Biodiversity assessment in a floating treatment wetland established in a stormwater pond

Floating treatment wetland (FTW) are a nature-based solution delivering a wide range of ecosystem services when applied in water bodies, such as lakes and rivers. They are recognized for delivering biodiversity, aesthetic integration, and water quality enhancement through phytoremediation processes, although research is still needed to go deeper into the processes underlying the performance of these systems and evaluate the extent of biodiversity promotion especially on pond ecosystems. This study aimed to assess the plant establishment and biodiversity associated with an FTW set up in a rural artificial stormwater pond, with a polyculture comprising Iris germanica, Acorus gramineus, Caltha palustris, and Typha latifolia set in a cork agglomerate platform. For this, it was assessed the culturable bacterial communities associated to the floating platform and the rooting system, and the macroinvertebrates associated to the FTW and to the pond margin. Culturable bacterial communities colonizing the floating platform biofilm and the plant rhizosphere were isolated, identified by 16S rRNA, and characterized for their ability to produce plant growth-promoting substances (e.g., indole-acetic acid, siderophores). There was a high bacterial genera diversity associated with the FTW and with the ability to produce plant growth-promoting substances. Bacterial strains with outstanding growth-promoting traits can be used in the future to support phytoremediation strategies or plant resilience to climate change-related abiotic stresses. Regarding the biodiversity of macrofauna, namely macroinvertebrates, associated with FTW, they were mostly from the order Odonata. The FTW attracted mainly individuals of the genus Coenagrion, which represented more than 80 % of the associated fauna. The full life cycle of dragonflies and damselflies occurred in the FTW. These systems proved to be a hotspot of biodiversity supporting water and landscape management plans, besides aesthetics integration. This study gives new insights into broadening the FTW applications in stormwater or prospects to polluted water.