Effects Of EM Probiotic On The Change Of Aquatic Microflora In Pond For Ecological Culture Of Eriocheir Sinensis

In recent years,the production of Eriocheir sinensis breeding has increased rapidly,resulting in a high-density farming situation.A large amount of bait input and nitrogen residues have led to increased pollution of pond water bodies.In order to effectively eliminate the pollution of nitrogen in water,micro-ecological preparations such as EM bacteria are widely used in aquaculture.Nitrogen conversion during the nitrogen cycle is closely related to microbial diversity and community structure.Ammonia oxidation is the first step of the nitrification reaction and a rate-limiting step,which determines the speed of the nitrogen cycle process.In this paper,in view of the advantages of effective environmental protection,such as the ecological water purification of EM micro-ecological preparations,the molecular biology methods such as high-throughput sequencing and real-time fluorescent quantitative PCR are used to explore the early stage of Eriocheir sinensis breeding(April,June,and July)from the perspective of micro-ecological,Changes in the flora of pond water bodies without EM microecological preparation(CK group)and EM microecology preparation(EM group),and the abundance of functional groups of ammonia oxidizing bacteria(AOB)in pond water difference.In order to have a more comprehensive understanding of the mechanism of EM micro-ecological preparation water transfer,promote the development and application of EM micro-ecological preparation in aquaculture.The main results and conclusions of this paper are as follows:1.EM probiotics can increase the diversity and richness of aquatic microflora,and the effect in April and June is better than July.The Shannon index,Ace index,and Chao index of the EM groups were higher than those of the CK groups in April,June,and July.Among them,the Chao index of the EM group in April and the Ace index of the EM groups in June were significantly higher than those of the CK groups(P<0.05),and the other indexes were not significantly different(P>0.05).There was no significant difference in the diversity and richness index of aquatic microflora in July(P>0.05).2.EM can affect the microbial community structure.OTU level hierarchical clustering analysis and NMDS analysis found that the bacterial community structure between the EM groups and the CK groups was significantly different in April and June,but the difference in the bacterial community structure became smaller in July.At the gate level:the relative abundance of Proteobacteria in EM group was significantly higher than that of CK group in April(P<0.05),and in June and July the abundance of each phytophyte was different,but not significantly(P>0.05).At the genus level:the abundance of Brevimonas in the water body of the EM groups was higher than that of the CK groups in April,and the difference was extremely significant(P<0.01).The relative abundance of Arthrobacter in the EM groups was also significantly higher than that of the CK groups(P<0.05).The relative abundance of Aurantimicrobium and Acin etobacter was significantly lower than that in the CK groups(P<0.05).In June,the abundance of Flavobacterium in the CK groups was higher than that in the EM groups and the difference was extremely significant(P<0.01).Although the abundance of the other genus was different,the difference was not significant(P>0.05).In July,the composition of the dominant bacterial group was different between the CK groups and the EM groups,but the relative abundance was not significant(P>0.05).3.The bacterial community structure of the ponds has a time change,and the bacterial community structure is significantly different in different months.The effect of different months on the bacterial community structure is higher than the effect of EM on the structure of aquatic microflora.4.Using EM in Eriocheir sinensis cultivation can increase the richness and diversity of AOB in water bodies.The Shannon index,Ace index,and Chao index of the EM group in April were significantly higher than those of the CK group(P<0.05),and the Shannon index,Ace index,and Chao index of the AOB flora in the water body in June and July were not significantly different(P>0.05).5.At the genus level,the EM probiotics did not significantly change the relative abundance of AOB species,but the Venn diagram based on the OTU level showed that the EM microecological preparation can increase the number of AOB OTUs in the pond water and affect the OTU composition of the AOB in the water body.6.The amount of AOB amoA by fluorescence quantification shows that EM can increase the abundance of AOB.The copy number of the AOB amoA gene in the EM group in April was(7.08±0.51)x105copies/L,which was significantly higher than that of the CK group(6.19±0.07)x105copies/L(P<0.05).In June,the copy number of the AOB amoA gene in the EM group was(5.86±0.39)x105copies/L,and the copy number of the AOB amoA gene in the CK group was(7.06±0.05)x105copies/L,the difference between the two groups was not significant(P>0.05).In July,the copy number of the AOB amoA gene in the EM group was(5.86±0.39)x105copies/L,and the CK group was(4.76±0.61)x105copies/L.The difference between the two groups was not significant(P>0.05).