Research On The Relationship Between Phytoplankton And Chemical Measurement Of Water Factors In The Ponds Of Litopenaeus Vannamei

Litopenaeus vannamei is one of the main varieties of shrimp culture in China because of its thin shell,fat body,delicious meat quality,wide range of suitable temperature and salinity.As a direct environment for the growth of Litopenaeus vannamei,chemical measurement of water and the characteristics of phytoplankton will affect the growth,development yield and quality of Litopenaeus vannamei.In order to study the characteristics of chemical measurement of water factors and phytoplankton community structure and the relationship between chemical measurement of water factors and phytoplankton community structure during the cultivation of Litopenaeus vannamei,this study was carried out in Cooperative Haifeng in Fengxian District,Shanghai.There are 2 seasongs every year,the first season(April 1st-June 9th,2016 and March 16th-May 11 th,2017)are greenhouse cultivation,and the second season(July 27 th – September 25 th,2016 and July 7th-September 3rd,2017)are open-air breeding.Studies on chemical measurement of water include of T,DO,p H,TN,TAN,NO2--N,NO3--N,TP,AP,Chl-a and CODMn.The chemical measurement of water samples were collected every 5 days,and the samples for phytoplankton were collected every 15 days.After sampling,the changes of chemical measurement of water factors were tested,and phytoplankton community structure characteristics were analyzed by species,biological density,diversity index and dominant species.The main research results of this study are as follows:1.It was found that all the chemical measurement of water factors were suitable for the growth of Litopenaeus vannamei in four seasons of two years.In 2016 and 2017,the concentration of TP and AP remained low,and in every season,Chl-a was lower at the early stage of culture and then increased;Comparing the second season(outdoor culture)with the first season(greenhouse),we can find that T and p H.TN,TAN,TP and Chl-a increased,while NO3--N and NO2--N decreased slightly.2.According to?Freshwater pond aquaculture water discharge requirements(SC/T9101-2007)?,p H and TP reached the first level standard.In the second season of 2016,50% of the ponds reached CODMn second level,the others are all first level standard.In 2016,25% of the ponds super TN second level standard in first seson,33% of the ponds in second season.In 2017,57% of the ponds super TN second level standard in second season.Due to the fact that a lot of feeds,nutrients and organic matter were accumulated during the breeding process,there was a phenomenon of over standard nitrogen content in aquaculture effluent.3.In the two seasons of 2016,there were 7 phylum,10 class,20 order,30 family,59 genus and 113 species of phytoplankton.In the two seasons of 2017,there were 4 phylum,6 class,15 order,23 family,44 genus,113 species were identified.From the number of species,Chlorophyta> Bacillariophyta > Cyanophyta > Euglenophyta > Xanthophyta > Chrysophyta > Pyrrophyta,common species of phytoplankton in culture ponds are Chlorophyta and Bacillariophyta.The diversity index of Shannon-Wiener was from 0.21 to 3.85,the diversity index of Margalef was 0.12 ~ 2.18,and the uniformity index of Pielou was 0.10 ~ 0.97.The species diversity index and evenness index of the phytoplankton in Litopenaeus vannamei Cultured ponds were in the normal range.In 2016,we identified 18 dominant species(including 3 undetermined species),8 Chlorophyta,8 Cyanophyta and 2 Bacillariophyta,with the highest dominance of Merismopedia minima(0.76).In 2017,24 species(including 3 undetermined species),15 Chlorophyta,5 Bacillariophyta,3 Cyanophyta and 1 Euglenophyta,the highest dominance was Chlorella ellipsoidea(0.4).In the ponds of Litopenaeus vannamei,Chlorophyta,Bacillariophyta and Cyanophyta are easy to become dominant species.4.According to the correlation analysis of phytoplankton dominant species and chemical measurement of water factors,it was concluded that hlorophyta is mainly affected by p H,nitrogen(including ammonia nitrogen,nitrate nitrogen,nitrite nitrogen),Cyanophyta by phosphate(including total phosphorus and active phosphorus),and Bacillariophyta by temperature,so we must pay more attention to temperature,p H,nitrogen and phosphate.