This year, 40 million metric tons of sargassum biomass are expected in the Atlantic Ocean, and its collection is projected to increase in Quintana Roo, where it reached approximately 96,000 tons last year, according to Jorge Prado Molina, coordinator of the National Laboratory for Earth Observation (LANOT), based at the Institute of Geography of the National Autonomous University of Mexico (UNAM).
At the conference “Sargassum Detection in the Mexican Caribbean Using Satellite Imagery,” organized by the University Space Program, he stated that large quantities began appearing on the coasts of Quintana Roo in 2022, causing an environmental problem (damage to reefs and seagrass beds) and an economic one, as many tourists have been staying away from the beaches.
The impact is also on health, since this material absorbs arsenic, mercury, and cadmium from the ocean, making it unsuitable for animal feed. Furthermore, if it is deposited in the jungle or any unauthorized location, it contaminates aquifers. And removing it mechanically causes damage because it removes part of the sand.
The scientist mentioned that LANOT has been addressing the issue of its detection for the last six years, with the participation of other organizations. Our first objective was to monitor the patches that arrive in our country and prevent them from reaching the reefs and coasts.
Containment barriers have been installed along 90 kilometers of coastline, but they haven’t been enough given the large amount that reaches the shores. “When it decomposes, it sinks, passes underneath, and ends up causing the brown tide,” he explained.
Sargassum, which originates in the Atlantic Ocean, is actually an ecosystem in itself, he clarified; it is a refuge for fish, crustaceans, and turtles. Its proliferation is due to factors such as global warming and changes in ocean currents; “it can double its volume in 18 days.”
Satellite technology, he pointed out, helps in its monitoring and is just one of the tools for addressing the issue. We use freely available images from the Sentinel-2 satellite, obtained every five days. The study area includes the coast of Quintana Roo and extends into Belize, Guatemala, and part of Honduras, since the sargassum first passes through these countries.
To fill in the gaps between images, ocean current, wind, and wave models have been applied to monitor and predict its arrival. Another model is used to determine where and when the rafts (floating accumulations) of sargassum will reach the coasts of the Mexican Caribbean.
According to Jorge Prado, they rely on the Institute of Marine Sciences and Limnology, which has a unit in Puerto Morelos, to ensure that what is observed in the images is what is happening in the field. A floating GPS is used to obtain location and tracking data, and a spectroradiometer is used to obtain the spectral signatures of the algae.
They have also taken drone images to observe what is happening with this phenomenon and with the reef, the university researcher noted. To display and analyze the information, a web viewer was developed that allows users to determine the distance and quantity of the seaweed ashore; and the dynamic model indicates where it will likely run aground, among other information.
According to the scientist, they have a collection of 4,700 images of the study area, which can be used to conduct retrospective analyses. They also support the dissemination of information on the location of sites and methods for disposing of the seaweed on land, as well as new solutions such as capturing the seaweed offshore to shred it and prevent it from floating.
Source: imagenagropecuaria
