The Microbial Communities In The Sediment Of Apostichopus Japonicus Aquaculture Pond And Influence Of Zostera Marina

In order to investigate the influence of the sediment accumulation on the microbial communities in the sea cucumber(Apostichopus japonicas Selenka)pond,the thesis investigated the vertical variation of environmental factors and microbial communities.We can further evaluate the effect of antibiotic and sanitizer by detecting the proportion of probiotics and pathogenic bacteria.At the same time,we collected the sediment from the pond and coastal area which has the Zostera marina,with the sediment from the pond and coastal area without Zostera marina as controls.By detecting the microbial communities,we can investigate the influence of seagrass on the microbial communities in the sediment.Also it can help us to find out the probiotics which is suitable for the Zostera marina.In the end,we can provide basis data for the plant-microbe environmental repair system.1.The vertical variation of environmental factors and microbial communities in the sediment of sea cucumber pondWe collected the sediment in a sea cucumber pond which is located in Rongcheng,Shandong Province and explored the vertical changes of environmental factors and the microbial communities.The sediment has the characteristics of high-organic-matter,high-nitrogen,high-sulfur and low-phosphate.We can infer that the environment could be deteriorated with longtime accumulated.The H2S and NH4-N accumulated in the anoxia condition could be harmful for the sea cucumber.The dominant bacteria are the phylum Proteobacteria,Acidobacteria,Bacteroidetes,Chloroflexi,Planctomycetes,Gemmatimonadetes and Nitrospirae.The content of Bacteroidetes tends to decrease with the increase of sediment depth,while the contents of Chloroflexi,Gemmatimonadetes and Nitrospirae show the opposite tendency.SPSS correlation analysis shows that the microbial communities are mostly affected by total phosphorus.The abundant sequences of probiotics were detected in our study such as photosynthetic bacteria(PSB),nitrifying bacteria,bacillus and bdellovibrio.There are seldom pathogenic bacterium such as Vibrio and Pseudomonas although they have the tendency of increase in the depth of sediment.Our study infers that the disease outbreaks may caused by the environmental deterioration and the microflora disorders.The use of antibiotic and sanitizer could kill pathogenic bacteria,but also suppress the fuction of probiotics and damage the ballance of microbial communities.2.The influence of Zostera marina on the microbial communities in the sedimentWe collected the sediment from the pond and coastal area where grown the Zostera marina,with sediment from the pond and coastal area without Zostera marina as controls.By detecting the microbial communities,we find the dominant bacteria are the phylum Proteobacteria,Bacteroidetes,Planctomycetes,Acidobacteria and Actinobacteria.There are more Proteobacteria,Gemmatimonadetes,Cyanobacteria,Verrucomicrobia,Deinococcus-Thermus and Chlamydiae in the sediment without Zostera marina.On the other hand,there are more Bacteroidetes,Firmicutes,Deferribacteres,Planctomycetes and Chlorobi in the sediment which has Zostera marina.That may caused by litter and rhizodeposition.The bacteria which only detected in the sediment with Zostera marzina mainly belong to the class Gammaproteobacteria,Actinobacteria and Bacteroidia.Some OTUs belong to photosynthetic bacteria,Saprospiraceae and Rhodopirellula.These bacteria have the function of degrading organic matter and anammox.The study can provide new look at the choice of plant growth promoting rhizobacteria.3 The comparison of microbial communities of different pondWe compared the microbial communities in the ponds located in Rongcheng and Shuangdao bay to discuss the difference of physicochemical property and microbial communities in surface and deep layer.The pond fed by artificial food shows the characteristic of high-nitrogen and high-sulfur and low-phosphate.The phosphate may restrict the distribution of specific microbe.Also there are more Sulfurovum and Desulfobulbus in the surface layer in response to high-sulfur.We analyzed all the 9 samples through PCA and CCA.The results show that the samples from various areas have different distribution on the figure.Also there are significant differences between surface layer and deep layer.CCA analysis indicates the samples in Rongcheng have positive correlation with NO3-N,while the samples in Shuangdao bay have positive correlation with NH4-N,indicating they have different utility pattern of inorganic nitrogen.Our study could exploit the investagation of microbial communities in different breeding environments,could provide useful advices for the regulation of sea cucumber breeding environment.In the end,it has important reference meanings for the utilization of Zostera marina and probiotics in the sea cucumber pond.