Impacts of microplastics exposure on copepod (Eurytemora affinis) and mussel (Mytilus edulis) gut microbiota

Microplastics (MPs) have been found around the world, especially in the ocean. Studies showed that MPs' surfaces can be used by microorganisms as living substrates. Due to the small size, MPs can be ingested by animals and enter the marine trophic chain. MPs can affect animal health by physically causing damage to the digestive tract, leaking plastic chemical components, and carrying environmental pollutants and pathogens into animals. Here, impacts of MPs ingestion on gut microbiota were investigated with studies using two model organisms: copepod (Eurytemora affinis), a model organism in ecotoxicology, and blue mussels (Mytilus edulis), a filter feeder. Organisms were exposed to "virgin" and "weathered" (aged one month in seawater) MPs. Copepods were exposed to low-density polyethylene (LDPE) or polybutylene adipate terephthalate (PBAT) at a concentration of 0.3 mg.L−1 during four generations followed by one "detoxification" generation without MP exposition. Mussels were exposed to LDPE at relatively realistic concentration 0.2 mg.L−1 ("low") and exaggerated concentration 20 mg.L−1 ("high") for 6 weeks, followed by an 8-day post-exposure depuration without MPs. Impacts on microbiota were investigated with 16S rRNA metabarcoding analyses. For copepods, the microbiota of MP-exposed (both PBAT and LDPE) copepods was significantly different from the microbiota of unexposed copepods during generations one to four. Copepod microbiota seemed to return to their original structure after the MP exposure stopped. As for mussels, alteration of gut microbiota and fecal pellets was observed after mussels were exposed to MPs for one week, three weeks and six weeks, and even after 8-day post-exposure depuration. Potential human pathogens were found among operational taxonomic units (OTUs) with increased abundance induced by MP-exposure. Our results have demonstrated impacts of MP-exposure on gut microbiota and suggested possible consequent effects on food safety, the well-being of marine organisms and food web in the ecosystem. Also see: https://micro2024.sciencesconf.org/557968/document