Characterization Of Microbial Community Structures In Aquiculture Pond Sediment And Their Response To Calcium Nitrate For Sediment Remediation

With the development of high density and intensive culture system,sediment pollution in culture pond has become increasingly concerned.Full understanding of the vertical distribution of ions,the structure and diversity of microbial community in the sediment can provide better evaluation and control of the pollution.In order to establish the relationship between microbial community structure in the intensive,high density culture system and physic-chemical parameters of sediment interstitial water,PCR-DGGE technique was used to determine microbial community structure in the sediment of different depth.ELISA was used to measure physic-chemical parameters in sediment interstitial water collected using Dialysis Peeper.Results showed that five bacteria including Bacteroidetes,Proteobacteria,Firmicutes,Verrucomicrobia,Planctomycetes were found.Hierarchial clustering（CLUSTER）and non-metric multidimensional scaling（MDS）analysis showed that the microbial community in sediment core could be divided into three distinct groups,including the upper layer sediment（0-6 cm）,middle layer sediment（7-38 cm）and the lower layer sediment（39-50 cm）.Marglef’s species richness index and Shannon-Wiener diversity index analysis of the vertical microbial communities indicated that middle layer of sediments had higher microbial diversity,which is similar with the results from nature systems.The survey of vertical physicochemical parameters in the interstitial water revealed that NH₄⁺-N concentrations were ranged from 10.98 mg/L to 77.87 mg/L,increasing with the sediment depth and stabilized after the depth of 15-18 cm;PO43--P concentrations were ranged from 0.01 mg/L to0.14 mg/L,declining with the sediment depth and stabilized after the depth of 9-10cm;the concentrations of NO3-N,NO2-N,SO42-,Fe2+ were relatively stable vertically with little variation.BIOENV/BEST analysis found that NH₄⁺-N was the environment factor that has the greatest impact on the microbial communities,followed by PO43--P.These two factors were the main environmental parameters that affected the quality of aquaculture water.After adding Ca（NO₃）₂,total DNA was extracted from the sediment.PCR-DGGE was used to analyze the microbial community structure,and relationship betweensediment interstitial water before and after addition of Ca（NO₃）₂.Results showed that six bacteria Chlorobi,Nitrospirae,Bacteroidetes,Proteobacteria,Firmicutes,Chloroflexi were present.There were three groups in community structure by Cluster analysis.D14,D21,D28 were found in surface sediment in experiment group;D7 was found in surface sediment in experiment group,all bottom sediments,D14,D21,D28 were detected in bottom sediment;D0 was found in surface and bottom sediment in experiment and control groups.Each group varied by its special bands.The Margalef’s and Shannon-Wiener index were in the order a > b > c.BEST/BIOENV analysis showed that NO3-had the greatest influence on microbial community structure（0.787）.Ca（NO₃）₂ stimulated the growth of Bacillus,which had nitration and denitrification ability.Nitrite-oxidizing bacteria proliferated quickly during nitration which might enhance nitration and denitrification ability,resulting in reduced concentration of NO3-,NO2-and NH₄⁺.