Seaweed strandings on the beaches of Guadeloupe and Martinique have become a recurring environmental and economic challenge. These strandings involve large quantities of brown algae, known as sargassum, which wash ashore in massive amounts. Researchers and industrialists are trying to repurpose the algae into products like compost or concrete, but progress has been slow. Frédérick Voyer, director of the public interest group Sargasses Martinique, warns that 2026 could be as bad as or worse than 2025. Météo-France has predicted one of the most intense sargassum seasons on record, adding urgency to the situation. In Guadeloupe, officials expect similar levels of algae accumulation as in 2025, when nearly 152,000 cubic meters of sargassum were collected. These strandings have been occurring for over fifteen years, driven by changes in ocean currents that have shifted the algae from their traditional habitat in the Sargasso Sea near the Gulf of Mexico to the Antilles. The warm, nutrient-rich waters of the region have created favorable conditions for the algae's growth. However, as the sargassum decomposes, it releases harmful gases like hydrogen sulfide and ammonia, and it can also contain heavy metals and chlordane, an insecticide. These substances pose risks to both human health and the environment, particularly affecting the tourism-dependent local economy. The Agency for Ecological Transition (Ademe) has pointed out that sargassum can be a valuable natural resource. In Martinique, the company Holdex Environnement has successfully created quality compost from non-contaminated sargassum. However, the company is still waiting for administrative approval to ensure the sargassum is adequately decontaminated from heavy metals. This process is both complex and expensive, requiring the removal of substances like arsenic and chlordane to meet health and environmental standards. Researchers in Guadeloupe have explored using biochar, a material made by heating sargassum in the absence of oxygen, to help decontaminate soil polluted with chlordane. The algae can also be used as a binding agent in the production of concrete, insulators, or bioplastics. However, moving from experimental research to large-scale industrial use remains a challenge. Ademe has received nearly 50 proposals for projects aimed at reusing sargassum since May 2026, but it is crucial to identify which projects are truly viable and which are more opportunistic. Sargassum strandings have become regular since 2018, but this was not always the case. In 2014 and 2015, there were no significant strandings, and in 2020, the amount was minimal. This unpredictability has discouraged investors from building treatment plants, which might remain underused. Sargassum typically arrives between April and October, with very little coming ashore the rest of the year. A recent study by a group of researchers found that among the 28 countries most affected by sargassum, only 17 have developed industries to reuse the algae. Mexico is often cited as a successful example, having announced a $158 million plan to collect sargassum at sea. However, Martinique and Guadeloupe face challenges in creating similar industries due to their smaller size and less developed industrial infrastructure. Satellite data from 2025 show that 38 million tons of sargassum are currently floating in the Atlantic Ocean and the Caribbean Sea, up from 22 million tons in 2022.