Microplastic ingestion by the polychaete community in the coastal waters of Kochi, Southwest coast of India

Abstract

Microplastic pollution in marine habitats and the impact they create on the biota of higher trophic levels have garnered research attention globally. This present investigation attempted to evaluate the distribution of plastic litter of varied sizes; macro, meso, and microplastics in the immediate benthic habitat i.e., in the sediments and in polychaete tubes, and its subsequent ingestion by the dominant macrobenthic invertebrate, Polychaeta in the near-shore coastal waters of Kochi, southwest coast of India during dry and wet periods of the years 2019 and 2021. Polychaetes belonging to five families Onuphidae, Lumbrineridae, Nereidae, Spionidae, and Pilargidae comprising species of genera Diopatra, Lumbriconereis, Dendronereis, Nereis, Ceratonereis, Prionospio, and Ancystroscylli dominated the benthic community during the study period and hence were selected for the microplastic ingestion analysis. Higher microplastic ingestion was observed in the family Onuphidae (67%) followed by Lumbrineridae (22%), Nereidae (8%), and Pilargidae (3%). A significant variation in microplastic ingestion was evident with the season and between the different sampling years with more ingestion by polychaetes of the dry-’21 (46%). Interestingly, no evidence of microplastic ingestion was observed in Prionospio sp the surface deposit feeders. No prominent relation was observed with the respective length and wet weight of the analysed polychaete species. Polyethylene (PE) fragments of white and blue colour dominated the sediment, tubes, and the polychaete community. Furthermore, to have a better perception of possible microplastic fragmentation in the environment and the potential toxicity its elements may generate on the aquatic biota, the morphological characteristics and the elemental composition of the microplastics were evaluated through SEM-EDS analysis. The SEM analysis revealed cracks and roughness on the surface of microplastics indicating microplastic fragmentation while the EDS analysis exhibited the presence of toxic elements thus signifying the potential toxicity that marine debris can evoke on aquatic life.