More Like this

1. Prediction of anthropogenic debris and its association with geomorphology in US urban streams

   https://doi.org/10.1016/j.scitotenv.2025.179317  

   Farooq, Nageen; Jefferson, Anne; Greising, Chris; Kearns, Kayla; Muratori, Sophia; Snyder, Kylie (May 2025, Science of The Total Environment)

   Anthropogenic debris in urban streams is a persistent environmental problem, yet previous studies have focused largely on how land use influences debris concentrations, while neglecting the potential role of fluvial geomorphology in mediating storage. To examine relationships between in-stream debris concentrations and different geomorphologic characteristics, catchment characteristics, and catchment and riparian land cover in US urban streams, we collected data on debris (>5 cm), large wood, cross-section and longitudinal profiles, and sediment sizes in 24 stream reaches in two metropolitan areas (Cleveland, Ohio; Charlotte, North Carolina). Debris concentrations ranged from 0.18 to 4.7 pieces/m bankfull width, with an average of 1.55 pieces/m. Plastic comprised 71.8 % of the collected debris, and in two reaches with repeated measurements, debris re-accumulated quickly following removal. In city-specific multiple linear regression models, debris concentrations across stream reaches was explained as well or better by geomorphologic variables than GIS variables, but when data from the two cities were combined, the opposite was true. Cross-section characteristics were among the strongest predictors of debris concentration in both cities. Our analysis suggests that roughness associated with stream banks plays an important role in debris storage, through trapping debris on riparian vegetation and by creating width constrictions that lead to low velocity zones and debris settling on the bed. Future work on interactions between bank and vegetative roughness and anthropogenic debris may reveal generalizable predictors of debris storage in urban streams. 

   more » « less
2. Carbon Emissions From Low‐Order Streams in a Tropical, High‐Elevation, Peatland Ecosystem Are Mediated by Catchment Morphology

   https://doi.org/10.1029/2024WR038036  

   Whitmore, Keridwen_M; DelVecchia, Amanda_G; Farquhar, Elizabeth; Rocher‐Ros, Gerard; Suárez, Esteban; Riveros‐Iregui, Diego_A (April 2025, Water Resources Research)

   Abstract Inland waters emit large amounts of carbon and are key players in the global carbon budget. Particularly high rates of carbon emissions have been reported in streams draining mountains, tropical regions, and peatlands. However, few studies have examined the spatial variability of CO₂concentrations and fluxes occurring within these systems, particularly as a function of catchment morphology. Here we evaluated spatial patterns of CO₂in three tropical, headwater catchments in relation to the river network and stream geomorphology. We measured dissolved carbon dioxide (pCO₂), aquatic CO₂emissions, discharge, and stream depth and width at high spatial resolutions along multiple stream reaches. Confirming previous studies, we found that tropical headwater streams are an important source of CO₂to the atmosphere. More notably, we found marked, predictable spatial organization in aquatic carbon fluxes as a function of landscape position. For example,pCO₂was consistently high (>10,000 ppm) at locations close to groundwater sources and just downstream of hydrologically connected wetlands, but consistently low (<1,000 ppm) in high gradient locations or river segments with larger drainage areas. Taken together, our findings suggest that catchment area and stream slope are important drivers ofpCO₂and gas transfer velocity (k) in mountainous streams, and as such they should be considered in catchment‐scale assessments of CO₂emissions. Furthermore, our work suggests that accurate estimation of CO₂emissions requires understanding of dynamics across the entire stream network, from the smallest seeps to larger streams. 

   more » « less
3. Spatiotemporal variability of gas transfer velocity in a tropical high‐elevation stream using two independent methods

   https://doi.org/10.1002/ecs2.3647  

   Whitmore, Keridwen M.; Stewart, Nehemiah; Encalada, Andrea C.; Suárez, Esteban; Riveros‐Iregui, Diego A. (July 2021, Ecosphere)

   Abstract Streams in high‐elevation tropical ecosystems known as páramos may be significant sources of carbon dioxide (CO₂) to the atmosphere by transforming terrestrial carbon to gaseous CO₂. Studies of these environments are scarce, and estimates of CO₂fluxes are poorly constrained. In this study, we use two independent methods for measuring gas transfer velocity (k), a critical variable in the estimation of CO₂evasion and other biogeochemical processes. The first method, kinematick₆₀₀(k_600‐K), is derived from an empirical relationship between temperature‐adjustedk(k₆₀₀) and the physical characteristics of the stream. The second method, measuredk₆₀₀(k_600‐M), estimates gas transfer velocity in the stream by in situ measurements of dissolved CO₂(pCO₂) and CO₂evasion to the atmosphere, adjusting for temperature. Measurements were collected throughout a 5‐week period during the wet season of a peatland‐stream transition within a páramo ecosystem located above 4000 m in elevation in northeastern Ecuador. We characterized the spatial heterogeneity of the 250‐m reach on five occasions, and both methods showed a wide range of variability ink₆₀₀at small spatial scales. Values ofk_600‐Kranged from 7.42 to 330 m/d (mean = 116 ± 95.1 m/d), whereas values ofk_600‐Mranged from 23.5 to 444 m/d (mean = 121 ± 127 m/d). Temporal variability ink₆₀₀was driven by increases in stream discharge caused by rain events, whereas spatial variability was driven by channel morphology, including stream width and slope. The two methods were in good agreement (less than 16% difference) at high and medium stream discharge (above 7.0 L/s). However, the two methods considerably differed from one another (up to 73% difference) at low stream discharge (below 7.0 L/s, which represents 60% of the observations collected). Our study provides the first estimates ofk₆₀₀values in a high‐elevation tropical catchment across steep environmental gradients and highlights the combined effects of hydrology and stream morphology in co‐regulating gas transfer velocities in páramo streams. 

