River corridor biogeochemical processes and dissolved organic matter (DOM) composition are susceptible to changes in flow regimes and variable inundation conditions. With over 60% of global rivers experiencing at least one dry day per year, and intermittent rivers increasing in the United States, it is critical to understand the effects of drying on key biogeochemical processes like sediment respiration and DOM composition across diverse river ecosystems. Here, we apply DOM thermodynamic theory to investigate the effects of drying and rewetting on sediment DOM chemistry and respiration rates across 33 sites in the contiguous United States. Through laboratory manipulative experiments, we subjected sediments from each site to two treatments over 21 days: a wet treatment with continuously inundated sediments and a dry treatment where sediment allowed to dry. Following treatment, all samples were fully saturated with native river water after which we measured aerobic respiration rates using optodes and conducted subsequent DOM analysis. Overall distributions of DOM properties didn’t vary significantly across treatments, yet treatment effects varied widely within sites. We focused on unique molecular formulas within each site and treatment to better understand moisture effects on DOM thermodynamics and its relationship with respiration rates. Our results further show that moisture conditions modify how DOM thermodynamic favorability is linked to aerobic respiration rates. Specifically, hot spots in respiration rates corresponded with more favorable DOM under wet conditions, while intermediate moisture and dryer conditions spanned a range of DOM favorabilities and respiration rates. These results highlight the importance of understanding moisture-dependent DOM-respiration relationships for generating mechanistic inferences regarding the effects of stream intermittency on global biogeochemical cycles.