Effects of complex probiotics on water quality and microbial communities in grass carp(Ctenopharyngodon idellus)culture

This experiment was conducted to study the effects of complex probiotics on water quality and microbial community structure in grass carp culture.The results of water quality determination showed that compared with the control group,the concentration of ammonia nitrogen,nitrite nitrogen and total nitrogen in treatment group was lower in the whole experiment,respectively;On 18th d,the concentration of nitrate nitrogen in treatment group was decreased by 54.49%(P0.05).On 15th d,the concentration of total inorganic nitrogen in treatment group was decreased by 28.75%(P0.05).Orthophosphate and total phosphorus had no difference between the two groups.The 454-Pyrosequencing results showed that the composition of bacterial communities was highly variable between control and treatment groups,and microbial diversity of treatment was higher than that of control.Firmicutes and Proteobacteria decreased by 91.21%(P0.01)and 21.75%(P0.01)respectively.Bacteroidetes,Actinobacteria and Cyanobacteria increased by 288%(P0.01),435%(P0.01)and 848%(P0.01)respectively.Among Proteobacteria,Alphaproteobacteria and Betaproteobacteria was elevated by 318%(P0.01)and 18% respectively,while Gammaproteobacteria was reduced by 78.82%(P0.01).