Riparian habitats provide resource subsidies to aquatic ecosystems in the form of allochthonous litter which supply nutrients to aquatic consumers. Throughout the western United States, riparian habitats have been invaded by non-native Russian Olive (Elaeagnus angustifolia) while native riparian species, such as Cottonwood (Populus deltoides), are declining. Russian olive litter is recalcitrant and may be lower quality for aquatic consumers. Therefore, the change in riparian composition from cottonwood to Russian olive has the potential to alter the quantity and quality of allochthonous subsidies in invaded habitats. Our study investigated the influence of Russian olive and the native cottonwood allochthonous litter inputs on aquatic productivity in an experimental stream mesocosm. The specific objectives are to 1) Compare the effects of a non-native (Russian Olive) and a native (Cottonwood) litter on nutrient cycling and ecosystem efficiency. 2) Determine the effect of recalcitrant litter on aquatic invertebrate production in their aquatic and emergent life stages. We hypothesized that experimental units that received Russian olive litter would experience reduced algal and invertebrate production compared to units with cottonwood litter. We simulated isolated pool-riffle during low-flow conditions in 24 experimental stream mesocosms. Treatments consisted of Russian Olive fruits and leaf litter, Cottonwood leaf litter, and a negative control with no litter. Mesocosms were operated for 90 days in which we monitored water chemistry, decomposition rates, and algal and invertebrate production in each experimental unit. Preliminary results indicate changes in algae community and composition as well as changes in aquatic life stages of invertebrates. With these findings we are seeing a shift in the base of the food web which will have cascading effects on the entire ecosystem.