Enzyme Activity And Functional Microbial Community Structure In Sediment From Lakes And Reservoirs

In lake and reservoir ecosystems,the enzymes of sediments plays an important role in driving the energy flow and material cycling,while enzymes can be used as an indicator to evaluate the nutrient level and microbial activity.In order to investigate the enzyme activity and functional microbial structure of sediments in lake and reservoir,samples were collected over five urban lakes including Beixiu park,Shangyashan,Heilongjiang Province(HLJ),Beijing Botanical Garden(BJ),Qujiang park,Xi'an,Shanxi province(XA),Xuanwu lake,Nanjing city,Jiangsu province(NJ),and Litchi park,Shenzhen,Guangdong province(GD),Lijiahe reservoir and Jinpen reservoir.The diversity of functional microbial in the sediments of the lake was diagnosed using high-throughput DNA sequencing technology and BIOLOG method based on the physical and chemical properties and enzyme activities of the sediments,revealing the coupling mechanism of enzyme activities and functional bacterial diversity in the sediments of the lake.The regulation of enzyme activity in reservoir sediment by artificial induction system was explored to provide theoretical support for controlling endogenous pollution in lake and reservoir.The main research results were as follows:(1)Five urban lakes had serious organic nitrogen pollution.There were significant differences in the enzyme activities among the lake sediments in different cities(P<0.01).T he organic matter was significantly correlated with alkaline phosphatase activity,urease activity and sucrase activity.According to the result of BIOLOG,the carbon metabolism of the sediment bacterial populations was varied with the order of GD>BJ>NJ>HLJ>XA.Carbon metabolism activity was significantly positively correlated with dehydrogenase activity(r=0.851).Principal component analysisshowed that the metabolic capacity of NJ and BJ had little difference,while that of GD and XA had significant difference.(2)The concentrations of organic matter and nutrient salts in the surface sediments of Lijiahe reservoir were relatively high,and the alkaline phosphatase acticity,urease acticity,dehydrogenase acticity and sucrase acticity were spatially heterogeneous.DNA sequencing showed that Sigarispora(4.15%),Trichoderma(2.13%)and Pseudeurotium(1.93%)were the dominant bacteria.According to the redundancy analysis,dehydrogenase activity in the sediments was positively correlated with Mucoromycota,Basidiomycota and Ascomycota.Organic matter,total nitrogen and iron were positively correlated with Zoopagomycota,and organic matter was the dominant environmental factor affecting enzyme activity and fungal community.(3)The total nitrogen,total phosphorus and organic matter in the sediments of Jinpen reservoir were enriched in the surface layer,and showing a decreasing trend in the vertical section.The seasonal difference of enzyme activity was significant(P<0.01),and the enzyme activity decreased with the increase of depth.The results of DNA sequencing showed that the bacterial abundance in the reservoir sediment in July was higher than that in March,and the bacterial population abundance increased with the increase of depth.Firmicutes,Proteobacteria,Bacteroides and Chlorobacteria were the dominant microbe,and Lactobacillus and Bacillus were the dominant genus.The redundancy analysis showed that sucrase activity,urease activity,alkaline phosphatase activity and demineralization had significant effect on Cyanobacteria and Verrucomicrobia.(4)During the operation of the artificial induction system(water lifting aerator),the content of total nitrogen decreased by 2.08%,the content of total phosphorus,iron and manganese increased by 1.71%,16.29% and 19.97%,respectively,and the content of organic matter decreased significantly by 53.19%.The enzyme activities of surface sediment during operation was significantly higher than that before operation,and the urease activity,sucrase activity,alkaline phosphatase activity and dehydrogenase activity increased by 12.85%,44.30%,34.47% and 29.96%,respectively.Four kinds of enzyme activity decreased vertical profile.Total nitrogen,total phosphorus and organic matter were significantly related to the activities of the four enzymes.The operation ofthe system can release the nitrogen and phosphorus in sediment,reduce the content of organic matter and enhance enzyme activity effectively.(5)Cable bacteria are important functional microorganisms involved in sulfur cycling in sediments.In the previous study had shown that cable bacteria belong to Desulfobulbaceae,and the phylogenetic classification of the genus is not yet clear.In this study,fluorescence in situ hybridization was used to preliminarily construct a detection method for cable bacteria,and specific probe DSB706 was selected for hybridization,and it was found that cable bacteria existed in sediments.