Temporal dynamics of communities on plastic debris in a polluted marine habitat.

This study investigated the succession of prokaryotic and eukaryotic communities on polystyrene panels deployed for 25 weeks in a harbour environment influenced by anthropogenic activities. These activities resulted in an excess of nutrients from sewage and agricultural discharges, as well as the release of hydrocarbons and other pollutants. An eDNA metabarcoding approach targeting the 16S and 18S rRNA genes was used. This innovative methodology allowed a detailed analysis of the community development and succession, providing an in-depth view of biodiversity and ecological dynamics associated with plastic substrates. The microbial biofilm community remained stable throughout the experiment enriched in Rhodobacteraceae (16.97 %) and Flavobacteriaceae (17.99 %). Only minor differences observed between the early and late stages, consistent with their identification as key components of the biofilm. For the eukaryotic community, the early colonization stages were dominated by Alveolata (63.39 %) and Stramenopiles (23.53 %). Later stages showed changes in the community with Chlorophyta (20.14 %) and Opisthokonta (94.32 %) being the most abundant phyla. Richness, as alpha diversity index based on retrieved ASVs, varied from 1875 to 2481 and from 159 to 405 for prokaryotes and eukaryotes, respectively. This indicated an adaptive succession of plastic-associated communities in aquatic ecosystems. Potential plastic-degrading groups found in the prokaryotic community showed a dynamic distribution across colonization stages. Trophic dynamics on plastic debris showed that heterotrophs dominated the eukaryotic community. Our results confirmed the role of plastics as vectors in marine ecosystems, for complex communities composed of bacteria, algae, and invertebrates. This highlighted potential risks to the health of marine ecosystems.