Exploring Fungal Diversity in Marine Plastic (PET) Wastes and Seafoam in Udo Island, South Korea, with reports of two new species (Leptospora conidiifera and Neodevriesia oceanoplastica)

Marine fungi are key players in ocean ecosystem processes, contributing to organic matter degradation, nutrient cycling, and interactions with other organisms. However, fungal diversity in various environments are still scarce. partly owing to the historical neglect of fungi in ocean research. This study aimed to explore fungal diversity in two underexplored coastal habitats—PET plastic waste and seafoam—collected from the intertidal zone of Udo Island, South Korea. We isolated a total of 88 fungal strains and identified them using multigene phylogenetic analyses and morphological characterization. The strains were assigned to 45 taxa (22 from PET waste and 24 from seafoam). Distinct fungal communities were observed between habitats, underlining the ecological significance of anthropogenic and ephemeral substrates. Two novel species—Leptospora conidiifera sp. nov. and Neodevriesia oceanoplastica sp. nov.—were discovered, along with five species newly recorded in Korea. These findings reveal that PET waste and seafoam serve as reservoirs of unique fungal biodiversity. Marine fungi from such habitats may play previously unrecognized roles in nutrient cycling and microbial interactions in marine ecosystems.