Vertical-scale spatial influence of radial oxygen loss on rhizosphere microbial community in constructed wetland

Complex interactions between plants and microorganisms form the basis of constructed wetlands (CWs) for pollutant removal. In the rhizosphere, radial oxygen loss (ROL) plays a key role in the activity and abundance of functional microorganisms. However, little has been done to explore how ROL would influence the niche dif-ferentiation of microbial communities at different vertical spatial scales. We demonstrate that ROL decreases with depth, promoting an oxidation-reduction rhizosphere microecosystem in CWs. The high level of ROL in the upper layer could support the oxygen supply for aerobic bacteria (Haliangium), facilitating the COD (60%) and NH4+-N (50%) removal, whereas the enrichment of denitrifiers (e.g., Hydrogenophaga and Ralstonia) and meth-anotrophs (Methanobaterium) in the lower layer could stimulate denitrification. The function prediction results further certified that the abundance of genes catalyzing nitrifying and denitrification processes were significantly enhanced in the upper and bottom layers, respectively, which was attributed to the oxygen concentration gradient in the rhizosphere. This study contributes to further unraveling the rhizosphere effect and enables an improved understanding of the decontamination mechanisms of CWs.

Automated summary

Complex interactions between plants and microorganisms in constructed wetlands (CWs) play a crucial role in pollutant removal. The study examines the impact of radial oxygen loss (ROL) on microbial communities at different vertical spatial scales. It is found that ROL decreases with depth, leading to an oxidation-reduction rhizosphere microecosystem in CWs. The presence of aerobic bacteria in the upper layer and denitrifiers and methanotrophs in the lower layer contributes to COD and NH4+-N removal, as well as denitrification.