Algal growth has been shown to influence carbon breakdown rates in aquatic ecosystems; however, the magnitude and direction of these effects differ based on ecosystem context. To explore algal priming effects on decomposition in anthropogenically-impacted ecosystems, I conducted light manipulation experiments in three streams, each surrounded by different land uses (urban, row crop, and CAFO) across Nebraska. I measured leaf breakdown rates, metabolic activity, fungal and algal biomass, and leaf percent carbon (C) and phosphorus (P) to assess the effect of light differences. Experimental streams were impacted by sedimentation and turbidity over the course of the leaf incubation. Still, I observed significantly higher algal biomass as chlorophyll a in light treatments at two of my three streams. I observed negative relationships between algal biomass and fungal biomass as ergosterol at all my sites but contrasting relationships between algal biomass and respiration rates at my two agricultural sites. Additionally, breakdown rates were not significantly different by light treatment at any of my row crop sites, but they were higher at two of my last three collection dates at the CAFO site. Overall, leaf C:P declined over the course of the experiment. These results support prior studies that light levels can alter breakdown rates of allochthonous material in streams. They shed light on the influence that changing light levels can exert over carbon processing in streams.