Study On The Dynamic Changes Of Water Quality And Microbial Diversity Of Shrimp(Litopenaeus Vannamei)culture Pond

Litopenaeus vannam is an important economic culture species,the shrimp culture with winter shed is welcomed by the farmers for its anti-season culture due to high economic benefit.The level of water environmental quality is quite relevant to the breeding quality of Litopenaeus vanname.The system composed of physical,chemical and biological factors,and microbial community has important roles.In the study,two Litopenaeus vannamei ponds with winter shed from Longhai Yujiang Co.ltd.were used to determined physical and chemical factors?Temperature,Dissolved oxygen,Ammonia nitrogen,Redox potential,Nitrite,Sulfide,Chemical oxygen demand,Total nitrogen,Chlorophyll a?.The PCR-DGGE?polymerase chain reaction?-DGGE?denaturing gradient gel electrophoresis?was used to detected the diversity of microbial community and the Real-time fluorescent quantitative PCR?RT-PCR?was used to quantify the Vibrio parahaemolyticus.The results were as follows.?1?The mortality showed a positive correlation with HS^-?P<0.05?and a negative correlation with NO₂^--N?P<0.05?.DO and T have no significant correlation with the mortality?P>0.05?,DO is not a limited factor because of suitable management of aerator,T is not an absolute determinant factor in this study,which was influenced by the hoisting of outside air temperature,showed a very negative correlation with NH₄⁺-N,COD and HS^-?P<0.01?,a positive correlation with NO₂^--N?P<0.05?,showed a negative correlation with Chla?P<0.05?.NH₄⁺-N,COD showed correlation with HS^-,NO₂^--N,these factors directly or indirectly effect the growth of shrimp.By adjusting T,decreasing the amount of shrimp bait or installing the oxygen aerator in the pond bottom,to the COD and HS^-could be decreased.?2?According to the results of the DGGE fingerprint,the changes of the bacteria abundance during the whole culture period from high to low was highest in the middle and the late stages?Juanary to February?,final stage of culture?March?,early stage?November to December?,respectively.The DGGE fingerprint sequences are more similar in the close sampling time in the same pond,the two ponds showed no significant difference in microbial diversity?P>0.05?,the Shannon-Wiener index of the DGGE fingerprint were from 1.60 to 2.76during the whole period,and average were 2.20,2.34,respectively.The sequenced result showed that unclassified Bacteria,Cyanobacteria,Alphaproteobacteria,Betaproteobacteria,Proteobacteria and Actinobacteria were dominant microbial in the whole culture period.The RDA analysis indicated that Temperature,HS^-,NH₄⁺-N and NO₂^--N were the main factors influenced microbial community.So factors like Temperature,HS^-,NH₄⁺-N and NO₂^--N should be paid close attention and adjusted it in a suitable range so as to prevent disease outbreaks effectively.?3?The result of Real-time fluorescent quantitative polymerase chain reaction showed that the concentration of Vibrio parahaemolyticus from 1.08×10⁷-1.08×10² copy/2?L is available,the CV of the results for 3 repeats was less than 3%,and the detection limit of Real-time fluorescent quantitative polymerase chain reaction was 1.08×10²copy/2?L,This plasmid was used to develop the PCR method and standard curve equation is y=-2.91791x+38.27743,R²=0.9892.T and NO₂^--N showed very significant negative correlations with the concentration of V.Parahaemolyticus?P<0.01?.TNH₄-N showed a very significant positive correlation with the concentration of V.parahaemolyticus?P<0.01?,while mortality showed a very significant positive correlation with the concentration of V.parahaemolyticus?P<0.01?.HS^-showed a positive correlation with the concentration of V.parahaemolyticus?P<0.05?.