Study On The Regulation Of Aquaculture Water Of Penaeus Vannamei By Probiotics-biofilm System

The production and scale of shrimp aquaculture in China ranked first in the world,but there were still serious problems of sustainable development,which increased the incidence of various diseases year by year.Pond aquaculture has been the main breeding mode of prawns for a long time in China,mainly in extensive form.Aiming at the shortcomings of the pond farming methods,circulating water aquaculture system model?RAS?was considered to be an friendly environmental mode of breeding,but RAS was difficult to have a large promotion because of the limit by high investment,operating costs and technical requirements.By adding organic carbon source and regulating C/N ratio and increasing the number of heterotrophic bacteria in aquaculture water,biofloc technology?BFT?could regulate quality of aquaculture water and reduce feed coefficient by microbe assimilation of inorganic nitrogen,but the complexity of technical operation and instability limited the use of BFT in practical production.In recent years,the combination of biofloc technology and biofilm has been developing.Biofilm could purify aquaculture water and adsorb floccules particles,which reduced its deposition to the bottom.At the same time,biofilm could reduce feed coefficient by shrimp feeding.But there are also some problems such as few and expensive commercial matrix materials,processing time and so on,which limited its application.Aiming at the existing problems of shrimp breeding,the study invented and researched a circulating shrimp farming system.Fully considering the living space and life habits of shrimp,the system added recycled biofilm carrier and probiotics in breeding water,which could remove toxic materials such as ammonia and nitrite quickly.The system had a double function,including shrimp farming and water quality purification.The main contents of this research included:?1?The effects of three microecological preparations of nitrifying bacteria,bacillus subtilis and photosynthetic bacteria on the conversion process of nitrogen in bait;?2?Six biofilm systems were established using microecological preparations and artificial vectors?pills and ceramics?.The beginning process of system and regulation of water quality were studied in this period;?3?The structure and function of microbial community in biofilm were analyzed by using high-throughput sequencing method.The following conclusions are obtained:?1?There were differences between conversion process of nitrogen in shrimp bait from different microecological preparations.Bacillus could accelerate the ammoniation of organic nitrogen in bait but had no significant conversion effect on ammonia nitrogen and nitrite nitrogen.The concentration of ammonia and nitrogen in single/double dose was increased to 10 mg/L and 20 mg/L respectively.Nitrifying bacteria could not decompose organic nitrogen directly but the conversion effect of ammonia nitrogen and nitrite nitrogen was better.The concentration of ammonia nitrogen and nitrite has been always maintaining at 1 mg/L and 5 mg/L during the experiment.Photosynthetic bacteria had different effects on organic and inorganic nitrogen.The results showed that the conversion efficiency of nitrobacteria and bacillus was better than any one of them.The concentration of ammonia nitrogen and nitrite increased at first and then decreased.Peak concentration of single/double dose was 7.84 mg/L,10.55 mg/L and 10.71 mg/L,15.69 mg/L.?2?Adding artificial carrier could improve efficiency of ammonia and nitrite purification of the system in the process of nitrification system.The purification effect of the pills system was better than that of ceramic in the case of adding the same bacteria.Photosynthetic bacteria could improve the purification efficiency of the system.Intensity of ammonia oxidation in added photosynthetic bacteria system was0.21 mg/L·d^-1 higher than that in non-added system.Removal rate of ammonia nitrogen in 24 hours in added photosynthetic bacteria system was 1.61%higher than that in non-added system.In addition,intensity of ammonia oxidation was increased by 1.91,1.83,2.10,2.18,2.76,2.85 mg/L·d^-1 and removal rate of ammonia nitrogen in 24 hours was increased by 12.74%,11.25%,13.95%,15.21%,17.25%,17.65%respectively after the establishment of nitrification system.?3?The concentration of ammonia and nitrite were maintained at 0.20 mg/L and0.15 mg/L.It had little fluctuation during shrimp aquaculture.The concentration of nitrate nitrogen showed a slow upward trend and had no significant difference;Vibrio control system is effective,total number of Vibrio was maintained at 2.0×102CFU/m L.The Vibrio control performance of pill system is better than that of ceramics in the case of the same bacteria.The control performance of the three-combined bacteria was better than that of two-combined bacteria in the same case of substrate.?4?The microbes were distributed in 32 phyla.The dominant phylum were Proteobacteria,Planctomycetes,Bacteroideses,Actinobacteriaand Gemmatimonadetes.Proteobacteria accounted for more than 40%.There were five species with nitrification function,including Nitrosomonas aestuarii,Nitrococcus mobilis with ammonia oxidation and Nitrospira moscoviensis,Nitrospira lenta,with nitrite oxidation.There were 6 common species in each system,which account for1.08%,1.69%,2.43%,1.32%,2.18%and 1.25%respectively.The species with organic matter decomposition and beneficiation were different and accounted for different proportions.Algisphaera agarilytica,Gemmatimonas phototrophica and Paucibacter toxinivorans were common species in each system.