| The activity of ammonia-oxidizing bacteria (AOB) in different layers of Integrated vertical-flow constructed wetlands (IVCW) treating eutrophic scenic water was measured, and the diversity and spatial distribution of AOB community structure in IVCW was investigated using PCR-DGGE. The results indicated that because of the integrated influence of competition of plant rhizodeposition, heterotrophic bacteria, DO and ammonia concentration, there were significant spatial differences in the activity and diversity of AOB along the flow direction of wetland. The activity of AOB was 0.79 mg·(kg·h)-1 (in NO-3-N, the same below) near the surface of down-flow system in IVCW. From the surface of down-flow system to up-flow system, the activity of AOB decreased gradually, and slightly increased to 0.17 mg·(kg·h)-1 near the surface of up-flow system. The spatial variation of diversity of AOB showed the similar change trend with the activity in IVCW and the diversity index in down-flow system (1.92) were higher than those in up-flow system (1.65). Most of AOB belong to oligotrophic bacterium in IVCW, and the population of ammonia-oxidizing bacteria showed a higher percentage of Nitrosomonas-like sequences from the wetland samples. Uncultured beta proteobacterium, Comamonas sp., Nitrosomonas oligotropha were also detected. The variation of the AOB community demonstrated spatial pattern in IVCW, which might be related to different wetland environment. |