   more » « less
4. Salty chemical cocktails as water quality signatures: Longitudinal trends and breakpoints along different U.S. streams

   https://doi.org/10.1016/j.scitotenv.2024.172777  

   Shelton, Sydney A; Kaushal, Sujay S; Mayer, Paul M; Shatkay, Ruth R; Rippy, Megan A; Grant, Stanley B; Newcomer-Johnson, Tammy A (June 2024, Science of The Total Environment)

   Along urban streams and rivers, various processes, including road salt application, sewage leaks, and weathering of the built environment, contribute to novel chemical cocktails made up of metals, salts, nutrients, and organic matter. In order to track the impacts of urbanization and management strategies on water quality, we conducted longitudinal stream synoptic (LSS) monitoring in nine watersheds in five major metropolitan areas of the U.S. During each LSS monitoring survey, 10–53 sites were sampled along the flowpath of streams as they flowed along rural to urban gradients. Results demonstrated that major ions derived from salts (Ca2+, Mg2+, Na+, and K+) and correlated elements (e.g. Sr2+, N, Cu) formed ‘salty chemical cocktails’ that increased along rural to urban flowpaths. Salty chemical cocktails explained 46.1% of the overall variability in geochemistry among streams and showed distinct typologies, trends, and transitions along flowpaths through metropolitan regions. Multiple linear regression predicted 62.9% of the variance in the salty chemical cocktails using the six following significant drivers (p < 0.05): percent urban land, wastewater treatment plant discharge, mean annual precipitation, percent silicic residual material, percent volcanic material, and percent carbonate residual material. Mean annual precipitation and percent urban area were the most important in the regression, explaining 29.6% and 13.0% of the variance. Different pollution sources (wastewater, road salt, urban runoff) in streams were tracked downstream based on salty chemical cocktails. Streams flowing through stream-floodplain restoration projects and conservation areas with extensive riparian forest buffers did not show longitudinal increases in salty chemical cocktails, suggesting that there could be attenuation via conservation and restoration. Salinization represents a common urban water quality signature and longitudinal patterns of distinct chemical cocktails and ionic mixtures have the potential to track the sources, fate, and transport of different point and nonpoint pollution sources along streams across different regions. 

   more » « less
5. Linking permafrost to the abundance, biomass, and energy density of fish in Arctic headwater streams

   https://doi.org/10.1002/ecs2.70270  

   Carey, Michael P; Koch, Joshua C; O'Donnell, Jonathan A; Poulin, Brett A; Zimmerman, Christian E (May 2025, Ecosphere)

   Abstract Permafrost thaw alters groundwater flow, river hydrology, stream‐catchment interactions, and the availability of carbon and nutrients in headwater streams. The impact of permafrost on watershed hydrology and biogeochemistry of headwater streams has been demonstrated, but there is little understanding of how permafrost influences fish in these ecosystems. We examined relations among permafrost characteristics, the resulting changes in water temperature, stream hydrology (e.g., discharge flashiness), and macroinvertebrates, with the abundance, biomass, and energy density of juvenile Dolly Varden (Salvelinus malma) and Arctic Grayling (Thymallus arcticus) across 10 headwater streams in northwestern Alaska. Macroinvertebrate density was driven by concentrations of dissolved carbon and nutrients supporting stream food webs. Dolly Varden abundance was primarily related to water temperature with fewer fish in warmer streams, whereas Dolly Varden energy density decreased with the flashiness of the headwater streams. Dolly Varden biomass was related to both temperature and bottom‐up food web effects. The energy density of Arctic Grayling decreased with warmer temperatures and discharge flashiness. These relations demonstrate the importance of terrestrial–aquatic connections in permafrost landscapes and indicate the complexity of landscape effects on fish. Because permafrost thaw is one of the most impactful changes occurring as the Arctic warms, an improved understanding of how stream temperature, hydrology, and bottom‐up food web processes influence fish populations can aid forecasting of future conditions across the Arctic. 

   more » « less