Short communicationArbuscular mycorrhizal fungi in Australian stormwater biofilters

- Mycorrhizae were found on plant roots of four species growing in stormwater biofilters in three Australian cities.
- Mean annual rainfall and biofilter age had no significant effects on mycorrhizal colonization.
- Presence of mycorrhizae on some biofilter plant roots suggests filter media conditions can support this plant-fungal relationship.

Stormwater biofilters are important tools for managing runoff in urban watersheds. To the authors' knowledge, there have been no accounts examining the presence of mycorrhizal fungi in biofilters. This plant-fungi relationship is an important interaction in most terrestrial ecosystems, playing a role in nutrient dynamics, water cycling, and soil organic matter decomposition. The presence of mycorrhiza in biofilters could have implications for nutrient and metal uptake in plants, and thus enhance removal of target pollutants. Additionally, the establishment, growth, and survivability of plants could be enhanced when roots are colonized by mycorrhizae. The aim of this study was to determine the extent of colonization by arbuscular mycorrhizal fungi in biofilters of varying ages in three Australian cities: Melbourne, Perth, and Sydney. The 32 biofilters surveyed supported 56 plant species, with dominant species belonging to the Cyperaceae, Iridaceae, Juncaceae, Onagraceae, Poaceae, and Xanthorrhoeaceae families. Mycorrhizal associations were identified from 4 of the 11 most dominant plant species from 9 different biofilters, but relatively low percentages of mycorrhizal colonization (3-25% colonization) were observed in biofilter plant roots. Mycorrhizal colonization was not related to biofilter age. These results demonstrate that mycorrhizal fungi colonize plant roots growing in biofilters. These findings provide useful evidence of the presence of mycorrhizal fungi in stormwater biofilters that support subsequent investigation into their roles in these systems.