Research On Water Quality Factors And Aquatic Organism In Litopenaeus Vannamei

In order to study the correlation of the variation characteristics of water quality factors, the changes of phytoplankton community structure and microbial biodiversity during Litopenaeus vannamei culturing, to explore the relationship between water quality factors and disease occurs of the prawn, to reveal the water quality environment for the healthy growth of the prawn, research on water quality factors and aquatic organism in Litopenaeus vannamei culturing ponds was done in Haifeng farming cooperatives, Fengxian district,Shanghai during 2014-2015. The experiment was divided into three stages: the first stage was the second crop farming in 2014(July to October, 2014), the second stage was the first crop farming in 2015(April to June, 2015) and the third stage was the second crop farming in 2015(July to September, 2015), the first and third stages for the open-air breeding, and the second stage for greenhouse cultivation. Water quality factors were tested in three stages and variation of water quality factors were analyzed, as well as the principal component analysis of the water quality factors between the incidence ponds and normal ponds was done. The change of the microbial community structure was also tested in the water and sediment in culturing ponds, and analyzed the correlation combined with water quality factor in the second stage. Adding monitoring phytoplankton and analysis of the correlation between changes of phytoplankton community structure and environmental factors were done in the third stage.The main results and conclusions are as follows:1. All the TN and TP were higher than the required values for aquaculture while TP exceeding rate was the most serious. TP exceeding rate were as high as 100.4% and 297.6%, and the TN exceeding rate were 5.3%and 32.% in the first and second crop farming in 2015. Through the analysis of ammonia nitrogen(TAN) and nitrite nitrogen(NO2--N) in the first crop and second crop water in 2015, it was concluded that the, TAN and NO2--N were low in second crop farming,mean respectively were 0.55mg/L and 0.05mg/L, done not affect the health of shrimp.The content of nitrite nitrogen appeared jump point type growth in the middle of culture in first crop farming, and improved to higher than 0.3mg/L in later stage, and outbreak of disease. It speculate that high temperature, high stocking density and poor air exchange were reason of the rise in the content of nitrite.Comprehensive analysis showed that nitrite nitrogen is the main reason caused the difference of water quality factor in incidence ponds and normal ponds in three quarters, and nitrate nitrogen is higher, the greater the risk of the disease, followed by nitrite nitrogen and temperature. Organic matter and total phosphorus is linked to the water environment in incidence ponds of negative regulating, namely, within a certain range of high levels of organic matter and total phosphorus, can maintain water stability and have important effect on prawn healthy growth. Total nitrogen, reactive phosphorus and pH have little influence on the water quality factor in incidence ponds.2. To survey the phytoplankton in aquaculture water, a total of 6 phyla and 100 taxa of planktonic algae were recorded, and the primary phyla were Chlorophyta, Cyanophyta and Bacillariophyta. The total dominant species were 6 species, with chlorophyta species most, and they were all common algae in water, no sewage type of algae was found. Chlorophyta and Bacillariophyta is of absolute advantage during the whole breeding cycle, which Cyanophyta content is not high. Along with the phytoplankton biomass increased significantly, and showed a steady upward trend. Multi biodiversity is in â…¢ and â…£ grade, with rich diversity of phytoplankton, indicating that the overall quality of aquaculture water is better and more stable. It found that phytoplankton biomass and density in nutrient-rich water are less affected by the nutrient, while temperature is the major factor on phytoplankton community structure in the analysis of phytoplankton community structure and environment factors. Quality of phytoplankton community composition has an important role to stabilize the water ecological environment and also is reliable guarantee of shrimp in open-air breeding farming.3. To survey the microorganism in aquaculture water and sediment, a total of 11 phyla of microbes were identified in aquaculture water, and 13 phyla in sediment. Proteobacteria and Bacteriodetes are the main phylum.The proportion of chlamydia in water increased significantly with the passage of culture time and can cause the disease of prawn. Similarity between samples is small in the whole experiment, rapid microbial succession and poor water stability. 6 microorganism dominant species were identified in aquaculture water, while Pseudomonas aeruginosa as the absolute dominant species with the ratio over 60% in late culturing, speculated that the existence of a large number of Pseudomonas aeruginosa is the main cause of prawn disease. 5 microorganism dominant species were identified in sediment, while Bacteroidetes as the absolute dominant species with a lower proportion. Extreme advantage of microbe species does not appear, indicating that microbial community structure is stable in sediment, not the major factor in causing shrimp disease. Correlation analysis of the microbial community diversity and water quality factor obtained that temperature are the main factors influencing the changes of microbial community structure in the nutrient-rich environment. High temperatures can make microbial growth accelerated metabolism speeding up, and also the decomposition of organic matter and the use of dissolved oxygen in water. It is not conducive to the stability of water bodies. And high temperature also makes the Pseudomonas aeruginosa secrete extracellular substance, which can cause algae dead and deterioration of water quality. Therefore to pay attention to the breeding density in greenhouse cultivation, control temperature and do a good job in the exchange of air in greenhouses.