasion of sargassum, an imminent health risk.
“Human activities have greatly altered global carbon, nitrogen and phosphorus cycles, and nitrogen inputs are now considered ‘high risk’ and above a safe planetary limit,” Lapointe laments.
Sargassum that grows along beaches “can result in high concentrations of toxic hydrogen sulfide gas,” which “smells like rotten eggs” and particularly affects people with asthma, health authorities say.
Lapointe recalls that this algae also has “high concentrations of toxic metals, such as cadmium and arsenic”, and also fecal matter, which “represents a high risk for bathers.”
In Miami-Dade County alone, the removal of sargassum has involved costs of more than 45 million dollars annually, while the cleanup throughout the Caribbean in 2018, a record year for sargassum, cost about 120 million dollars, excluding decrease in income from loss of tourism.
SARGAZO, A SEA OF PROBLEMS
The study samples were collected at various sites in the Atlantic, including the southeastern coasts of the US, including Miami and the Florida Keys, as well as Belize, in Central America, and various points in the Sargasso Sea.
Population growth and changes in land use have increased nitrogen pollution and the degradation of estuaries and coastal waters since at least the 1950s, it says.
This pollution supports the growth of the Great Atlantic Sargasso Belt, which receives nitrogen and phosphorus inputs from a variety of sources, including discharges from the Congo, Amazon and Mississippi rivers, Lapointe says.
Outcrops off the coast of Africa, Saharan dust and the burning of biomass from vegetation in South Africa, he stresses, also help its growth.
According to the investigation, this belt has been repeated annually since 2011 and extends up to 8,850 kilometers from the west coast of Africa to the Gulf of Mexico, reaching its peak in July 2018.
“More research is urgently needed,” Lapointe says.
It forced local authorities to implement emerging operations to remove several tons of seaweed from the beaches.
THE THREATS OF PHOSPHORUS AND NITROGEN
In Florida, in addition to sargassum, nitrogen and phosphorus are contributing to the proliferation of other harmful algae in rivers and lagoons that are killing bird fish and especially its iconic manatees.
Starting this week and through September, in the rainy season, several counties and cities in Florida prohibit the use of nitrogen and phosphorous fertilizers.
These components have contributed to the growth of the thick, rotting blue-green algae, known as “guacamole,” as well as the toxic algae called red tide, which has caused fish kills, especially on the west coast of Florida.
Rains from June to September increase the likelihood of carrying fertilizer to ditches and streams that lead to canals, ponds, and rivers, where algae accumulate.
The resulting blooms can kill seagrasses and marine animals that depend on this flora, such as manatees.
This year, these aquatic mammals are starving at a record rate. At least 761 died between January 1 and May 28, according to the Florida Fish and Wildlife Conservation Commission. The record was 830 for all of 2013.