Dissipation characteristics of pyrene and ecological contribution of submerged macrophytes and their biofilms-leaves in constructed wetland

•A non-negligible ecological contribution of submerged macrophytes was observed.•Pyrene dissipation in planted sediments (33–43%) > unplanted system (23–27%).•Biofilms were affected: attached surface > incubation time > pyrene concentration.•PAH-degrading bacteria were positively correlated with the dissipation of pyrene. The dissipation characteristics of pyrene and ecological contribution of submerged macrophytes (Vallisneria natans, Hydrilla verticillata and artificial plant) and their biofilms-leaves in constructed wetland system were investigated by high-throughput sequencing. Results showed a non-negligible ecological contribution of submerged macrophytes and their biofilms-leaves in dissipating pyrene in planted sediments (33.25–43.00%) in contrast with unplanted system (23.25–26.50%). Alpha and Beta diversity analysis indicated that bacterial community structures were influenced in order of attached surface > incubation time > spiking concentration of pyrene in sediment. Difference analysis suggested that attached surface tended to affect the rare genera up to significant level compared with incubation time. In addition, RDA analysis showed that PAH-degrading bacteria in biofilms-leaves of submerged macrophytes were positively correlated with the dissipation ratios of pyrene. Interestingly, nitrogen transforming microorganisms were also influenced in the presence of pyrene, while submerged macrophytes contributed to alleviate the impact.