PFAS in pelagic Sargassum: A growing concern for the mexican caribbean coastline

Global pelagic Sargassum blooms have intensified since 2011, affecting over 30 countries worldwide and raising significant environmental and economic concerns. This study presents the first investigation of PFAS in Sargassum, analyzing 40 PFAS in samples from the Mexican Caribbean coastline. Ten PFAS were detected, with a total concentration of 3.88 ± 0.19 ng g⁻¹ (dry weight), dominated by perfluorocarboxylic acids (80.7 %) over perfluorosulfonic acids (19.3 %). Long-chain PFAS comprised 57.1 % of the total measured PFAS, with short-chain PFAS making up the remainder. PFAS mass distribution varied among morphological parts, with blades contributing the most, followed by stems and bladders. Despite accounting for only 10 % of the total dry mass, bladders contributed notably to long-chain PFAS mass due to their lipid-rich and porous structure. Bioaccumulation factors (Log BAF) significantly (p < 0.05) increased with PFAS carbon chain length. This can be attributed to the increasing octanol-water partition coefficient and decreasing water solubility as the carbon chain length of PFAS increases. Estimated annual PFAS loading was 0.51-3.02 kg along the Mexican Caribbean and 34.46-47.21 kg in the Atlantic Sargassum Belt. These findings highlight Sargassum's role as a PFAS vector, complicating its use and disposal while presenting opportunities for pollution mitigation.