Changing hydroclimatic conditions in mountain regions are associated with increased variability in streamflow and complicate future predictions of nutrient export and ecosystem responses. Mountain streams are generally heterotrophic, due to the closely linked inputs form the surrounding landscape. We expect that variability in mountain precipitation could alter the synchrony of hydrologic processes (wet deposition and snowmelt) and biological processes (nutrient uptake, assimilation, and fixation) that control carbon and nitrogen availability and demand. Here we investigated how seasonal change in stream metabolism and nitrogen cycling co-varied within two mountain streams draining contrasting catchments in regards to total precipitation accumulation in the Lake Tahoe basin (California and Nevada, USA). Flow regimes varied considerably during the study period across two dry (2021 and 2022), one very wet (2023), and one average water year (2024). Across all years, net ecosystem productivity, and epilithic biomass were positively associated with ammonium concentrations at both streams. Ammonium concentrations were lower in wet years, 33% lower at the larger stream from (15.2 to 10.1 µg L-1) and 42% lower at the smaller stream (from 24.8 to 14.3 µg L-1). Gross primary productivity (GPP) and ecosystem respiration (ER) fluxes were higher during dry years at the larger stream (GPP: 80% higher; 2.3 relative to 0.4 g O2 m-2 d-1 and ER: 23% lower -11.6 relative to 8.2 g O2 m-2 d-1). GPP was generally negligible in the smaller stream ranging from (0.01 to 0.03 g O2 m-2 d-1 from dry to wet years), while ER increased 60% (from -4.1 to -10.2 g O2 m-2 d-1) from dry to wet years. These results suggest even within basins, the responses of streams to changing hydroclimatic conditions and subsequent nutrient availability differ with stream size, where larger streams with sufficient light exposure could experience increased GPP under low flow conditions.