Effects of polymer type and morphology of floating plastic substrates on marine macroinvertebrate recruitment and community succession

Although the community structures of epibenthic macroinvertebrates attached to marine plastic debris may vary according to polymer type, information on this relationship remains limited. This study examined the influence of polymer type and substrate morphology on recruitment patterns and community succession in biofouling macroinvertebrates. From March 2023 to March 2024, recruitment and succession experiments were conducted using four artificial substrates: polypropylene (PP) and polyethylene terephthalate (PET) plates, commercial polyethylene (C-PE) buoys, and commercial PET (C-PET) bottles. Recruitment substrates were deployed monthly and retrieved after 1 month, whereas succession substrates were collected sequentially for macroinvertebrate analyses. Biofouling macroinvertebrate density and biomass were highest on C-PE buoys, likely due to the spherical morphology and shading effect of buoys, which provide favorable physical conditions for larval settlement and persistence. The dominant macroinvertebrate species were the Cnidaria Actinia equina , the Mollusca Magallana gigas , and the Arthropoda Amphibalanus eburneus ; the timing and composition of dominant species were consistent between the recruitment and succession experiments. A. equina and A. eburneus recruitment exhibited species-specific characteristics, while M. gigas exhibited relatively low substrate selectivity. Attached macroinvertebrate communities are formed via recruitment, and their subsequent development is influenced by a combination of substrate characteristics and environmental factors.