Effects Of Different Polyculture Modes Of River Crab On Physical And Chemical Factors And Microbial Community Structure In Ponds

Crab farming is an important part of my country’s aquaculture industry.However,traditional pond farming models have problems such as high-density farming,waste of water resources and easy environmental pollution.It is necessary to continuously improve farming techniques and farming models,adjust the farming structure,and improve crab farming.Model ecological sustainable development,so as to better realize ecological,economic and social benefits.As an important part of the aquaculture ecosystem,water bodies and sediments,studying the changing laws of their physical and chemical factors and the diversity of microbial communities are of great significance to further improving the aquaculture ecosystem.In this study,the polyculture model(MC)of river crab green prawn and the polyculture model(PC)of river crab-mandarin fish and blue prawn were used as the research objects.The experimental period was from August 7th to September 27 th,2020,with a total of four samplings.Collect water and sediment samples,partly for the determination of physical and chemical factors,and partly for the determination of the microbial flora structure.Measure the temperature,p H,dissolved oxygen,ammonia nitrogen,nitrite nitrogen,ammonia nitrogen,nitrate nitrogen,and nitrite nitrogen in the bottom sludge.The results of microbial flora in pond water and sediments were determined by high throughput sequencing method.The main findings are as follows:(1)In terms of physical and chemical factors,the water environment of the PC model is better than that of the MC model,and the sediment environment of the MC model is better than that of the PC model.The content of ammonia nitrogen and nitrite nitrogen in the MC model water body was significantly higher than that in the PC model(P<0.05),and the content of ammonia nitrogen and nitrate nitrogen in the MC model in the sediment was significantly lower than that in the PC model(P<0.05);(2)In terms of microbial diversity,in the sampling on August 28,the microbial diversity of the water in the MC model was higher than that of the PC aquaculture model;in the sampling on September 27,the microbial diversity of the bottom mud of the MC aquaculture model was higher than that of the PC aquaculture model.In the sampling on August 28,the shannon index in the MC model water body was significantly higher than that in the PC model(P<0.05),and the simpson index was significantly lower than the PC model(P<0.05);in the sampling on September 27,the MC model sediment The CHAO index and Shannon index were significantly higher than the PC model(P<0.05);(3)In terms of microbial dominant flora,the dominant bacteria phyla in MC model water are Proteobacteria(>44%),Bacteroidota(>21%),Actinobacteria(>12%)and Firmicutes(>12%),the dominant bacteria are Flavobacterium(>11%),Exiguobacterium(>10%),Brevundimonas(>10%),Acinetobacter(>7%);the dominant bacteria phyla in PC model water are Proteobacteria(>44%),Bacteroides(>29%),Firmicutes(>12%)and Actinomycetes(>9%),the dominant bacteria are Flavobacterium(>18%),Brevundomonas(>12%),Exiguobacterium(> 11%)and Acin-etobacter(>10).The dominant bacteria phyla in the bottom mud of MC mode are Proteobacteria(>16%),Unclassified(>14%),Chloroflexi(>11%)and Bacteroides(>10%);The dominant bacteria phyla in the bottom mud of PC model are Proteobacteria(>16%),Unclassified bacteria(>15%),Bacteroides(>10%)and Chloroflexus(>10%).The abundance of denitrification bacteria in the water of PC mode is higher than that of MC polyculture mode.The Bacteroides and Flavobacterium in the MC model water were significantly lower than those in the PC model(P<0.05).