Toxicity and Microecological Responses of Daphnia magna and Danio rerio to PVC and PHA Microplastics: Focusing on Trophic Pathogen Enrichment

Microplastic pollution severely threatens aquatic ecosystems, yet the trophic microecological risks of petroleum-based polyvinyl chloride (PVC) and biodegradable polyhydroxyalkanoate (PHA) microplastics remain insufficiently compared. This study established a two-trophic food chain model with Daphnia magna and zebrafish to explore the toxic effects and microbial disturbances of environmentally relevant 0.1 mg/L PVC and PHA. A 21-day chronic exposure induced no physiological damage to the survival, growth, reproduction, and locomotion of both organisms, suggesting conventional phenotypic indicators fail to identify early microplastic stress. However, trophic microplastic exposure triggered prominent zebrafish gut dysbiosis with distinct pathogen enrichment patterns. PHA trophic exposure enriched plant pathogenic genera (Acidovorax, Clavibacter, Rhizobium), whereas PVC trophic exposure accumulated zoonotic and clinical pathogens (Acinetobacter, Neisseria, Mycobacterium, Aeromonas). This work verifies that PHA is not entirely eco-safe, and PVC poses greater ecotoxicological risks via trophic pathogen transmission, providing genus-level evidence for differentiated microplastics risk assessment.