Rhizosphere microorganisms are crucial to the DOM transformation and microbiome stability in the constructed wetlands

Constructed wetlands (CWs) play key roles in the water purification and host a range of processes that degrade and modify dissolved organic matter (DOM). Microbes in sediment and rhizosphere environments strongly influence DOM's chemodiversity. To unravel the biotic mechanisms that control the structure and patterns of DOM and microbial communities in CWs, we combined high throughput sequencing and 3DEEM. DOM components extracted by parallel factor analysis were mainly tyrosine-like, protein-like and tryptophan-like substance. Components and 4 optical indices showed seasonal variation in the study periods. Sediment (SE) and rhizosphere (PR) microbial communities differed in dominant phyla. Larger proportions of generalist (5.32% vs. 2.89%) and specialist (1.57% vs. 1.23%) were estimated in PR systems than SE systems. Deterministic processes, especially homogeneous selection events (38.33%) were identified as the dominant microbial community assembly mechanisms in SE systems while stochastic process (58.33%) happens more often in PR system. Network analysis revealed that networks during extreme periods exhibited lower stability but denser modules compared to normal periods. Meanwhile, PR microbes could enhance the stability of SE community and benefit CW performance. DOM components had strong correlations with genera, which were also identified as biomarkers to classified SE and PR via random forest. PR's members have limited related to less DOM components in comparison with SE because of the narrow ecological niche and both two systems show function dependency. Finally, we figured out two pathways to decipher the interaction between DOM and CWs' microorganism, i.e., sediment microbes → DOM and sediment microbes → rhizosphere microbes → DOM. This study provides a new perspective for the construction and management of constructed wetlands. © 2026 Elsevier B.V.