Distinct effects of nano-polystyrene, erythromycin, and their mixtures on the composition and metabolic profile of intestinal microbiota in Nereis succinea

Abstract

Nanoplastics (NPs) and antibiotics are emerging contaminants that co-occur ubiquitously in coastal environments and pose risks to ecosystems. Here, we report the single and combined effects of nano-sized polystyrene (PS) and erythromycin on a marine benthic invertebrate N. succinea at both individual and intestinal microbial levels. It was found that PS at 10 and 1000 μg L⁻¹ and erythromycin at 249 and 7170 ng L⁻¹, individually and in combination, did not cause mortality of N. succinea, but altered organism weight and behaviors and led to morphological changes and oxidative stresses in the intestines. Synergistic effects on glutathione-S-transferase activity and burrowing behavior were observed for mixtures containing high levels of PS. The results of 16S rRNA sequencing showed that erythromycin at both concentrations did not cause changes in microbial composition at the phylum level, while PS and the mixtures significantly increased the relative abundance of Proteobacteria, and reduced Actinobacteriota, Bacteroidota and Firmicutes. At the genus level, erythromycin decreased some potential pathogens such as Vibrio, Nautella, and Pseudomonas, whereas PS and the mixtures reduced beneficial genera such as Megasphaera and Megamonas. Community-level physiological profiles showed that erythromycin and PS had distinct influences on the metabolism of the cultivable intestinal microbiota, with erythromycin enhancing while PS and the mixtures inhibiting the metabolic capacity and diversity. Collectively, our results illustrated that PS NPs and erythromycin exerted distinct influences on the intestinal microbiota of N. succinea, and their mixture effects were dominated by the PS effect.