Scientific studies are trying to understand and explain the resurgence of Sargassum algae

Two recent scientific publications have contributed to knowledge of the phenomenon: The first concerns the important role that the Amazon River plays in the proliferation of algae. As for the second, it attempts to describe the special variation in the concentrations of Arsenic in Algae during their displacement.


The weight of the hand of man on the phenomenon of the proliferation of brown algae is no longer really discussed but it remains to determine the real reason and the way in which it could be alleviated.

These two publications contribute to this challenge.

First of all, Brazilian researchers from the University of Para in BELEM have just made public the first results of their studies on the supposed contribution of the Amazon River to this phenomenon. They have thus established, after 8 oceanographic campaigns, that the nitrogen concentrations recorded on the surface of the water column of the Amazonian continental shelf have never been so high for 10 years.

Scientists believe that anthropogenic factors such as agriculture, deforestation, livestock farming, or even the dysfunction of the treatment of domestic and industrial urban wastewater are unsurprisingly at the origin of the phenomenon.


Sargassum algae



©Cécile Baquey

The important capacity of brown algae to accumulate nutrients and chemical elements is at the heart of the second publication published by researchers from the University of Brest. They set out to compare the concentrations of arsenic between pelagic algae, taken from the Sargassum Sea or in the North Equatorial Current, and those of our coasts. The samples were taken in Guadeloupe and Martinique.

Robert Sargassum pickup

Sargassum seaweed collection operation at sea at Le Robert.



©Capture facebook City of Robert

They conclude that these arsenic concentrations are much higher in the open sea, up to 4 times higher.

These rates decrease when the sargassum touches our land. On the other hand, since nature abhors a vacuum, it is in fact a transference. The algae then take on heavy metals from our discharges: aluminium, iron, chromium, cobalt or manganese.

Sargassum substances


©O. Duflo

The study does not mention it but Chlordecone is also captured by algae.

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