Abstract
Microplastic (MP) pollution poses a significant threat to aquatic ecosystems, with increasing evidence suggesting adverse effects on aquatic organisms. This study investigated the impact of chronic microplastic ingestion on gut microbiome diversity and immune responses in Danio rerio (zebrafish) exposed to environmentally relevant concentrations. Zebrafish were exposed to 1 µm polyethylene microplastics at concentrations of 10 µg/L and 100 µg/L for 28 days, alongside a control group. Following exposure, gut tissues were collected for 16S rRNA gene sequencing to assess microbial community structure and diversity, and for quantitative PCR to evaluate the expression of key immune-related genes (e.g., TNF-α, IL-1β, MUC2). Our findings revealed a significant reduction in gut microbiome alpha diversity (Shannon and richness) in the microplastic-exposed groups, accompanied by distinct shifts in beta diversity and altered relative abundances of several bacterial phyla, notably an increase in Proteobacteria and a decrease in Firmicutes. Furthermore, gene expression analysis indicated a dose-dependent upregulation of pro-inflammatory cytokines (TNF-α, IL-1β) and a downregulation of mucin 2 (MUC2) in the MP-treated fish, suggesting compromised gut barrier integrity and an exacerbated immune state. These results underscore the detrimental effects of microplastic exposure on host-microbiome interactions and immune homeostasis in Danio rerio, highlighting a critical environmental health concern with potential implications for broader aquatic ecosystems.
