Ecological Study Of Micro-organisms In Sediments Of Dishui Lake And Its Diversion River

Dishui Lake, which is located in the southeast corner of Lingang NewCity of Shanghai, is the largest artificial lake on the tide beach. It was dugin June2002, and water was reserved since October2003. The lake isround, with a total area of5.56km2and an average depth of3.7m, and isthe core of water scheduling and the heart of the landscape in Lingang NewCity. The water is mainly derived from the huangpu river, which flows intothe Dazhi river, then goes through the Suitang river, Luchao river, finallyflows into C-gang wailian river, C-gang neilian river, and then the lakeitself.As one of the basic ecological researches on lake, investigation onthe community structure of microorganism in sediments of Dishui Lakeand its diversion rivers was carried out from January2010to October2011.The research could be divided to three stages. During the first stage,sediment samples were collected from the center of Dishui Lake in summer2010, and then the culture-dependent dominant micro-organisms wereseparated, purificated and identificated with Biolog automatic microbiology analysis system to explore the dominate Bacterial colonies’characteristics in sediment of Dishui Lake. During the second stage fromJanuary to December in2010, the distribution of cultivable organicphosphate solubilizing bacteria (OPB) and inorganic phosphate solubilizingbacteria (IPB) in sediments of Dishui Lake and its diversion rivers wasstudied to interpret the role of phosphorus bacteria in material circulationand energy flow. At the same time the correlation between the number ofphosphorus bacteria and total phosphorus (TP), total soluble phosphate(TDP) or active phosphorus (AP) was studied. In2011, We collectedsediment samples from Dishui Lake and its division rivers, analyzed thefunction and species diversity of the microbial community with BiologEcoPlateTM automatic microbiology analysis system to master thestructure and stability of microbial community in Dishui Lake and itsdivision river. The results were listed as following.Results showed that the total number of bacterial colonies in DishuiLake was2.43×10~4CFU/g, less than the other lakes or oceans which hadbeen studied by the former researchers. Gram-negative bacterium made up87.5%of eight bacterial species and among which seven types ofGN-NENT and one type of GP-ROD were identified. The structure ofcolonies in Dishui Lake sediment preferred to rich nutrition, high salinityand alkaline lakes. The eight strains of bacterium were Aeromonas encheleia, Acinetobacter calcoaceticus/genospecies, AeromonasschubertiiDNA group12, Shewanella putrefaciens B, Aeromonasveronii/sobria DNA group8, Vibrio campbelli, Bacillus mycoides andVibrio metschnikovii respectively.The annual average values of OPB and IPB in sediments of diversionrivers in front of the inlet gate were (2.76×10~4±1.31×10~4) CFU/g and(7.19×10~3±3.98×10~3) CFU/g respectively, while in rivers after the gate thevalues were (1.05×10~4±3.56×10~3) CFU/g and (2.54×10~3±8.77×10~2) CFU/g.The annual values of OPB and IPB in sediments of Dishui Lake were(6.69×10~3±2.63×10~3) CFU/g and (1.66×10~3±5.83×10~2) CFU/g respectively.The number of OPB and IPB in sediments of Dishui Lake and its divisionriver sediments was less compared to the former research of the other lakes.Both in Dishui Lake and its diversion rivers, close correlations wereobserved between the amount of OPB, IPB in sediments and phosphorusconcentration in water. OPB, IPB amount had significantly positiverelationship with total phosphorus (TP) and the related coefficients werehigher than that between bacteria and total dissolved phosphorus (TDP) orreactive phosphorus (AP).The microbial community in sediments of Dishui Lake and itsdivision river was active. The maximum AWCD in rivers’sediments infront of the gate, after the gate and in the lake were2.78,2.39and2.38 respectively, which meant the capacity of recovery of the ecosystem fromforeign stress was high. The utility of sugar and its derivatives and aminoacid and its derivatives by microbial community was strong. All the opticaldensity in L-asparagine of microbial community in each sample station wasabove8. The seasonal changes of Shannon-Wiener index in each samplepoint were not obvious which meant function diversity of microbialcommunity was steady. Except the C gang Neilian River and C gangwailian river, the values of Shannon-Wiener index in the other samplestations were all above4.