Study On Sediment Microbial Community Structure In Different Model Culture Ponds

Aquaculture pond is a relatively closed and fragile ecosystems, but it is also an ecosystems whicheasy to control. Sediment is an important part of the pond ecosystem, First of all, the accumulation ofsediment in the ponds, on the one hand, it adsorpt the nitrogen, phosphorus and other bio-nutrients of water,the other hand, sediment release a variety of nutrients to the water, deteriorate the water’s dissolved oxygen,increase the incidence of farmed animals’ disease. Therefor, to study the Physic-chemical condition andmicrobe condition of sediment in aquaculture pond has an important meaning for control the environmentand make full use of the material and energy of sediment.1In order to better understand the important role of sediment microorganisms in material cycle andenergy flow of aquaculture pond system, three shrimp (Penaeus vannamei) ponds covered with plasticsheet in the bottom in Henshan, Ningbo were chosen and phospholipid fatty acid (PLFA) analysis methodswere used to investigate the sediment microbial community structure and its relationship withphysical-chemical factors during a three-month period (from June to September,2010). The results showedthat the sediment PLFAs were mainly contributed by the saturated fatty acid, branched fatty acid andmonounsaturated fatty acid; the amount of polyunsaturated fatty acid and cyclopropane fatty acid wasrelatively smaller. The total microbial biomass, bacterial biomass and fungi biomass increased significantlywith culture time. The principal component analysis (PCA) of the characteristic PLFAs in different periodsshowed the total of PC1and PC2explained the composition of sediment microbial community structure of81.4%. Although the majority of microorganisms in the sediment were bacteria, bacteria/fungi ratiodecreased significantly with culture time due to the better adaptation of fungi to the sediment habitat. Theratios of G+/G-bacteria in the latter culture period were smaller compared to the mid-period, but did notchange obviously from later-period to final-period. Redundancy analysis (RDA) showed that the totalmicrobial biomass, bacterial biomass and fungi biomass were significantly correlated with the totalnitrogen and G+bacterium biomass, G-bacterium biomass were significantly correlated with the NO2--N、NO3--N. All of them were negatively correlated with the secchi depth(SD).2Water quality and sediment microbial community structure were examined in two adjacent shrimp(Portunus trituberculatus) ponds with different aeration system during a three-month period from August toDecember2010in Xianxiang, Ningbo, Zhejiang Province. Results showed that the water quality of thepond with submerged aeration systems was better than that of the control pond, like that dissolved oxygenconcentration of the aerated pond was maintained at5mg/L in the breeding cycle while the control pondwas maintained at4mg/L. meanwhile, the ammonia concentration at the aerated pond was much lower thanthat at the control pond. Through the pond sediment microbial PLFA spectrum analysis, the total microbialpond bottom oxygenation throughout the investigation period was significantly higher than turbine pond,and the fungi/bacteria, G+bacteria/G-bacteria ratio is higher than the relative control pond. Use thecharacteristic fatty acid ratio (18:1ω9c/18:1ω9t) to reflect environmental conditions, the results show that:the environment of the pond with submerged aeration systems is better than the turbine aerator pond.3From April to October2011, select four different mode aquaculture ponds from coastal cultivating areas in ningbo zhejiang Province, including the greenhouse-style freshwater shrimp pond, intensiveseawater shrimp culture pond, freshwater oxygenated bottom-style shrimp mixed culture pond, andseawater mud clam and shrimp polyculture pond. The water quality factors, sediment physical andchemical factors, sediment microbial community structure and activity of the end of their breeding werestudied, the results showed: the best water quality of this four differernt mode aquaculture ponds isfreshwater oxygenated bottom-style shrimp mixed culture pond, the worst is intensive seawater shrimpculture pond. due to sediment organic matter content in intensive seawater shrimp culture pond is the most,so microbial biomass, microbial activity, enzymatic activity are the highest, but relative content of thefungus and G+bacteria is the lowest levels. Principal component analysis (PCA) showed that: the firstprincipal component have a greater positive correlation mainly with urease, organic matter content,microbial activity, total PLFA, B/F (r>0.9), and have a greater negative correlation with Gram+/Gram-、pH、18:1ω9C/T、 mono-unsaturated/branched-chain (r>0.9); Second principal components have a greaterpositive correlation with dehydrogenase (r>0.8). Four different type ponds scatter in the PCA diagram,indicating their microbial community structure and environmental conditions have obvious differences.