Study On Water Quality And Microbial Community In Litopenaeus Vannamei Intestine And Aquaculture Environment

Litopenaeus vannamei is one of the main prawn breeding species in China,which has the advantages of strong resistance to stress or disease,rapid growth and long reproduction cycle.The culture environment is closely related to the growth of prawn.From May to July 2018,water,sediment and L.vannamei intestine samples from the aquaculture ponds were collected in Shanghai Fengxian Prawn Cooperative.The microbial community of water,sediment and L.vannamei intestine samples at the age of 46d and 86d were analyzed.The research results explained the correlation of microbial community structure between the L.vannamei intestine and the environment,as well as the differences that appeared with prawn age.From June to September 2019,water quality monitoring on the overall process of aquaculture was conducted in Shanghai Yuye Prawn Cooperative,and the water sample was collected every 7 days.There were 11 indicators to be inspected,which were T,p H,DO,TN,NO₂^--N,NO₃^--N,TAN,TP,AP,and chlorophyll a.In the 73d,93d,and 109d of culturing,the microbial of sediment and the L.vannamei intestine were collected and analyzed.Then the differences of the microbial in sediment and the L.vannamei intestine that in healthy or diseased pond were researched.The main results were as follow:1. During the culturing process of L.vannamei in 2019,the tested indicators of water quality basically met the requirement of the growth of L.vannamei.There were significant differences?P<0.05?on p H,TP,TN,NO₂^--N and NO₃^--N within 4 ponds.There were multiple indicators in Pond 3 that had significant differences with other 3ponds.The p H in Pond 3 was significantly lower than Pond 1,2 and 4,and TN,NO₂^--N and NO₃^--N were significantly higher than the other ponds.2. Illumina Mi Seq high-throughput sequencing platform was used to analyze the microbial community in the gut of L.vannamei at age 46 and 86,respectively.The Alpha diversity indexes in water samples were significantly lower than that in sediments and shrimp intestines.We detected 35phyla,71 classes,155 orders,274families and 277 genera that existed in water,sediments and L.vannamei intestines.There were more common microbial in the intestine of L.vannamei and the sediments than those in intestine and water.The microbial community structure of water,sediments and L.vannamei intestines changed when culturing time prolonged,the different phyla of 46d and 86d were Actinobacteria,Chlorobi,Fibrobacteres,Planctomycates and TM6?P<0.05?.Relative abundance increases with time.However,the dominant flora was relatively fixed.At the phylum level,Proteobacteria,Bacteroidetes,Actinobacteria were the three most dominant categories in all three samples.At the class level,Alphaproteobacteria,Betaproteobacteria and Actinobacteria were the most dominant categories.In addition,L.vannamei intestines and sediment had the common advantage class of Deltaproteobacteria,Gammaproteobacteria and Gemmatimonadetes.From the classification level of order,family and genus,the microbial community relative abundance in various samples presented differences,so that few common categories showed advantage in each samples except unclassified genera,which was the most abundant in all the samples.Besides,hgc I?clade was the dominant genus in the water,ambiguous?taxa was the predominant genus in the L.vannamei and sediment.These results furtherly explained the correlation of the microbial community structure in intestine of L.vannamei and its aquaculture environment,and also showed the differences happened during the culture process.3. High-throughput sequencing was conducted on the samples from the sediment and L.vannamei intestine at 73,93 and 109 d,following with alpha diversity index analysis and community analysis.The alpha diversity index analysis indicated that the Chao1,Observed Species,Shannon-Wiener and Simpson indexes in the sediment were significantly higher than the L.vannamei intestine?P<0.05?,which further showed that the sediment has a larger microbial community diversity.In the sediment and intestine,the three dominant phyla were Proteobacteria,Bacteroidetes and Firmicutes;the dominant classes in the sediment were the Proteobacteria,Bacteroidetes and Deltaproteobacteria;the dominant classes in the intestine were Bacteroidetes and Clostridium.The dominant genera in the sediment were MND1,Thiobacillus,Helicobacter and Bacteroides.The dominant genera in the intestine were Helicobacter,Bacteroides,Mucispirillum,Bifidobacterium,Lactobacillus,Lachnospiraceae?NK4A136?group,Lactococcus and Aeromonas.The differentiating microbe communities?P<0.05?in the samples from sediment and intestine in both healthy and diseased ponds were researched as follow:In the level of phylum,the content of Chloroflexi,Deferribacteres,Gemmatimonadetes,Latescibacteria,Nitrospirae,Zixibacteria in the sediment and the Bacteroidetes in the intestine in the diseased pond were significantly higher than the healthy pond.The content of Bacteroidetes,Fusobacteria,Spirochaetes in the sediment,and the Proteobacteria,Tenericutes,Deferribacteres in the intestine from the diseased pond were significantly lower than those of the healthy pond.The Deferribacteres,Fusobacteria and Bacteroidetes showed significant differences in both sediment and intestine.In the level of class,the Gammaproteobacteria and Bacteroidia both showed significant differences in both sediment and intestine from healthy and diseased ponds.In the level of genus,Aeromonas and Helicobacter both showed significant differences in both sediment and intestine from healthy and diseased ponds.The possible causes of the disease of L.vannamei may be the increased contents of pathogenic bacteria like Bacteroides and Helicobacter in the microbial of the sediment and intestine,as well as the insufficient probiotics like Bifidobacterium and Flavobacterium in the environment.It is advised to add probiotics properly during the aquaculture process.