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.