Great Atlantic Sargassum Belt — it is a giant clump of algae that now stretches from the coast of West Africa to the Gulf of Mexico. Its length is approximately 8,800 kilometers, and the mass of algae is estimated at at least 10 million tons. The cluster is so huge that it can be seen from space.
Giant cluster — not a homogeneous mass. The smallest patch of algae seen in satellite imagery is the size of a football field, while the largest reaches 2.5 square kilometers.
“What we're seeing in satellite imagery doesn't bode well for a summer of clean beaches in 2023,” says Brian Lapointe, a research professor at the University of Florida Oceanographic Institute. «We see a bloom like this almost every year, but it's unlike anything we've ever seen before because it keeps getting bigger and bigger. Sargassum is expected to reach the eastern Yucatan Peninsula (both Belize and Mexico) and the beaches of the Greater and Lesser Antilles. The amount of algae on the coasts may increase in the coming months.
The Great Atlantic Sargassum Belt is migrating toward Florida and the Gulf of Mexico, and some of this seaweed will sooner or later come ashore. In 2023, algae appeared unusually early on the beaches of the Caribbean coast of Mexico, as early as February, although the beaches are usually clear of algae until April. And again there are forecasts that this year will set another record for the amount of algae. The environmental organization Red de Monitoreo de Sargazo reports that now only 5 of the 80 beaches on Mexico's Caribbean coast that are monitored daily are completely free of algae. On 10 beaches the amount of algae is excessive, on 20 — large, and on 11 more beaches there are moderate amounts of algae.
The Mexican Navy (Semar), which is responsible for containing algae in the ocean, said that more than 25 thousand tons of algae have already arrived on Mexican beaches, with the most algae on El Recodo beach in Playa del Carmen, near the archaeological zone and in the north of Tulum, as well as on the beaches of Punta Molas, Shakan, Bonitos and Mescalitos on the island of Cozumel. Semar rates the possible level of pollution on many beaches as "excessive", which on the Navy scale is defined as: "Algae accumulations of 70 to 90 cm in height are observed in less than 24 hours, covering almost the entire beach area and making movement on foot and with the use of equipment impossible."
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While scientists are still trying to understand exactly why the organic mass known as the Great Atlantic Sargassum Belt has been growing so rapidly over the past decade, it is clear that the phenomenon is seasonal and originates in the drainages of the region's major rivers, including the Congo, Amazon and Mississippi rivers. As a result of agricultural activities, these runoff are rich in nitrogen and phosphorus, which feed algae. Emissions from burning fossil fuels and biomass, such as trees from deforestation, also contain nutrients that can promote algae growth.
“The blooms are getting bigger, and this year looks set to be the largest on record,” says Dr. Lapointe. In January, scientists recorded the largest algae bloom that month in many years.
According to the Mexican state of Quintana Roo, in 2022, a total of 54 thousand tons of algae were collected on the state's beaches, while in 2021 this figure was 44 thousand tons, and in 2020 — only 19 thousand tons.
Hotels and resorts in Mexico spend millions of dollars each year removing sargassum from their beaches, hiring workers to collect it and transport it to other locations. Not all beaches are equally polluted, and it is always possible to find a clean beach free of algae. It is impossible to predict the appearance of algae on a particular beach.