Sandy Haze from the Sahara Promotes Sargassum Seaweed Growth


No, this is not a tongue-twister. C. Everard (France-Antilles) reports that “what is really going on” in the Caribbean is happening several thousand kilometers away: iron and phosphate dust from the Sahara sands promotes the growth of seaweed in the Atlantic Ocean [and Caribbean Sea].

Observe the air; it was so difficult to breathe for several months. Then this ocean, covered with Sargassum seaweed. The two phenomena are linked, which was revealed by U.S. scientists in Missouri. Their study is not new (we had already mentioned it) but it is the right time to bring it out again because both phenomena are currently affecting us. Scientists studied the invasion of seaweed in 2011 on all Caribbean coasts. [. . .]

At the time, everyone thought that the sargassum came from the Sargasso Sea, located in the North Atlantic. The assumption, however, was never verified. Despite their attempts, American scientists “have not succeeded in linking the Caribbean invasion to the North Atlantic and the Sargasso Sea.”  However, they used a numerical model for current flows. Thus, they discovered that the seaweed actually grew in the South Atlantic, at the level of the “North Equatorial Recirculation Region” (NERR).

This is a swirling ocean current where growing conditions are ideal for seaweed. The waters are warm there, and nutrients are plentiful. This is where our sandy mist comes in!

Indeed, if a significant quantity of nutrients comes from the River Congo (in Central Africa), the Amazon, and the upwelling of cold waters from the deep, the [in]famous sandy dust also plays a role. These are especially rich in iron and phosphates and when their path meets the Sargassum seaweed, they feed it. On the 2011 episode, Franck Mazeas—of the Environment, Planning and Housing Office of Guadeloupe—commented: “The unusual nature of this event could be associated with greater fluctuations of the dynamics of regional ecosystems, particularly in connection with climate change.” It seems that the years that followed vindicated the scientists [and their work, published as “The Sargassum Invasion of the Eastern Caribbean and Dynamics of the Equatorial North Atlantic” by Donald R. Johnson, Dong S. Ko, James S. Franks, Paula Moreno, and Guillermo Sanchez-Rubio (Center for Fisheries Research and Development, Gulf Coast Research Laboratory, University of Southern Mississippi, Mississippi; Ocean Dynamics and Prediction Branch, Naval Research Laboratory, Stennis Space Center, Mississippi).

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