Responses of Aquatic Fungal Communities on Leaf Litter to Temperature-Change Events

Increases of extreme weather events are predicted to occur with ongoing climate change, but impacts to freshwaters have rarely been examined. We assessed the effects of temperature on leaf-litter associated fungi by exposing leaves colonized in a stream to 18 degrees C (control), 25 degrees C, or 18 degrees C after freezing. Treatments altered fungal dominance on leaves; Lunulospora curvula sporulation was stimulated by increased temperature and stopped by the freeze-thaw treatment. Fungal biomass and diversity decreased at 18 degrees C after freezing, but not at 25 degrees C. Leaf decomposition was retarded by the freeze-thaw treatment (k = -0.024 day(-1)) and stimulated at 25 degrees C (k = -0.069 day(-1)). Results suggest that occasional freezing may constrain fungal diversity and their ecological functions, while warming appears to accelerate plant-litter decomposition in streams.