Since 2011, massive beachings of Sargassum have been occurring regularly on the Caribbean coast, from Brazil to Mexico and as far away as West Africa. By using a combination of field studies, ecological and physiological experiments and biotechnological processes, the project SAVE-C presents three objectives: (i) acquire basic information on Sargassum species constituting rafts in the nearshore, within bays and in beachings along a latitudinal gradient; (ii) collect and stabilize the biomass; (iii) valorize beachings in two sectors of activities, agriculture (biopesticides/biostimulants) and biomaterials (bioplastics/cartoons) from Sargassum matter. The project groups 15 partners including two partners in Mexico and Barbados. To reply to our questionnings, five workpackages (WP) were designed: WP1 assesses the associated diversity in Sargassum rafts, including environmental parameters in all regions studied. WP2 studies the functioning of rafts and the interactions developed between organisms with Sargassum species including foodweb and nitrogen transfer. WP3 investigates the life-cycle of Sargassum in term of growth, photosynthetic performances, the contamination by arsenic until the degradation process of fragments. WP4 permits to work with local collectivities for the collection of huge biomasses of Sargassum and propose solutions for the stabilization of the biomass before its uses. Finally, this biomass will be used in WP5 as raw material in two industrial sectors: Agriculture and Biomaterials. The consortium will diffuse results to funding Agencies and Caribbean populations, together with transfer to each territorial collectivity knowledge from this project and disseminate to diverse audiences (stakeholders, General Public, students) and participate to new local jobs in West Indies.