Intermittent rivers and ephemeral streams (IRES) comprise more than 50% of global river networks. Despite their prevalence, IRES remain understudied, particularly with respect to effects of periodic flow cessation and dry conditions on aquatic-terrestrial food web linkages. While theoretical models of large perennial rivers emphasize the importance of terrestrial subsidies to aquatic consumers, comparable frameworks are rarely applied to IRES, in which hydrologic variability may result in dynamic cross-directional subsidies.
We assess the relative importance of aquatic and terrestrial resources in IRES using stable isotope analysis of carbon, nitrogen, and hydrogen. Focusing on five drought-prone streams in north Texas that span a gradient of flow intermittency, we test the hypothesis that aquatic resources are important subsidies for terrestrial consumers during periods of drying, while reliance on terrestrial inputs increases during early rewetting phases when in-stream production is reduced. Aquatic and terrestrial basal resources (C₃ and C₄ plants, periphyton, and macrophytes) and consumers (benthic macroinvertebrates, fish, and terrestrial invertebrates) were sampled across multiple seasons. Isotopic mixing models estimate the proportional contribution of aquatic and terrestrial sources to consumer diets, and mixed-effects models evaluate how water availability and quality mediate these subsidy pathways. By testing how aquatic-terrestrial linkages vary across hydrologic regimes, this study aims to clarify the role of dynamic flow intermittency in structuring the food webs of drought-prone stream systems.