Construction And Operation Effect Of Internal Circulation Culture System Of Litopenaeus Vannamei

China shrimp culture industry has developed rapidly,and its scale and output have been the first in the world for many years.However,the extensive culture mode restricts the sustainable development of shrimp culture industry.In view of the problems existing in the existing culture mode of Litopenaeusvannamei,this study constructs an internal circulation culture mode of Litopenaeusvannamei.The culture mode makes full use of the space of the culture pool,builds the selected high-efficiency substrate in the culture pool,and uses its biofilm to purify the water quality,so that the culture pool has the dual functions of culture and water quality purification,with small area,simple technology and culture.The pool has the advantages of high utilization rate of space and friendly environment.The main research contents include:(1)screening of efficient substrates;(2)construction and operation effect of internal circulation shrimp culture system;(3)changes of microbial community structure and function in polyurethane biofilm.The conclusions are as follows:(1)select 7 kinds of substrates,such as towel gourd,PVA gel,polyurethane,artificial water grass,PC filter,coral bone and glass fiber as biofilm carrier,and compare their nitrification function.The results showed that the establishment time of nitrification function was related to the properties of matrix materials and the growth characteristics of microorganisms with nitrification function on the surface of matrix.The removal effect of ammonia nitrogen of Luffa complex and coral bone was better than that of other matrices,polyurethane and glass fiber were the second,and the time from degradation of ammonia nitrogen to undetectable was 5d,7d,6d,8d,8d,5d and 6d,respectively.The strength of ammonia oxidation was 1.31 mg/L·d-1·L-1 and 1.2 mg/L·d-1·L-1,followed by polyurethane,1.01 mg/L·d-1·L-1;the time ratio of nitrite nitrogen reduction to no detection was 8d,13 d,10d,16 d,19d,9d,11d;the activity of nitrite oxidation was 2.17 mg L-1d-1,0.87 mg L-1d-1,1.32 mg L-1d-1,0.58 mg L-1d-1,0.39 mg L-1d-1,1.45 mg L-1d-1and 0.91 mg L-1d-1,respectively.The oxidation activity of nitrite in loofah collateral system was the strongest,followed by coral bone and polyurethane.The results showed that the effect of artificial substrate nitrification system was loofah,coral bone,polyurethane,glass fiber >PVA gel and artificial water >PC filter.(2)the nitrification function of each system was enhanced by increasing the initial concentration of ammonia nitrogen in the system step by step.The experiments were carried out in three stages according to the initial concentration of ammonia nitrogen of 20 mg / L,30 mg / L and 40 mg / L respectively to calculate the intensity of ammonia oxidation and the removal rate of ammonia nitrogen in the system for 48 h.After the final establishment of the system,the ammonia oxidation intensity increased by 9.3,6.04,7.56,4.2,4.5,8.46 and 7.39 mg / L · D-1 respectively,and the ammonia nitrogen removal rate increased by 49.2%,50.1%,48.6%,42.8%,40.1%,47.3% and 41.5% respectively in 48 h.The experimental results show that the nitrification capacity of the system can be enhanced by increasing the initial concentration of ammonia nitrogen step by step.(3)two inner circulation culture systems with an effective volume of 2m3 were constructed,and polyurethane matrix was used to control the standard seedlings and water quality of culture experiment of Litopenaeusvannamei.The results showed that the concentration of NH3-N was below 0.15 mg / L,the peak concentration of NH3-N was 0.15 mg / L and the peak concentration of NH3-N was 0.1 mg / L and 0.1 mg / L respectively,all of which were controlled within the safe concentration.The concentration of NH3-N in all the systems increased slowly in the early stage,and the peak concentration of NH3-N in the late stage was 0.89 mg / L and 1.08 mg / L respectively,and the control of substrate on the aquaculture water body was 0.89 mg / L and 1.08 mg / L respectively.In the end of the experiment,the concentration of nitrate in 1 × system was 13.56 mg / L,slightly higher than 11.23 mg / L in 2 × system,and the total phosphorus in each system finally increased,with the final concentrations of 5.11 mg / L and 5.19 mg / L,respectively.In the process,the concentration of total phosphorus in the system first decreased and then increased,which was controlled within a reasonable range.The results showed that the polyurethane matrix had a significant effect on the water quality control of the culture system of Litopenaeusvannamei,and enhanced the nitrification capacity of the culture system,which was conducive to the growth of Litopenaeusvannamei.(4)DNA extraction and high-throughput sequencing were carried out at the end of water culture stage,standard seedling stage and seedling culture stage.In the whole experimental culture cycle,23 gates were detected in the three stages of culture,11 gates were detected in the water stage,18 gates were detected in the standard seedling stage,and 20 gates were detected in the post seedling culture stage.The main dominant phylum in the whole culture cycle are Proteus,Bacteroides,actinomycetes,Fusarium and blastomonas.As the absolute dominant phylum,proteus accounts for more than 50% in all stages of culture.Bacteroides with secondary dominance accounts for 10.27% ? 35.55% in all stages of culture.The dominant phylum species are the same but different in all stages.The different proportion of phylum affects the regulation of water quality and the growth of prawn.In the class level,43 classes were detected in three stages,16,17 and 18 classes were detected in each stage,among which 8 classes were found in total;?-Proteus,bacteroidea,?-Proteus,?-Proteus and actinomycete were the main dominant classes,accounting for over 67% of the total,and in the breeding period,bacillus,blastomonas,xanthobacteria and other classes were also detected.The microorganisms in water also play a positive role in the decomposition of organic matter and the growth of prawn.In terms of genus level composition,there are three groups with nitrification function detected in the whole culture cycle,including nitromonas and nitrococcus with ammonia oxidation function and nitrospirillum with nitrite oxidation function.The proportion of genera with organic matter decomposition and prawn prebiotic effect detected in each stage is different,including blastomonas and microcystins.All or most of them belong to the same genus.