Analysis Of Bacteria Community Diversity In Bioflocs And Bioflocs Contribution To Water Quality In Tilapia And Koi Aquaculture

With the increasing demand of aquatic products,aquaculture has developed rapidly in recent years,for example,the breeding density is growing and the aquaculture model has been changed into extensive and intensive farming.However,many shortcomings of this aquaculture expansion have occurred,such as eutrophication,excess drug,disease infection and other problems.In traditional aquaculture,aquatic farming animals obtain nutrition from the protein of feed,but not 100%absorption,and some of them will release into the water in the form of ammonia,nitrite nitrogen and nitrate nitrogen.In addition,the excrement of the animal coupled with the metabolism of microorganisms also makes the water eutrophication.Hence,it is very important to find a sustainable healthy fanning technology.Biofloc technology is a kind of ecological breeding aquaculture technology due to its purify water quality.It has many advantages including excellent purifying water quality,low production cost and zero water circulation.Bioflocs is a reunion formed by biological flocculation which consists of different substances including bacteria,fungus,phytoplankton and residual bait.Adjusting the ratio of carbon and nitrogen of the water environment,and aerating the water continually and thoroughly could promote the growth of heterotrophic bacteria that use ammonia as nitrogen source.In addition,the particulate matter formed through flocculation in the process could be reused as bait to feed animals,and then that can purify water.The results show that this method not only can purify the water environment and reduce the cost of the feed but also decrease the quantity of exchanged water and achieve zero water exchange recycle.What kinds of microorganisms are in the bioflocs?What are the dominant bacteria,and what are the functions of the bacterial communities in animal aquaculture?Whether bioflocs can play an effective role in large and high-density aquaculture and achieve zero water circulation?These questions will all be the focus of this study.The article does the analysis mainly on bacterial community structure diversity in bioflocs,and explores the dominant bacteria community which may play a major role in the water purification of bioflocs.Tilapia and Koi carp fish were used for elementary experiments and based on the result of laboratory research,and we attempted to explore the effect of purifying water with bioflocs.Therefore,this paper is divided into three parts as follows:(1)Analyze the microbial diversity of different microbial cultivation bioflocs for exploring the main groups of bacteria in bioflocs and finding out the dominant bacterial community.The experimental results show that the dominant bacterial community structure of bioflocs including Proteobacteria,Bacteroidetes and Actinobacteria.The more important heterotrophic bacteria are Alphaproteobacteria?Betaproteobacteria?Gammaproteobacteria?Cytophagia.(2)Explore the effects of different carbon sources and proportion of C/N on the water purification effect of bioflocs.And the experimental results show that the bioflocs inhibit the increase of nitrogen and phosphorus contents,indicating that the bioflocs indeed can play an important role in water purification.The effect has a direct relationship with the amount of glucose added.When the total amount of glucose added is 50%of the feed,purification effect is the best.However,when the total amount is 120%of the feed,the bioflocs could not purify the water,what is worse,it makes the water eutrophication more easily.When the C/N ratio is 25:1,the total nitrogen removal effect is the most obviously,and the total nitrogen concentration can be reduced to only 0.8mg/L.When the C/N ratio is up to 20:1,the total phosphorus effect is the best,and it can be reduced to below 0.3mg/L.(3)Breed the Tilapia and Koi fish under the addition of bioflocs.The experimental results show that the biofloc technology can be applied to large-scale fish farming.Cultivation of stable bioflocs that put into pool can reduce the content of ammonia nitrogen and nitrite nitrogen effectively.Additionally,the growth excrement of fish can promote the growth of bioflocs,and the bioflocs can be used as active bait for fish in return.However,the density and temperature are the significant factors for ammonia nitrogen removal and inappropriate density and temperature could make an impact on the growth of fish.