From treetops to river bottoms: Exploring the role of phyllosphere fungi in aquatic fungal communities.

Fungi play a crucial role in aquatic leaf litter decomposition. Aquatic fungi have long been thought to spend the majority of their lives in the water. Here, we explore the possibility of an amphibious life cycle, where phyllosphere fungi spend part of their life cycle in aquatic systems. We used internal transcribed spacer (ITS) fungal sequencing to follow phyllosphere fungi onto submerged litter, and quantitative stable isotope probing (qSIP) to differentiate active and inactive fungi. We found that around 30% of fungi active on aquatic litter entered the stream with the leaf and that these phyllosphere fungi were as active, if not more active than, as the fungi colonizing from the water column. These results demonstrate that phyllosphere fungi are an important part of aquatic fungal communities.