Effects of plant and influent C:N:P ratio on microbial diversity in pilot-scale constructed wetlands

Microbial processes within the rhizosphere of constructed wetlands are crucial to wastewater treatment, but the relation between microbial community diversity in rhizosphere, plant growth and water quality are unclear at present. The effects of plant growth, water C:N:P ratio and their interaction on microbial diversity in the rhizosphere were studied in synthetic wastewater in planted and unplanted wetlands during three different seasons. The physiological profile of microbial community-level in each wetland was assessed using substrate utilization patterns gathered via BIOLOG™ ECO plates. Plant had a significant effect on AWCD parameter, since the planted wetlands usually had a higher the total microbial activity than the unplanted over the study period. The Shannon, Simpson and McIntosh indices in the planted wetlands were apparently higher than those in the unplanted wetlands under any C:N:P ratio influent condition especially in summer. It was also shown that the unplanted wetlands have a greater shift of the interstitial microbial community than the planted at different seasons, since plant rhizospheres produce a more ecologically stable system in order to resist against shifts in microbial community composition in response to C:N:P ratio change in wastewater. Principal component analysis and clustering analysis indicated that influent C:N:P ratio would induce similar microbial species in the planted wetlands and detach them from the unplanted wetlands.