[Effects of Microplastic Exposure on Crucian Growth, Liver Damage, and Gut Microbiome Composition]

Microplastics (MPs), which are widely present in the natural environment, may be harmful to the growth and health of aquatic organisms, though studies in this area are lacking. In this study, the crucian carp (Carassius carassius), a type of omnivorous freshwater fish, was chosen as the target, which was fed with fish food containing different concentrations of MPs for a 30-day food exposure experiment to study the effects of MPs on crucian growth, liver damage, and gut microbiome composition. Compared with that in the control group, the body length of the crucians in the environmental groups did not change significantly. The weight of the crucians in the low PE-MPs group increased significantly, but the weight of crucians in the medium and high PE-MPs groups decreased markedly. The liver tissues of the low PE-MPs group of crucians were basically normal, whereas crucians in the medium and high PE-MPs groups had varying degrees of liver damage, and crucians in the high PE-MPs group had the most serious liver damage. At the phylum level, Proteobacteria, Fusobacteria, Firmicutes, and Bacteroides were the dominant species in the gut of the crucians. Pathogens such as Staphylococcus and Ralstonia were present in the crucian gut of environmental groups. Alpha diversity results showed that the gut microbiome of crucians in the high PE-MPs group was the most abundant. PCoA results indicated that the gut microbiome of crucians in the control and environmental groups had obvious clustering characteristics.