Microplastics Change the Food Utilization of Filter-Feeding Fish via Gut Microbiota

Microplastics (MPs) are ubiquitous in aquatic environments, while their effects on filter-feeding fish are poorly understood. This study aims to explore how MPs change the feeding of planktivorous silver carp. After exposure to MPs, the utilization efficiency of zooplankton by carp increased from 28.45% to 38.63-40.20%, while that of phytoplankton decreased from 50.64% to 40.47-43.32%. MPs did not cause changes in the phytoplankton and zooplankton communities that carp consumed but altered its gut microbiota, leading to increased abundance of genes encoding proteases but decreased carbohydrase genes. Gut metabolomics further showed corresponding metabolic changes especially with increased levels of l-tyrosine, citrulline, succinic acid, and propionic acid, which are significantly correlated with the isotopic signatures of carp utilizing zooplankton. Germ-free zebrafish transplanted with feces of MPs-exposed carp showed metabolic changes like those of carp, verifying that the gut microbiota mediated the effects induced by MPs, while silver carp transplanted with feces of MPs-exposed carp exhibited increased protease activity and enhanced zooplankton utilization efficiency, confirming that MPs could alter its food utilization via gut microbiota. Our findings fill a knowledge gap regarding the ecological risk of MPs to the feeding of planktivorous fish, with potential cascading effects on aquatic ecosystems.