Sargassum, North Atlantic calamity

During this period of major departures towards the southern islands before reaching the Antilles, It seems useful to me to relaunch this article which went unnoticed in the heart of summer.

Sargassum (sargassum) are brown algae that grow in the Sargasso Sea, off the coast of Florida and the Bahamas, where they get their name from. Some floating species then drift in a long belt that sometimes extends for thousands of kilometers on the surface of the sea depending on ocean currents and winds.. Many browsers have unfortunately encountered it.

Until 2010 they developed mainly in their region of origin, the Sargasso Sea. In 2011, for a reason probably related to human pollution, but not only, the Sargasso Sea has overflowed. Sargassum has formed a second sea in the ITCZ (Intertropical Convergence Zone) in the north of Brazil.

In these waters with high heat, these brown algae now grow all year round and wash up by millions of tons on the coasts of more than 30 Caribbean countries and from Florida to Brazil. They then decompose quickly, causing an ecological, economic and health disaster. The problem also affects some African coasts. But to date no one knows exactly why Sargassum exploded like this 12 years old.

Research

Gustavo Goni, from February the Atlantic Oceanographic and Meteorological Laboratory of NOAA (¹), Talks about the record volumes of sargassum that scientists detected floating in the sea in the first few months of the year 2023. They peaked around March, thereafter, in a very unusual way, The overabundance of sargassum has begun to decrease. Yet, It remains difficult to predict the extent of the decomposition of sargassum in any given year. Since March 2023 Scientists using satellite data have observed a decrease in the total abundance of sargassum.

Scientists follow the evolution of sargassum in great detail. The monthly bulletins of University of South Florida (²) indicate that there is a significant amount of algae on the beaches this year 2023, compared to most previous years, Although the volume at sea has decreased recently, falling from 15 % between April and May. Further declines are expected in July and August, But researchers say it's hard to know exactly how much will end up on land.

The big questions – what influences the sargassum bloom and why more sargassum washes up on shore from one year to the next – remain key areas of scientific research, and there are no clear answers about it yet.

Land information

Five years ago, Christine Jimenez-Mariani, a French pensioner living in Cancún, Mexico, created Sargassum Monitoring® (³), a website that offers a live map (⁴) of seaweed strandings reported on beaches. Its website is consulted a million times a month, she said, and she also shares photos on Twitter, Facebook, TikTok and other social media sites. She spends her days sorting and uploading photos and videos of sargassum piles on a voluntary basis, from hundreds of contributors.

This website is particularly useful for boaters, informing them daily of the state of beaches and anchorages they might want to frequent.

NOAA publishes regularly updated report on sargassum online (¹). It is collaborating with the University of South Florida to produce this information, And the university also publishes separate data from satellite monitoring. These reveal that the Sargassum Belt was particularly extensive in May in 2018, 2021 and 2022, while it was a little less so in May 2023. Chuanmin Hu, researcher at USF, explains that many factors can influence the growth and flow of sargassum, as well as their arrival on a beach, from brightness levels to ocean currents, through the winds, Temperature and tides.

According to Alfred Lea, University of Texas Medical Branch Researcher, decomposing Sargassum found on beaches can emit ammonia and hydrogen sulfide gases, that can irritate the nose and throat or cause breathing difficulties in people with asthma or other sensitivities. But the breezes that blow over most beaches naturally dilute these gases, which significantly reduces the risk.

Maritime information

For recreational sailors crossing the Atlantic from Europe to the Caribbean and back again, Sargassum banks are above all a hindrance to navigation. Thick slicks of sargassum can even stop boats, clump on propeller shafts, keels and rudders. Many ocean-going racers have had the painful experience of this. And getting into the water to clear these algae can represent a health risk.

The USF (²) publishes daily satellite images reprocessed from the monitoring of sargassum banks. These images are public and free of charge. The developer of SailGrib, Henri Laurent, in turn reprocesses these images to make them very compressed images, that can be downloaded and displayed as an overlay in applications SailGrib WR (Android) or Adrena (Windows), or simply in the app Apple Photos (iOS/macOS). They are then regularly posted online (⁵).

The image is sufficiently compressed, about 100 KB, to be able to download offshore with an Iridium GO!®, or directly in SailGrib WR, either via the SailDocs service by an email request from the application Iridium Mail & Web app :

• • mailto : query@saildocs.com
  • subject [free] in example : Sargassum
  • object : send http://gribserver.sailgrib.com/sat/sargassum_density_most_recent.jpg

A GIF file of the 30 last days is also available, but only with a fast internet connection (±14 MB) (⁵).

This excellent service allows mariners crossing the North Atlantic to know the areas where sargassum is present in order to track its movement and try to avoid it.

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(¹) Atlantic Oceanographic and Meteorological Laboratory
(²) University of South Florida
(³) Sargassum Monitoring®
(⁴) Sargassum Monitoring maps
(⁵) http://gribserver.sailgrib.com/sat/sargassum_density_most_recent.jpg
http://gribserver.sailgrib.com/sat/sargassum_density_most_recent.gif
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Source : Wired relayed by Geogarage blog
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