Climate change is predicted to increase stream temperatures in the Midwest up to 6°C by 2100, which may alter stream ecosystem function. To explore these impacts, we used replicated recirculating mesocosms (n=24) to examine the effects of warming on biofilm colonization, metabolism, and nutrient removal of ammonium (NH4+-N) and soluble reactive phosphorus (SRP). We established three temperature treatments (20℃, 23℃, and 26℃) and compared epilithic biofilms colonizing cobble substrates to heterotrophic biofilms colonizing sugar maple leaves (Acer saccharum). We measured chlorophyll-a (chla) on cobble, community respiration (CR) on leaves, and nutrient removal rates (k, hr-1) of NH4+-N and SRP weekly for 21 days. We found that warming did not change epilithon chla, nor leaf CR (Generalized linear mixed model; p>0.05). For nutrients, warming increased NH4+-N removal for both leaves and cobble; k for cobble at 20°C was 2.3 hr-1 (Bayesian univariate multilevel model; 75% Credible Interval=1.9, 2.7), and 3.5 hr-1 at 26°C (3.1, 4.0), while k for leaves at 20°C was 0.5 hr-1 (0.4, 0.6), and at 26°C was 1.1 hr-1 (1.0, 1.2). In contrast, warming only altered SRP removal for cobble; k at 20°C was 1.1 hr-1 (0.8, 1.3), and at 26°C was 1.9 hr-1 (1.7, 2.2), but not for leaves (k at 20°C = 0.1 hr-1 (0.1, 0.4), k at 26°C = 0.4 hr-1 (0.2, 0.6)). We show that warming-induced changes in nutrient removal are mediated by substrate, and that NH4+-N removal may be more sensitive to elevated temperatures, with implications for nutrient cycling under a warmer future.