The Effects Of Long-Term Shrimp Aquaculture On The Soil Quality Monitoring By Soil Microbial Communities And Activities

With the rapid expanding of shrimp aquaculture, upland ponds have been built extensively along the coast. In order to evaluate the influence of shrimp aquaculture on soil quality, soil samples were collected from two typical sites, Baimajing and Dongjiao of Hainan island, respectively. A combination method had been used to monitor soil community composition and microbial activity by employed fatty acid methyl ester (FAME) analysis, PCR-denaturing gradient gel electrophoresis (DGGE), microcalorimetry and soil enzyme activities.The most remarkable chemical property was high salinity and unbalance nutrients in upland pond soils. The culturable bacteria, fungi and actinobacteria decreased significantly (P< 0.05). The fatty acid of fungi and actinobacteria also declined in upland pond soils, which indicated they were sensitive to the high salinity (P< 0.05). Microbial diversity in upland pond soils also decreased presenting by Shannon-Weaver index from DGGE, and the bacterial community composition changed a lot.β-Proteobactera and Acidobacteria dominated in native soils, butγ-Proteobactera and Firmicutes were the main class in upland pond soils. And some communities playing important roles in ecosysterm disappeared in upland pond soils.Furthermore, three enzymatic activities (dehydrogenase, urease, and acid phosphatase) decreased significantly (P< 0.05). The high salinity would inhibit the metabolism of soil microbes, which also demonstrated by total heat output (QT) negative correlating with K and Mg (P< 0.05). A higher dissipation of heat per cell unit was observed in upland pond soils than native soils, indicating a less efficient metabolism of soil microbes in upland pond soils. Moreover, acid phosphatase positively correlated with the peak power (Pmax) (P< 0.01) and negatively connected with heat dissipation per cell unit (QT/N0) (P< 0.05). These results showed that the soils were degraded after long-term shrimp aquaculture. Qt/No,tmax, soil enzyme activity and DGGE Shannon-Weaver index (H) were all good indicators for evaluating soil qulity.