The Sarg’Alien project focuses on the proliferation of Sargassum muticum, an invasive macroalgae native to Japan, which has been present in the Bay of Seine since the 1970s. In recent years, its expansion has intensified along the Côte de Nacre, causing ecological disruptions and impacting human activities such as fishing, tourism, and beach management. Massive algal strandings during the summer also generate environmental issues, notably the emission of toxic gases like hydrogen sulfide. This proliferation could also alter current indicators of coastal water quality. Green algae of the genus Ulva are currently used to assess eutrophication under the Water Framework Directive, but their competition with Sargassum could challenge this role. The project therefore aims to better understand the invasion dynamics of Sargassum muticum and evaluate its potential as an environmental indicator. Sarg’Alien features a multidisciplinary approach combining marine ecology, biology, and remote sensing, and is structured around three main objectives:
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Analyze the proliferation dynamics of Sargassum through seasonal field monitoring in intertidal and subtidal zones. These observations will allow for biomass estimation, identification of environmental factors favoring their development, and the study of beaching phenomena;
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Develop remote sensing tools to map and estimate Sargassum biomass, both in the marine environment and on the foreshore;
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Evaluate the potential of Sargassum muticum as an indicator of coastal water quality.
This project aims to deepen the understanding of this invasive species and design operational tools for the ecological monitoring and management of the Normandy coastline.
