Published on : 08/09/2022 – 00:01
Senegal is the last stage of the Microbiome mission aboard the Tara Ocean Foundation schooner. After nearly two years of navigation, the laboratory boat did not choose the Senegalese coast at random. Along with the waters off Namibia and Chile, it is one of the main upwelling areas in the world, i.e. those areas of vertical currents that cause cold nutrient-rich waters to rise and therefore in fish.
From our correspondent in Dakar,
Despite the rain, the schooner Tara and its scientists set sail to sail off Dakar. On board for three weeks, Samuel Chaffron, researcher at the CNRS, is delighted with the samples collected off the coast of Senegal during this hot season. “ We sampled stations that are in an upwelling zone, therefore an area very rich in nutrients, especially in winter when strong winds drive away the masses of warm water on the surface, explains the researcher. This allows the depths loaded with nutrients to rise to the surface, so the plankton to develop exponentially. In December, an IRD campaign [l’Institut de recherche pour le développement] will return to the same stations, and will also sample. This way, we will have two sampling times to compare, before and during the upwelling. »
In tanks of liquid nitrogen, the scientists carefully store the samples of microbiomes collected from Cape Town – that is to say, those microorganisms in the ocean which are the first links in the food chain, but also essential for capture carbon emissions. ” It also allows the fish to grow a lot. We have areas that are very rich in fish because there is a lot of plankton, and a lot more mammals too, compared to other areas like off the coast of Brazil, which are much poorer in oligotrophic nutrients, continues Samuel Chaffron. We observed much less plankton and no mammals, unlike here. So it’s really two different areas. »
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Romain Troublé, Director of the Tara Ocean Foundation, explains why it is important to study these particular areas of the ocean: “ This particular ecosystem called the microbiome is sensitive to temperature, to climate change, and it is also sensitive to pollution. We are trying with Tara and the researchers involved in Tara’s projects to better understand how it works, what we can predict, if we can also better assess the stocks and the fishing quotas to be authorized so that it is sustainable in the future. . »
Ange Diedhiou, a Senegalese researcher from the Dakar Research and Development Institute, worked for several weeks in the small laboratory installed inside the boat: ” We must first understand the resource, understand its evolution, perhaps possibly integrate them into mathematical models to make predictions in terms of toxicity. Above all, help decision-makers, because we can possibly explain the scarcity of fish, in connection with future plankton or zooplankton, we can perhaps also prevent certain diseases. »
The mission will be on the Casamance River from September 11 to 19 to study microplastics.