Leaf litter and its associated microorganisms play a key role in phosphorus (P) uptake in streams. However, the response of aquatic hyphomycete fungi, the dominant litter decomposers in forest streams, to elevated concentrations of dissolved P remains unclear. Whole-stream nutrient addition experiments at Coweeta Hydrologic Laboratory suggest that as the litter P content increases, fungal biomass also increases but at a slower rate, potentially indicating ‘luxury’ storage of P. To investigate this, we conducted short-term P-enrichment experiments to assess how dissolved P concentrations in the water column influence the biomass and P content of litter-associated fungi. Leaf litter of two species, fast-decomposing tulip poplar (Liriodendron tulipifera) and slow-decomposing white oak (Quercus alba), was incubated in a second-order stream and underwent short-term P enrichment at three stages of the decay process: early (day 50), middle (day 100), and late decay (day 150). Phosphorus additions were conducted at each decomposition stage by enriching stream water P concentration to 200 ug/L for one-week. During each P addition, litter samples were collected after 0, 4, 8, 24, 72, and 168 hours after P enrichment started. Litter samples were analyzed for P content, fungal biomass (measured as ergosterol), and phosphatase activity. Fungal biomass did not increase proportionally with increased litter P content, suggesting either luxury storage of P or shifts in fungal community composition toward more P-rich taxa. To further explore this, nuclear magnetic resonance (NMR) is being used to identify P-containing compounds, particularly polyphosphate, the primary storage form of P in fungi. Additionally, ITS sequencing will detect potential shifts in community structure during each P addition.