Anthropogenic changes to the environment impact aquatic ecosystems by modifying the resource availability, which could influence community composition and function. Organisms that indicate change in the environment are valuable because they shed light on humans’ impact on the ecosystem. Diatoms are useful bioindicators of water quality as they respond to environmental conditions like nutrient inputs.To test the effect of nutrient availability on diatom community composition, we deployed nutrient diffusing substrate at four stream sites before and after nutrient rich tributaries. We expect the phosphorus treatments to select for fast growing taxa, and for the magnitude of this effect to be less at sites with higher background nutrient concentrations. Results from this experiment will provide insight into how stream communities respond to anthropogenic influences.