Recruitment and succession patterns of macroinvertebrates attached to expanded polystyrene marine plastic debris surfaces

Plastic production has been steadily increasing worldwide; however, research on the ecological impacts of expanded polystyrene (EPS) products commonly used in marine fishing activities remains limited. This study investigated the recruitment and succession patterns of macroinvertebrates colonizing the surface of expanded polystyrene buoys, aiming to understand community changes and provide insights for future marine plastic debris (MPD) management. Fouling macroinvertebrates were sampled monthly from expanded polystyrene surfaces in Jangmok Harbor using a scraper between March 2022 and March 2023. In a recruitment experiment, new expanded polystyrene buoys were deployed monthly; in a succession experiment, 12 expanded polystyrene buoys were deployed simultaneously, and in each experiment, three buoys ware retrieved every month during the study period. A total of 39 species were identified on expanded polystyrene surfaces, with a density of 10,177.4 ind./7.6 m², biomass of 1059.1 g/m², and a diversity of 0.7. The dominant species were Mollusca Mytilus galloprovincialis (40.8 %), Cnidaria Actinia equina (29.1 %). The recruitment experiment showed seasonal variation in species richness, abundance, biomass, and diversity. The succession experiment demonstrated clear differences in community structure each month until a stable community began to form at 5 months after buoy deployment. Notably, two introduced species (Arthropoda Amphibalanus amphitrite and Annelida Hydroides elegans) settled on our expanded polystyrene buoys 1–2 months earlier than observed in previous studies. Together, this result demonstrate that expanded polystyrene buoys can function as habitats and dispersal vectors for opportunistic and introduced macroinvertebrates, potentially driving ecological disturbance in marine ecosystems.