Traveling Seaweeds—Seasonal and Latitudinal Diversity of Epiphytic Seaweeds on Stranded Rafts of the Floating Seaweed Durvillaea incurvata Along the Chilean Coast

Floating seaweeds can be an effective dispersal vector for non-buoyant seaweeds. An under-explored aspect is the examination of seaweed rafts and their non-buoyant seaweed community after the floating journey ends. In this study, we analyzed 476 entire stranded specimens of the floating seaweed Durvillaea incurvata and their associated epiphytes, which were collected during winters and summers of 2023–2025 at four sites along the continental coast of Chile (between 31° S and 41° S). A total of 57 species of epiphytic seaweeds were found, with a higher predominance of Rhodophyta (71.9%). The most representative morpho-functional group was coarsely branched (29.1%). The species Lessonia spicata, Antithamnionella ternifolia, Corallina chilensis, Gelidium rex, G. chilense, and G. lingulatum were found frequently, and 67% of all epiphyte specimens found were reproductive. A higher taxonomic richness of epiphytes was observed at the southern-central sites compared to the northern site, being higher in summer than in winter. These results confirm that epiphytes associated with floating seaweeds are common and that many of these have reproductive structures. Co-occurrence analysis suggests that interactions among morpho-functional groups of epiphytes facilitate long-distance dispersal events. Future studies should assess the physiological viability and ability to reproduce of epiphytes after extensive floating journeys. This would contribute to understanding the effectiveness of rafting dispersal by floating seaweeds on the connectivity of raft-associated algal populations.