When chemistry meets taxonomy: Studying glycolipidic chemomarkers in pelagic <i>Sargassum</i> spp. (Phaeophyceae) using molecular networking

To chemically differentiate the three pelagic Sargassum morphotypes co-occurring in floating rafts and drifting across the Atlantic Ocean before stranding on West African, Caribbean, and Atlantic Mexican coastlines, we conducted an investigation of their metabolomic profiles. Hydroethanolic extracts from open-sea raft specimens were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS²), and the resulting spectra were processed through feature-based molecular networking with MetGem software. Several glycolipids were putatively identified through spectral matching and manual annotation, predominantly associated with S. natans var. wingei, S. natans var. natans, and S. fluitans var. fluitans. These findings were corroborated by statistical analyses of ¹H NMR spectral fingerprints. This study represents a chemotaxonomic assessment of pelagic Sargassum utilizing molecular networking, demonstrating its efficient utility for putative chemomarker identification. We further discuss the taxonomic status of the three varieties in light of our chemical data, along with observed physiological distinctions among the morphotypes.