Effect Of Adding Bacillus Spp On The Microbial Community Structure And Physicochemical Factors In Grass Carp Ponds

Now pond culture is the main mode of aquaculture in China,and its output is close to half of the total national aquaculture production.Among them,the freshwater pond aquaculture production accounted for 72%of the total freshwater aquaculture production.Aquaculture pond water is getting worse due to the increase of organic matter such as excrement,biological residue and residual bait entering the pond.At the same time,the random discharge of aquaculture tail water has also caused serious environmental pollution problems.The results show that the structure of microbial community and the physical and chemical factors of pond water are interacted.The metabolic decomposition of microorganisms in water significantly affects the composition and content of nutrients in water.In order to study the effects of Bacillus spp on microbial community structure and physical and chemical factors in pond water,the relationship between microbial community structure and pond water physical and chemical factors in grass carp culture was determined.This paper compared and analyzed the physical and chemical indicators of the surface and bottom water of three experimental groups?addition of Bacillus spp ponds?and three control groups?ordinary ponds?in Zhongshan City People's Town,and uses high-throughput sequencing technology to microbial communities in the surface and bottom water.to the results would provide theoretical support for the analysis and evaluation of the effect of adding Bacillus spp pond microorganisms on the culture environment.the main findings are as follows:1.Effect of Bacillus spp addition on the structure and physical and chemical factors of eukaryotic microorganisms in grass carp pondsIn order to study the effect of Bacillus spp on eukaryotic microbial community structure and physical and chemical factors in grass carp ponds,the high-throughput sequencing technology was used to analyze the eukaryotic microbial community structure in the experimental group?Bacillus spp added pond?and the control group?ordinary pond?in August and September 2017,respectively.At the same time,the physical and chemical indicators of the two ponds were analyzed.The results showed that The contents of TN,NH₄⁺-N and NO₃^--N in the pond water of the experimental group in August and September 2017 were significantly lower than those in the control group?P<0.05?.The results showed that the abundance of Cyclotella meneghiniana,Trichosporon,Chroomonas,Hedriocystis and Cyclotella in the pond water of the experimental group was significantly higher than that in the control pond?P<0.05?.The Chao1 index and Shannon index of the eukaryotic microbes in the experimental group were significantly higher than those in the control group?P<0.05?.The experimental results confirmed that by adding Bacillus spp to the pond,the structure of the eukaryotic microbial community in the water could be changed,thereby realizing the adjustment of the physical and chemical factors of the pond.2.Effect of Bacillus spp addition on prokaryotic microbial community structure and physicochemical factors in grass carp pondsIn order to study the effect of adding Bacillus spp in the pond on the physicochemical factors and prokaryotic microbial community structure,the prokaryotic microbial community structure of the experimental group?Bacillus spp added pond?and the control group?ordinary pond?were analyzed by high-throughput sequencing technology in October 2017,January,April,April,July and October,respectively.At the same time,the physical and chemical indicators of the water in the two groups of ponds were analyzed.the results indicated that The contents of TN,TP,NO₃^--N,NH₄⁺-N and PO₄^--P in the pond water of the experimental group in October 2017,January,April,April,July and October were significantly lower than those in the control group?P<0.05?.The abundance of Zymomonas,Roseomonas,Dechloromonas and Chitinophaga in water of the experimental group was significantly higher than that in the control group?P<0.05?.The abundance of the pathogenic bacteria Pseudomonas,Flavobacterium and Klebsiella in the prokaryotic microorganisms of the experimental group was significantly lower than that of the control group?P<0.05?.Among of these prokaryotic microbial communities,Dechloromonas and Chitinophaga have the function of removing NO₃^--N,Zymomonas and Roseomonas have the function of denitrification.The Chao1 and Shannon index in water of the experimental group were significantly higher than those in the control group?P<0.05?.The main influencing factors affecting prokaryotic microbial communities in water are TN,TP,NO₃^--N,NH₄⁺-N and PO₄^--P.The experimental results confirmed that by adding Bacillus spp to the pond,the structure of the prokaryotic microbial community in the water can be changed,thereby realizing the adjustment of the physical and chemical factors of the pond.In summary,the addition of the exogenous microorganism,Bacillus spp,to the culture pond can change the microbial community structure in the water,increase the microbial diversity,and achieve the regulation of physical and chemical factors in the pond water,thereby reducing the discharge of cultured pollutants.The research results have certain significance for reducing the pollution of aquaculture tail water to the water environment.