Effects of BDE-209 exposure on growth performance, intestinal digestive enzymes, and intestinal microbiome in common carp (Cyprinus carpio L.)

Polybrominated diphenyl ether has become a widespread environmental pollutant in aquatic environments. BDE-209, a prominent PBDEs found in the environment and wildlife, has been proven to cause oxidative stress, immune damage and endocrine system disorders in fish. However, the effects of BDE-209 on the intestinal health of fish remain unclear. This research aimed to determine the effects of BDE-209 on the growth performance, digestive enzymes activities and intestinal microbiota of common carp. After 60-day exposure, the growth performance of common carp were remarkably decreased (P < 0.05). Moreover, the levels of protease, amylase and lipase activities remarkably decreased by BDE-209 exposure (P < 0.05). In addition, metagenomics analysis revealed that the alpha-diversity values of intestinal microbiota were significantly decreased in BDE-209 exposure groups (P < 0.05). The results also indicated that BDE-209 exposure could alter the intestinal microbial compositions. At the phylum level, the proportion of Fusobacteria was markedly reduced (P < 0.05), while the proportions of Bacteroidetes and Firmicutes were significantly increased (P < 0.05) along with the increasing concentrations of BDE-209. At the genus level, the proportion of Shewanella was higher (P < 0.05) in BDE-209 exposure groups than in control group, while the abundance of Cetobacterium showed an opposite trend. Furthermore, the proportions of some aquatic probiotics (such as Bacillus, Rhodopseudomonas and Lactobacillus) were significantly enriched (P < 0.05) in control group, and the content of short-chain fatty acid producing bacterium (such as Faecalibacterium, Bacteroides and Clostridium) were decreased along with the increasing BDE-209 concentrations, but no significant differences were found among the four groups (P > 0.05). Overall, exposure to BDE-209 could alter the intestinal microbiota of common carp, which may affect their growth and threaten their health.