Sargassum reaches Miami and the Caribbean much more toxic

A “unexpected” excess Nitrogen in Sargassum resulting from human activity has made these brown algae a toxic still life habitat that is invading beaches in Florida and the Caribbean at levels never seen before.

This summer, Miami Beach beaches They 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 approaching 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 West Central Atlantic and Caribbean Sea in May, which set “a new all-time record” for that month.

“2021 will be another important year for Sargassum and the quantity in the Caribbean Sea is likely to increase continuously during the summer,” this monthly bulletin warned this week.

Sargassum went from being a vital organism for certain marine fauna, a refuge for fish, shrimps and turtles, at a toxic zone still life composed of a large amount of nitrogen, according to a new study conducted by several universities, including USF and Florida Atlantic University (FAU).

Scientists, including Professor Brian Lapointe of the FAU, compared a total of 488 algae samples collected from the North Atlantic during the periods 1983-1989 and 2010-2019 and found “a 111% increase in the ratio nitrogen-phosphorus “.

“It was a big surprise,” said Lapointe, head of the investigation, detailing the dramatic changes in chemistry and composition Sargassum, an algae first described by Christopher Columbus and his sailors in 1492.

“It’s a big problem,” explains Lapointe, one of the scientists who identified in 2019 the Great Sargasso belt of the Atlantic, which stretches from Africa to America and spreads with the currents of the sea.

The study states that a greater availability of nitrogen from natural and anthropogenic sources contributes to its growth.

“Need Reduce the pollution by nutrients of terrestrial origin, both in Florida and in the main rivers that flow into the Atlantic basin, ”Lapointe warns.

The increased availability of nitrogen supports Sargassum blooms and transforms important habitat into harmful algal blooms with “catastrophic impacts on coastal ecosystems, economies and human health,” the research reports.

“Human activities have dramatically altered the global cycles of carbon, nitrogen and phosphorus, and nitrogen inputs are now taken into account. high risk’ and above a safe planetary limit ”, deplores Lapointe.

Rotten egg

Sargassum that grows along beaches “can cause high concentrations of toxic hydrogen sulfide gas”, which “smells like rotten eggs” and particularly affects people with asthma, say the health authorities.

Lapointe recalls that this algae also has “high concentrations of toxic metals, such as cadmium and arsenic ”, as well as fecal matter, which “represents a high risk for swimmers”.

In Miami-Dade County alone, the disposal of Sargassum resulted in costs of more than $ 45 million per yearWhile the cleanup across the Caribbean in 2018, a record year for Sargassum, cost around $ 120 million, not to mention declining revenue from lost tourism.

A sea of ​​problems

Study samples were collected from various sites across the Atlantic, including the southeastern coasts of the United States, including Miami and the Florida Keys, as well as Belize, in Central America, and various points of the Sargasso Sea.

Population growth and changes in land use have increased nitrogen pollution and degradation of estuaries and coastal waters since at least the 1950s, he says.

This pollution supports the growth of the Sargassum belt of the Grand Atlantic, which receives inputs of nitrogen and phosphorus from various sources, including discharges from the Congo, Amazon and Mississippi rivers, Lapointe says.

He points out that the outcrops off the African coast, the Saharan dust and biomass combustion vegetation in South Africa.

According to the survey, this belt has been repeated every year 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,” says Lapointe.

Other toxic algae

In Florida, in addition to sargassum, nitrogen and phosphorus contribute to the growth of other harmful algae in rivers and lagoons they kill bird fish and in particular their iconic manatees.

From this week to September, during the rainy season, several counties and cities in Florida prohibit the use of nitrogen and phosphorus fertilizers.

These components contributed to the growth of the thick, putrid blue-green algae, known like “guacamole”as well as the poisonous algae called red tides, which have killed fish, especially off the west coast of Florida.

Rains from June to September increase the likelihood of carrying fertilizer to ditches and streams that lead to canals, lagoons and rivers, where algae collects.

The resulting blooms can kill seagrass beds and marine animals that depend on this flora, such as manatees.

This year, these aquatic mammals they are starving at a record pace. At least 761 people died between Jan. 1 and May 28, according to the Florida Fish and Wildlife Conservation Commission. The record was 830 for all of 2013.

EFE