Study On Water Environmental Impact Of Shrimp Farming In Shanghai Suburbs

In order to study the environmental quality of the source water around the shrimp farms in the suburbs of Shanghai,relevant surveys were conducted on 17 farms in Fengxian District,Jinshan District,Qingpu District and Chongming District of Shanghai.Using"Surface Water Environmental Quality Standards"and comprehensive water quality pollution index,the water quality of 17 shrimp farms in 4 districts of Shanghai was evaluated.The 72 sampling data showed that the comprehensive pollution index of the collected source water was greater than 1,which was at the pollution level.The p H range of 98.61%of the incoming water source water is between 6.0 and 9.0,which meets the aquaculture water standards.38.89%of dissolved oxygen meets Class III standards.52.77%ammonia nitrogen meets Class III standards.47.23%of the total phosphorus meets Class III standards.62.51%of the chemical oxygen demand meets Class III standards.The total nitrogen in the source water of the 16 farms in the 4 districts exceeded the standard.The proportion of total nitrogen that was inferior to the class V was 97.22%.In the aquaculture process,the dissolved oxygen,ammonia nitrogen,total phosphorus,chemical oxygen demand,and total nitrogen in the source water need to be pre-treated for aquaculture.During the breeding process,attention should also be paid to the regulation of total nitrogen in water.In order to study the possible impact of shrimp aquaculture wastewater on the surrounding environment,take a shrimp farm in Shanghai as an example.Continuously monitor p H,total nitrogen?TN?,total phosphorus?TP?,and chemical oxygen demand(COD_Mn)in the discharge channel of the farm.Shrimp farming wastewater was evaluated using"Water Discharge Requirements for Freshwater Pond Farming".142 measurements at 8 sampling points in the drainage channel show:The p H of all the discharged water meets the secondary discharge standards of the"Water Pond Aquaculture Water Discharge Requirements"?SC/T 9101-2007?,and even 97.18%of the discharged water meets the primary discharge standards;total nitrogen met the secondary standard,of which 88.03%met the primary standard;70.42%of the total phosphorus met the primary standard,26.77%met the secondary standard,and 2.82%did not meet the secondary emission standard;For chemical oxygen demand,69.01%of the discharged water meets the first-level standard,29.58%meets the second-level standard,and 1.41%of the discharged water does not meet the second-level discharge requirement.During the breeding process,further control of total phosphorus and chemical oxygen demand is needed.Ensure to meet the requirements for aquaculture water discharge and reduce pollution in the waters surrounding shrimp farms.In order to study the water quality change pattern of the pure Litopenaeus vannamei model and the mixed cultivation model of Litopenaeus vannamei and Macrobrachium rosenbergii.Explore the difference in water quality between the two aquaculture models,and conduct it in a shrimp farm in Shanghai.Four ponds were selected for comparison experiments.Sampling is started when the shrimp fry are put into the pond for breeding,and the sampling is finished after the shrimp has grown to the commercial specifications after exiting the pond.The collection and preservation of water samples in the pond are in accordance with HJ/T 91-2002.The sampling time of the water sample,local weather conditions,water color of the breeding pond are recorded on site,and the water temperature,dissolved oxygen?DO?and p H are measured on site.Laboratory testing included total nitrogen,ammonia nitrogen,activated phosphorus,nitrate nitrogen,total phosphorus,nitrite nitrogen,chemical oxygen demand and chlorophyll a.The comprehensive pollution index method was used to analyze the pollution situationg of each shrimp pond under two different culture modes.The results show that the trends of water temperature in each breeding pond are basically the same under the two different breeding modes,which are closely related to the local weather.The changes in p H were basically the same,and both met the growth needs of Litopenaeus vannamei and Macrobrachium rosenbergii.The changes of total nitrogen,active phosphorus,ammonia nitrogen,nitrite nitrogen,nitrate nitrogen,total phosphorus,chemical oxygen demand and chlorophyll concentration all showed different changes.This is mainly related to factors such as feed,weather factors?rainfall,air temperature?,use of water quality regulators?EM bacteria,etc.?and behavioral methods of breeding production management during the breeding process.Using the comprehensive water quality pollution index analysis,it was found that under the polyculture mode of Litopenaeus vannamei and Macrobrachium rosenbergii.the average integrated pollution index value of ponds?0.62?is lower than that of pure Litopenaeus vannamei farming model?0.75?,indicating that water quality is better in polyculture mode.Water quality analysis and virus detection was carried out in order to understand the correlation between water quality and diseases occurrence of Litopenaeus vannamei.The experiment was carried out at a shrimp farm in Shanghai.Combined with situation of disease occurrence,principal component analysis?PCA?and orthogonal projections to latent structures discrimination analysis?OPLS-DA?were used to figure out the difference of water quality among healthy group,virus carrying group and diseased group,and find those water quality factors that contributed most to the differences among three kinds of groups.In this research,Shrimp hemocyte iridescent virus was detected in some shrimp samples and the results showed that:?1?Obvious water quality difference existed between diseased group and healthy group,also between diseased group and virus carrying group.While no obvious difference was found between healthy group and virus carrying group,once no disease outbreaks.?2?Total nitrogen,temperature,total phosphorus and dissolved oxygen were main water quality factors reflecting the occurrence of shrimp disease.?3?It's likely that mechanical operations such as diversion might induce shrimp disease.In summary,water quality conditions including water temperature,etc.,should be paid attention to during the breeding of Litopenaeus vannamei and unnecessary mechanical operation activities should be reduced.