The Dynamic Changes Of Microbial Communities In Aquaculture Environment And Interactions With Water Environment

Pacific white shrimp, Litopeneaus vannamei is one of the world’s famous three shrimp species which has the highest aquaculture production. Litopeneaus vannamei has the characteristics of fast growth and strong disease-resistant ability and gradually become the main farmed shrimp species in south of China.Fishes belongs to Cyprinidae is one of the biggest family and distributed widely, whereas, Cyprinidae fish species are the most abundant in our country.The occurrence of aquatic animal diseases has a close relationship with the aquaculture environment and occurrence of microbial community in the gut of animals.In order to investigate the presence of total microbial communities in the aquaculture environment, parsing the relationship between L.vannamei, Cyprinidae fish diseases and aquaculture environment and presence of microbes in gut. The study investigated the microbial communities structure and diversity in water, sediments, guts of L.vannamei and Cyprinidae fish aquaculture ponds by high-throughput sequencing technology.Results of the study discussed the interaction between environmental factors and microbial communities in water and sediments.1. The dynamic changes of microbial communities in L.vannamei aquaculture environment and interactions with water environment.The metagenomic analysis of water and sediment samples in L.vannamei aquaculture pond showed that the samples which were collected in six different periods,appraised to 31(8) phyla, 66(19) classes, 90(16) orders, 213(96) families, 697(213)genera of bacteria(fungi) including 6(15) genera of bacteria(fungi). The richness and diversity index values of microbes in sediments are higher than water, whereas,abundance and diversity index values of bacteria in each sample was higher than fungi.The collection of water and sediment samples at the same time,composition andabundance of dominant microorganisms has no significant association between two different types of samples.The correlation analysis between environmental factors and microbial communities in water and sediments reported that ammonia nitrogen(AN), chemical oxygen demand(COD), total nitrogen(TN) showed highest impact on bacterial populations in water.The abundance of pathogenic Pseudomonas was positive correlation with TN,total phosphorus(TP),negative correlation with p H,whereas,pathogenic Aeromonas was positive correlation with p H,negative correlation with TN,Nitrite. Pathogenic Flavobacterium and beneficial Bdellovibrio were showed positive correlation with TP,COD,p H,negative correlation with AN.Beneficial Bacillus was positive correlation with TP,COD,AN,and negative correlaiton with Nitrite.In case of sediment samples,water temperature(WT), TN and COD have been recorded significant impact on bacterial population. Pathogenic Pseudomonas were closely positive correlated with TN and COD, whereas, negative correlation was observed with WT. Pathogenic Aeromonas and Escherichia were positively correlated with WT and negative correlated with TN and COD. Additionally, beneficial Bacillus, Streptococcus, Enterococcus and Bacteroides were showed similar results. Pathogenic Flavobacterium was positively correlated with TN and COD, and negatively correlated with WT. The plenty of beneficial Saccharomyces, Aspergillus and pathogenic Fusarium were noted significant positive correlation with TN and Nitrite, whereas it was significantly negative correlated with WT.2. The dynamic changes of microbial communities in conventional fish aquaculture environment and interactions with water environment.According to the results of water and sediment samples from conventional fish aquaculture pond, 26 phyla, 57 classes, 73 orders, 148 families and 380 genera of bacteria were analyzed in water samples which were collected at five different time intervals. Additionally, 33 phyla, 68 classes, 90 orders, 203 families and 648 genera of bacteria were recorded from sediment samples which were collect ed at three different periods. Further, 18 bacterial genera were detected in water and sediment samples which were received at same time from three different places. Diversity index value ofsediment samples was always higher than water samples. Water samples and sediment samples which were collected at the same time, composition and abundance of dominant bacterial populations have not confirmed any obvious correspondence between two types of samples. Correlation analysis of bacterial communities in water and environmental factors showed that main water quality factors which interacts bacterial populations were COD, p H, WT. The richness of pathogenic Pseudomonas in water was positively correlated with TN,TP, and negative correlation with p H value,whereas, the pathogenic Aeromonas was positively correlated with p H, and negative correlation with TN,Nitrite.Beneficial Bacillus and pathogenic Flavobacterium were positively correlated with p H value,COD and negative correlation with Nitrite.3. The influence of aquaculture water microorganisms to microbial communities structure in Cyprinus carpio and Hypophthalmichthys molitrix guts.Metagenomic analysis of aquaculture water and intestinal microflora of Cyprinus carpio and Hypophthalmichthys molitrix recorded 25 phyla,48 classes,72 orders,153 families and 376 genera of bacteria in water samples which were collected in two different time intervals. Whereas, all Cyprinus carpio gut samples identified 24 phyla,47 classes, 68 orders,157 families and 415 genera which were on 28,201411,2014,Hypophthalmichthys molitrix-7 gut sample identified 15 phyla, 29 classes, 40 orders,80 families and 133 genera which was collected on July 11, 2014. In tested water samples, Proteobacteria, Cyanobacteria/Chloroplast, Actinobacteria, Bacteroidetes and Verrucomicrobia were major dominant Phyla(>10%) and in fish guts,Proteobacteria, Cyanobacteria/Chloroplast, Firmicutes, Verrucomicrobia and Planctomycetes were important dominant Phyla. There was a minor difference noted in water samples and intestinal dominant bacteria communities. In Cyprinus carpio-7,Spartobacteria genera incertae sedis has the highest abundance, followed by Unclassified, Gp IIa, and Pasteuria, whereas, in case of Hypophthalmichthys molitrix-7,Unclassified has the highest richness, followed by Spartobacteria genera incertae sedis.64 genera of bacteria was identified in the water,Cyprinus carpio and Hypophthalmichthys molitrix gut samples which was collected on July 11, 2014 and it represents 18.36 % richness of total bacterial communities in collectedsamples.Further, 71 genera of bacteria was noticed in water and Cyprinus carpio gut samples which was taken on April 28,2014 and July 11, 2014,represent 12.31 %richness of total bacterial communities. Maximum abundance was recorded in Cyprinus carpio gut samples which were collected on April 28, 2014. In water and gut samples,potential pathogenic bacteria were identified,namely, Aeromonas, Pseudomonas,Flavobacterium, Klebsiella and Vibrio. The outcome of the present investigation provide a authentic clue that through regulating environmental factors, it is feasible to improve the microbial community structure, inhibit pathogenic microorganisms in the aquaculture environment and reduce the occurrence of diseases in L.vannamei and conventional fishes.