Multiple effects of ZnO nanoparticles on goldfish (Carassius auratus): Skin mucus, gut microbiota and stable isotope composition

The skin and the gut are direct target tissues for nanoparticles, yet attention to effects of metal-based nano-particles (MNPs) on these two and the discrepancy in these effects remain inadequate. Here, effects of ZnO nanoparticles (nZnO) on skin mucus and gut microbiota of goldfish (Carassius auratus) were investigated, as well as further elements turnover and metabolic variations. After 14 days of exposure, considerable variations in levels of biomarkers (protein, glucose, lysozyme and immunoglobulin M) in skin mucus demonstrated significant stress responses to nZnO. nZnO exposure significantly reduced the abundance of Cetobacterium in the gut while increased that of multiple pathogens, and further leading to down-regulation of pathways such as carbohydrate metabolism, translation, and replication and repair. Decreased delta 15N values indicated declined N turnover in vivo, further demonstrating the negative effect of nZnO on metabolism in the organism. Integration analysis of each biomarker using the biomarker response index version 2 (IBRv2) revealed concentration-dependent effects of nZnO on skin mucus, while effects on physiology in vivo was not, demonstrating the discrepancy in the toxicity pathways and toxic effects of nZnO on different tissues. This work improved our understanding about the comprehensive toxicity of nZnO on aquatic organism.

Automated summary

This study investigated the effects of ZnO nanoparticles (nZnO) on the skin mucus and gut microbiota of goldfish, as well as the elements turnover and metabolic variations. The results showed that nZnO exposure significantly impacted the levels of biomarkers in the skin mucus, and reduced the abundance of beneficial bacteria in the gut while increasing the presence of pathogens. Integration analysis revealed concentration-dependent effects of nZnO on the skin mucus, highlighting the discrepancy in toxicity pathways and effects on different tissues. This work enhances our understanding of the comprehensive toxicity of nZnO on aquatic organisms.