Effects Of Sediment Resuspension As A Disturbance On Bacterioplankton Community Composition And Diversity

It is known that bacteria with various community structure play an extraordinarily important role in the heterotrophic foodweb, because the microbial community is the foundation of biogeochemical cycles. On one hand, bacteria decompose organic matter to obtain energy for their living (act as consumers); on the other hand, bacteria are important processes in the degradation and transformation of the dissolved organic matter into particle organic matter. This process was defined as second production (act as producers). However, because it is difficult to culture most bacteria in environmental samples, culturing approaches show us only the tip of the iceberg in regard to the genetic diversity and complexity of microbial communities. Molecular techniques has been used in ecological studies widely, especially since the cultivation-independent methods used in microbial ecology studies which made great progress of the traditional microbial ecology and extended the scope of microbial ecology from cultivated microbes to all life type. So that the theories of microbial ecology closer to its natural essence.In this thesis to determine the response of bacterioplankton community to sediment resupsension we set up two different intensities of the sediment resupsension in experimental microcosms. In the first place we employed the denaturing gradient gel electrophoresis (DGGE) and terminal restriction fragment length polymorphism (T-RFLP) two important and frequently used tools to characterize the bacterial community structure and their related key environmental parameters. Secondly three clone libraries were constructed to investigate the taxa within the bacterioplankton assemblages, in order to analysis of different resupsended processing the main type of bacterioplankton. Finally we employed T-RFLP approach to characterize the bacterial community composition in enclosures during bioremediation experiments in the lake Taihu. Through the database phylogenetic assignment tool (PAT) comparison, revealed a major species of bacterioplankton assemblages of ecological restoration areas. The dynamic changes of bacterioplankton community composition with environmental factors in multivariate statistical analysis, reveals the the impact of the various ecological restoration areas bacterioplankton community composition of the dominant environmental factors. The main results as followed.1. The result demonstrated that the species richness of the bacterioplankton in the treatment with sediment resuspension was higher than that in the controls without sediment resuspension. The bacterioplankton species richness and community diversity in the treatment with weak sediment resuspension (WR) was higher than that with strong sediment resuspension (SR). The relationship between bacterioplankton and environmental factors were investigated using canonical correspondence analysis (CCA) and redundancy analysis (RDA). The CCA and RDA results showed that there was a high degree of correlation between bacterioplankton community composition with Cladocera and particulate phosphorus (PP). This indicate that the sediment resuspension of shallow lakes has a significant effect on the species richness and diversity of bacterioplankton, whose the main reason is that the community structure of zooplankton and nutrient are influenced by the sediment resuspension. The mechanism of this process may include top-down and bottom-up effect. Thus, we hypothesize that the sediment resuspension has a significant influence on microbial foodweb, heterogeneity in shallow eutrophic lakes.2. Three clone libraries were constructed. In D-SR, D-WR and D-C samples total 26,33 and 31 operational taxonomic units (OTUs) were detected in each clone library respectively.Most of the OTUs belong to phyla of kingdom bacteria:alpha-, beta-, and gamma-Subdivision of Proteobacteria, Actinobacteria, Cyanobacteria, Bacteroidetes, Planctomycetes. In D-SR, and D-C samples Proteobacteria were main edificators, 85% and 87% respectively. a-Proteobacteria is one of the major taxa. Although the D-WR in the Proteobacteria is also dominant but its percentage of only 55%, Actinobacteria, and Bacteroides were have accounted for a large proportion of,24% and 9% respectively. We also found the Planctomycetes this member of bacteria, which we know little about it.3. Nonmetric multidimensional scaling (NMDS) was applied to analyze the similar between the samples from five different treatments. The results demonstrated that the bacterioplankton community composition was diverse in enclosures. The difference of bacterioplankton community was higher in seasonal than spatial. That is, the differences of samples collected at varying time is greater than the treatment enclosures. The bacterioplankton community composition was dominated by members of theγ-Proteobacteria,α-Proteobacteria, Actinobacteria, and Bacteroidetes groups.4. With the result of T-RFLP analysis of bacterioplankton community structure, based on the use of multivariate statistical analysis of bacterioplankton community structure and environmental factors relevant, results showed that TP, Chl a, and TN with the bacterioplankton community structure with a highly significant correlation (P<0.01), SD, and pH also has a significant correlation (P<0.05).