| Black-odorous rivers are the typical and representative consequence of environmental pollution and ecological destruction. Microorganisms in river sediments play an extremely important role in the overlying water-sediment matter cycling process. Aeration is an effective way in the treatment of black-odorous rivers, while different aeration conditions may have different treating effects, which may cause changes of the microbial community structure accordingly. This paper studied the structure of microbial community from urban black-odorous river sediments under five different aeration conditions using two different molecular-biology techniques: PCR-DGGE and16S rDNA clone libraries. Using RDA (redundancy analysis), this paper discussed the relationship between physic-chemical factors and microbial community structures. Results of this study were beneficial to optimize aeration operation conditions, which could provide basis for treatment of urban black-odor river. The results showed as below:(1) Bacterial community structure in urban black-odorous river sediments has a high diversity, which mainly consist of Proteobacteria (including γ-, β-,δ-, ε-and a-subphylum), Firmicutes, Chloroflexi, Verrucomicrobia, Actinobacteria, Acidobacteria, Chlamydiae, Cyanobacteria, Nitrospirae, Nitrospinae, Ignvibacteria, Thermodesulfobacteria, Elusimicrobia, Gemmatimondetes, Lentisphaerae, Bacteroidetes, NC10, and some other unclassified bacteria. Compared with bacterial community structure, archaeal community structure in urban black-odorous river sediments lacks diversity, which mainly consist of Euryarchaeota, Thaumarchaeota, Crenarchaeote and some other unclassified archaea. In the sediment samples, Chlamydiae, Aeromonas, Clostridium, Streptococcus, and Pseudomonas genera containing pathogenic bacteria were detected.(2) In different samples, the dominant bacterial phyla are different and different aeration intensity have different affects on bacterial community structure of urban black-odorous river sediments. In this paper, we introduce different flow velocity of overlying water to characterize different aeration intensity. When the flow velocity are0and0.247m/s, the corresponding dissolved oxygen(DO) are2.14and6.18mg/L, Reynolds number(Re) are0and1311, respectively, Proteobacteria and Firmicutes are the dominant bacterial phyla at the beginning and the end of aeration. When the flow velocity is0.288m/s, the corresponding DO is7.35mg/L, Re is1810, respectively, the dominant bacterial phyla at the beginning and the end of aeration are significantly different, which are Proteobacteria, Firmicutes and Proteobacteria respectively. When the flow velocity are0.320and0.372m/s, the corresponding DO are8.00and8.03mg/L, Re are2133and1736, respectively, Proteobacteria are the dominant bacterial phyla at the beginning and the end of aeration.(3) In different samples, the dominant archaeal phyla are slightly different and different aeration intensity have different impacts on archaeal community structure of urban black-odorous river sediments. When the flow velocity is0, the corresponding DO is2.14mg/L, Re is0, respectively, Methanosarcinales and Methanomicrobiales are the dominant archaeal phyla at the beginning and the end of aeration. When the flow velocity is0.247m/s, the corresponding DO is6.18mg/L, Re is1311, respectively, Methanosarcinales and Thaumarchaeota are the dominant archaeal phyla at the beginning and the end of aeration. When the flow velocity are0.288and0.320m/s, the corresponding DO are7.35and8.00mg/L, Re are1810and2133, respectively, Methanosarcinales and Methanomicrobiales are the dominant archaeal phyla at the beginning and the end of aeration. When the flow velocity is0.372m/s, the corresponding DO is8.03mg/L, Re is1736, respectively, Methanosarcinales are the only dominant archaeal phyla at the beginning of aeration, while Methanosarcinales and Methanomicrobiales are the dominant archaeal phyla at the end of aeration. Generally speaking, in urban black-odorous river sediments, aeration has a greater impact on bacterial community structure than archaeal community structure.(4) Different aeration intensity have a great and different impact on the role of bacterial populations in the progress of material cycling. When the flow velocity is0, the corresponding DO is2.14mg/L, Re is0, respectively, the bacterial populations that are participate in denitrifying and breaking of organic matter has increased at the end of operation. When the flow velocity is0.247m/s, the corresponding DO is6.18mg/L, Re is1311, respectively, the sulfate-reduction bacteria has increased after aeration. When the flow velocity is0.288m/s, the corresponding DO is7.35mg/L, Re is1810, respectively, both the sulfur-oxidizing bacteria and the sulfate-reduction bacteria has increased after aeration, and it may have also promoted the growth of bacterial populations that participate in iron cycle during this operation. When the flow velocity is0.320m/s, the corresponding DO is8.00mg/L, Re is2133, respectively, it mainly promoted the growth of bacteria involved in the degradation of hydrocarbons during this operation. When the flow velocity is0.372m/s, the corresponding DO is8.03mg/L, Re is1736, respectively, both the sulfur-oxidizing bacteria and the sulfate-reduction bacteria has increased after aeration, and it may has also promoted the growth of nitrifying bacterial populations during this operation. But the influence of aeration on the role of archaeal populations that participate in the progress of material cycle were much smaller. It contains a large number of methanogenic archaea and some ammonia-oxidizing archaea in different samples.(5) The ammonia-oxidizing archaea detected have a larger population and have a widely distribution than ammonia-oxidizing bacteria. So, ammonia-oxidizing archaea are preliminarily decided as the dominant group of ammonia-oxidizing microorganisms in the urban black-odorous river sediments.(6) Using RDA (redundancy analysis) in the analysis of the relationship between physic-chemical factors (including T、DO、Re、NH4+-N、TN of overlying water and NH4+-N、TN of pore water) and microbial community structures, and the results showed that DO is a significant factor to both bacterial and archaeal dominant community succession. However, DO, NH4+-N, TN of overlying water have a great impact on the distribution of different bacterial phyla, while none of the physic-chemical factors makes a great difference on the distribution of different archaeal phyla. |
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