Influence of Plant Species and De‐Icing Salt on Microbial Communities in Bioretention

Bioretention (BR) systems are green infrastructures used to manage runoff even in cold climates. Bacteria and fungi play a role in BR's performance. This mesocosm study investigated the influence of plant species and de‐icing salt on the diversity, the community composition, and the differential abundance of bacteria and fungi in BR. Cornus sericea, Juncus effusus , Iris versicolor and Sesleria autumnalis were selected. They are planted in BR while differing in terms of biological forms and functional traits. The semi‐synthetic stormwater used was supplemented in spring with four NaCl concentrations (0, 250, 1000 or 4000 mg Cl.L −1 ). Soil was sampled before the experiment, before salt application, and 5 months after the end of the salt treatment. The bacterial and fungal taxa were characterised by sequencing the 16S and ITS regions. The bacteria and fungi found in the BR were adapted to a cold, humid, and contaminated environment. No differences in microbial communities and their functions between treatments were perceivable 5 months after salt treatment. The taxa abundantly present are involved in functions related to the nitrogen cycle, degradation of hydrocarbons, metals tolerance, and remediation. Some were putative plant beneficial symbionts. The presence of certain microbial taxa varied significantly between plant species.