Spatial-temporal variation of root-associated aerobic bacterial communities of phragmites australis and the linkage of water quality factors in constructed wetland

Reclaimed water as supplemental source of urban rivers and lakes is regarded as an important approach to improve urban aquatic ecological environment. However, high concentration of nitrogen and phosphorus from reclaimed water can easily lead to eutrophication. Bacteria in constructed wetland are known to play an important role in aquatic ecological remediation. The community structure and diversity of cultural associated bacteria in roots of reed (phragmites australis) growing in reclaimed water management system (reclaimed water treatment unit, cycling water treatment unit, oxidation ponds) in Beijing Olympic Park was investigated in summer and autumn by 16S rDNA cloning, Amplified Ribosomal DNA Restriction Analysis (ARDRA), and sequence homology comparison. Canonical Correspondence Analysis (CCA) and Two way Indicator Species Analysis (TWINSPAN) were used to estimate and statistical test the effects of environmental variables and other explanatory variables on bio-communities, especially to unravel the simultaneous response of the species in a bacteria community to environmental variations when the effects are hidden by other large sources of variation. Cluster analysis on bacteria clones showed that 29 operational taxonomic units (OTUs) were identified based on the similarity of ARDRA banding profiles in 328 cultural clones. Environmental changes resulted into a seasonal shift of bacteria community on community density and diversity in reclaimed water management system. Community density and evenness of root-associated aerobic bacteria in summer increased 76.37%-96.70% than those in autumn. Kinds of inflow (reclaimed water or cycling water) and types of matrix both contributed to spatial variability of bacterial community. There was relative high community diversity and density with reclaimed water inflow and IVCW matrix in reclaimed water treatment unit. Spatial variability of bacteria community in summer increased with altering dominant species in each unit and more accidental species. Therefore, reclaimed water treatment unit in summer with the highest community density (29.9 x 10 super(7)CFU/g roots weight) and the Shannon-Weaver (H'= 1.824). CCA and TWINSPAN analysis revealed that OTU1 and OTU2s in constructed wetland system were with the wide ecological amplitude, which contributed to the stability of constructed wetland system and hardly disturbed by water viabilities, played an important role in material metabolism and energy metabolism. NH sub