Gut and fecal microbial community responses of a marine copepod to micro(nano)plastics

Micro(nano)plastic (MNPs) pollution in the ocean raises concerns about their ecological risks. This study investigated the responses of gut and fecal microbiomes of a marine copepod Calanus sinicus to MNPs exposure. Using aggregation-induced emission luminogen bacterial probes, we first visualized and quantified the bacterial distribution and abundance changes in copepod gut and fecal pellets following 200 μg/L of MPs (5 μm) and NPs (50 nm) exposure. Results revealed bacterial colonization in the anterior midgut, but MNPs induced significant increase in gut bacteria with a shift in gut/fecal balance. Specifically, the average fluorescence intensity of gut bacterial clusters increased by 51.8 % and 74.4 %, and conversely fecal bacterial abundance reduced by 41.4 % and 52.0 %, upon MPs and NPs exposure, respectively. Metagenomic sequencing revealed that MNPs exposure resulted in reduced community diversity of fecal microbiome, characterized by decreased core groups and enriched plastic-associated genera. The most abundant Pseudophaeobacter decreased by 18.7–20.5 % under MNPs exposure. Short-term MNP exposure had no major impact on KEGG pathways and CAZy classes, but significantly upregulated the MNP degradation-related functions, also disrupted the key genes involved in metabolism, oxidative stress, and biofilm formation. These findings provide key insights for the disturbance posed by MNPs to copepod guts and fecal microbiota. • MNPs exposure increased copepod gut bacterial abundance but reduced their fecal abundance. • MNPs exposure reduced copepod fecal microbiome diversity and caused loss of core taxa abundance. • Plastic-associated genera and genes were enriched under MNP exposure. • Copepod fecal microbiomes shows adaptation and functional redundancy in response to MNPs.