Effects of Pollutants in Urban Wastewater on Rhizoplane Microbial Communities in Constructed Wetlands: Resistance and Resilience of Macrophyte-Associated Microbiomes

The impact of pollutants in urban wastewater on Constructed Wetlands (CWs) rhizoplane microbial communities remains quite understudied. Our study explores how civil wastewater influences the structure and ecological stability of rhizoplane microbial communities associated with three macrophytes: Nerium oleander L., Arundo donax L., and Juncus conglomeratus L. in simulated conditions as in the case of CWs. Therefore, a pot experiment was set up, using wastewater repeated exposure of the three macrophytes, to assess the microbial (bacteria and fungi) resistance and resilience by means of next-generation sequencing. The results showed that all three macrophytes contributed to pollutant removal; however, the effects on microbial communities were taxon-specific. In general, the rhizobacterial community exhibited moderate resilience and low resistance to wastewater, indicating a partial recovery post-disturbance. The fungal community showed high resistance (ResI = 0.99), in contrast with limited resilience (RI < 1), suggesting a stable but less dynamic response to the wastewater exposure. Effluent repeated addition positively influenced the relative abundance of certain bacteria taxonomical groups, specifically Firmicutes and Actinobacteria, but also of some fungal taxa. Our findings underscore the key role of microbial communities in CWs, where complementary resistance and resilience strategies contribute to system stability, plant health, and pollutant attenuation.