Profiling and metabolic analysis of microorganisms in bioretention cells vegetated with vetiver and cattail species treating nitrogen and phosphorous

Bioretention cells (BRCs) are increasingly used to treat nutrients in stormwater runoff, with plants known to enhance nitrogen (TN) and phosphorus (TP) uptake. This study investigated the role of rhizosphere microbial communities in TN, TP, and COD removal across three BRCs: an unvegetated control (CP), one vegetated with vetiver (P1), and another with cattail (P2). Detailed microbiome profiling revealed key taxa across phylum, family, and genus levels contributing to nutrient cycling, with P2 showing the highest species richness and diversity based on OTU counts and diversity indices. Proteobacteria, Acidobacteria, and Verrucomicrobiota were the most prominent phyla, aligning with their known roles in nutrient uptake. Key functional taxa included denitrifiers (e.g., Ramlibacter, TRA3-20), Ammonia Oxidizing Bacteria (AOBs) (e.g., MND1, Ellin 6067), and Phosphate Accumulating Organisms (PAOs) (e.g., Comamonadaceae, Vicinamibacteria), supporting TN (>79%) and TP (>84%) removal rates. Distinct microbial compositions between vegetated BRCs confirmed the role of root exudates in microbial selection and enhanced nutrient removal. These findings emphasize the importance of plant-specific rhizosphere effects and microbial selection in optimizing BRC design for stormwater treatment applications.