| Planktonic bacteria are not only of large amount, but also play important role during the process of organic matter degradation and nutrient recycle, therefore, they are important component of aquatic ecosystem. Eutrophication may affect aquatic bacteria community significantly. However, due to the lack of continuous research, the succession law of bacteria community changing along with eutrophication and its influencing factors are still not clear. Based on the investigation from May of2009to April of2010, this observation used CFU (colony forming units) for further research on the temporal and spatial variation feature of aquatic planktonic bacteria in Dianchi Lake.30sampling positions were set, and4areas were divided based on water quality and location characteristic. Water samples were collected once every month lasting for12months from May2009to Apr2010. The emerging bacteria were identified to the species through16S rDNA molecular identification. Furthermore,5dominant bacteria were screened out according to amount of bacteria and frequency of occurences, their adsorption for heavy metal lead and cadmium and the toxic effect to the tested bacteria were studied. All bacteria were cultured under pH8.0,25℃, shaked with90r/min,9%of bacteria were inoculated.The result indicated that:(1) Bacteria quantity in Caohai area increased obviously in Dec2010, ones in Aug, Sep, Dec2010and Apr2011were significantly higher than other months in the north of Waihai area, ones in Dec2010and Apr2011were significantly higher than other months in the middle of Waihai area, ones in Jan, Apr2011were significantly higher than other months in the south of Waihai area; Obviously, bacteria quantity of Dianchi Lake decreased geographically from north to south; Margalef species richness index decreased remarkably from north to south, but there was no change in Shannon-Wiener index, Pielou evenness index and Simpson index.(2) The aquatic bacteria in Dianchi Lake could be divided into15genus, Brevundimonas, Sphingomonas, Pseudomonas and Pedobacter were dominant, and their community structures were relatively steady compared to last annual data. Moreover, bacteria quantity and community structure were influenced by external input, and among them, Brevundimonas were external bacteria. The community structure of aquatic dominant bacteria in Dianchi Lake is generally similar to eutrophic lakes in China and abroad. Proteobacteria and Bacteroidetes are dominant, there is just a little difference in the proportion of bacteria group.(3) Biomass of5bacteria decreased remarkably treated with Pb2+of80mg/L or Cd2+of4mg/L. The adsorbability for Pb2+of the5bacteria could be sequenced as Y2> R7> Y21> R5> Y15. The adsorbability for Cd2+of the5bacteria could be sequenced as Y21> Y2> R7> R5> Y15. With the increasing of metal ion concentration, the adsorption rate for Pb2+and Cd2+of5bacteria was constantly increasing in the beginning but decreased significantly later. The adsorbability increased to some extent along with the increasing of metal concentration, which may be related with the concentration of metal ion. The higher metal ion concentration is, the higher possibility that metal ions may react with biosorbents. The higher ion concentration would aggravate the collision between metal ion and adsorbent, which could lead to more adsorption. The adsorption rate decreased under higher concentration, the reasons could be:①The adsorption rate of bacteria may be related to biomass of bacteria, excessive metal ion inhibited the growth of bacteria and decreased the amount of combining sites;②the total adsorption increased along with the increasing of metal ions in system, but due to the lower increasing rate than the total metal ions'increasing, the adsorption rate showed decreasing.(4) This research could provide basis on studying the environmental effects of bacteria adsorption for heavy metal in the lake ecosystem and the control of polluted water containning heavy metal. |
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