Flow and temperature are strongly linked environmental factors driving ecosystem processes in streams. Stream temperature maxima (T [subscript max_w]) and stream flow minima (Q[subscript min]) can create periods of stress for aquatic organisms. In mountainous areas, such as western North America, recent shifts toward an earlier spring peak flow and...
We propose the experimental use of resazurin (Raz) and develop a metabolically active transient storage (MATS) model to include processes that may provide additional information on transient storage from a biogeochemical perspective in stream ecosystems. Raz is a phenoxazine compound that reduces irreversibly to resorufin (Rru) in the presence of...
We used an in situ steady state ¹⁵N-labeled nitrate (¹⁵NO₃⁻) and acetate (AcO⁻) well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as AcO⁻ influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream. The experimental wells receiving conservative (Cl⁻ and Br)...
Headwater streams comprise nearly 90% of the total length of perennial channels in global catchments. They mineralize organic carbon entering from terrestrial systems, evade terrestrial carbon dioxide (CO₂ ), and generate and remove carbon through in-stream primary production and respiration. Despite their importance, headwater streams are often neglected in global...
Surface and subsurface flow dynamics govern residence time or water age until discharge, which is a key metric of storage and water availability for human use and ecosystem function. Although observations in small catchments have shown a fractal distribution of ages, residence times are difficult to directly quantify or measure...
Groundwater–surface-water (GW-SW) interactions in streams are difficult to quantify because of heterogeneity in hydraulic and reactive processes across a range of spatial and temporal scales. The challenge of quantifying these interactions has led to the development of several techniques, from centimeter-scale probes to whole-system tracers, including chemical, thermal, and electrical...
Excess NO₃⁻ in streams is a growing and persistent problem for both inland and coastal ecosystems, and denitrification is the primary removal process for NO₃⁻. Hyporheic zones can have high denitrification potentials, but their role in reach- and network-scale NO₃⁻ removal is unknown because it is difficult to estimate. We...
In a set of streamside mesocosms, stream ecosystem respiration (ER) increased with biofilm biomass and flow heterogeneity (turbulence) generated by impermeable bed forms, even though those bed forms had no hyporheic exchange. Two streamside flumes with gravel beds (single layer of gravel) were operated in parallel. The first flume had...
In field studies of solute transport, transient storage within lateral cavities and other stream features generates
breakthrough curves (BTCs) with pronounced and persistent skewness. Current solute transport
theory requires that the coefficient of skewness (CSK) decrease over time because the system eventually
reaches Fickian conditions. However, published data show that...
Stream functioning includes simultaneous interaction among solute transport, nutrient processing, and metabolism. Metabolism is measured with methods that have limited spatial representativeness and are highly uncertain. These problems restrict development of methods for up-scaling biological processes that mediate nutrient processing. We used the resazurin–resorufin (Raz-Rru) tracer system to estimate metabolism...