Abstract

Since 2011, Caribbean and West African countries have experienced the deposit of millions of tonnes of the pelagic brown seaweed sargassum. While these algal blooms are well documented in the Caribbean, less information is available on the occurrence, monitoring and composition of sargassum biomass in West Africa. Cabo Verde (CV), one of the volcanic archipelagos of the Macaronesia region, has experienced sargassum beaching events since 2022, with 2025 being the worst year so far. In this study, high quantities of biomass that were beached in December 2025 (>100 tonnes) were determined in two locations in Santiago—CV’s largest island. Additionally, samples taken in 2024 were analysed to explore the potential valorisation of pelagic sargassum in CV. Elemental composition, amino acid profiling and calculation of NPK ratio suggested that this biomass could be processed for applications towards sustainable agriculture, providing benefits for local development. However, processes would have to include low cost and efficient pre-treatment(s) to manage the content of toxic elements (arsenic, cadmium, and lead). The development of sargassum-derived products for soil amelioration and improvement of crop production could contribute to strengthening communities and empowering local women’s groups, who play key roles in Cabo Verdean agriculture and rural economy.

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