Browsing by Author "Marti, Eugenia"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Co-located contemporaneous mapping of morphological, hydrological, chemical, and biological conditions in a 5th-order mountain stream network, Oregon, USA
    Ward, Adam S.; Zarnetske, Jay P.; Baranov, Viktor; Blaen, Phillip J.; Brekenfeld, Nicolai; Chu, Rosalie; Derelle, Romain; Drummond, Jennifer D.; Fleckenstein, Jan H.; Garayburu-Caruso, Vanessa; Graham, Emily B.; Hannah, David; Harman, Ciaran J.; Herzog, Skuyler; Hixson, Jase; Knapp, Julia L. A.; Krause, Stefan; Kurz, Marie J.; Lewandowski, Joerg; Li, Angang; Marti, Eugenia; Miller, Melinda C.; Milner, Alexander M.; Neil, Kerry; Orsini, Luisa; Packman, Aaron I.; Plont, Stephen; Renteria, Lupita; Roche, Kevin; Royer, Todd; Schmadel, Noah M.; Segura, Catalina; Stegen, James; Toyoda, Jason; Wells, Jacqueline; Wisnoski, Nathan I.; Wondzell, Steven M. (2019-10-22)
    A comprehensive set of measurements and calculated metrics describing physical, chemical, and biological conditions in the river corridor is presented. These data were collected in a catchment-wide, synoptic campaign in the H. J. Andrews Experimental Forest (Cascade Mountains, Oregon, USA) in summer 2016 during low-discharge conditions. Extensive characterization of 62 sites including surface water, hyporheic water, and streambed sediment was conducted spanning 1st- through 5th-order reaches in the river network. The objective of the sample design and data acquisition was to generate a novel data set to support scaling of river corridor processes across varying flows and morphologic forms present in a river network. The data are available at https://doi.org/10.4211/hs.f4484e0703f743c696c2e1f209abb842 (Ward, 2019).
  • Thumbnail Image
    Drivers of nitrogen transfer in stream food webs across continents
    Norman, Beth C.; Whiles, Matt R.; Collins, Sarah M.; Flecker, Alexander S.; Hamilton, Steve K.; Johnson, Sherri L.; Rosi, Emma J.; Ashkenas, Linda R.; Bowden, William B.; Crenshaw, Chelsea L.; Crowl, Todd; Dodds, Walter K.; Hall, Robert O.; El-Sabaawi, Rana; Griffiths, Natalie A.; Marti, Eugenia; McDowell, William H.; Peterson, Scot D.; Rantala, Heidi M.; Riis, Tenna; Simon, Kevin S.; Tank, Jennifer L.; Thomas, Steven A.; von Schiller, Daniel; Webster, Jackson R. (2017-12)
    Studies of trophic-level material and energy transfers are central to ecology. The use of isotopic tracers has now made it possible to measure trophic transfer efficiencies of important nutrients and to better understand how these materials move through food webs. We analyzed data from thirteen N-15-ammonium tracer addition experiments to quantify N transfer from basal resources to animals in headwater streams with varying physical, chemical, and biological features. N transfer efficiencies from primary uptake compartments (PUCs; heterotrophic microorganisms and primary producers) to primary consumers was lower (mean 11.5%, range <1% to 43%) than N transfer efficiencies from primary consumers to predators (mean 80%, range 5% to >100%). Total N transferred (as a rate) was greater in streams with open compared to closed canopies and overall N transfer efficiency generally followed a similar pattern, although was not statistically significant. We used principal component analysis to condense a suite of site characteristics into two environmental components. Total N uptake rates among trophic levels were best predicted by the component that was correlated with latitude, DIN:SRP, GPP:ER, and percent canopy cover. N transfer efficiency did not respond consistently to environmental variables. Our results suggest that canopy cover influences N movement through stream food webs because light availability and primary production facilitate N transfer to higher trophic levels.
  • Thumbnail Image
    Solute Transport and Transformation in an Intermittent, Headwater Mountain Stream with Diurnal Discharge Fluctuations
    Ward, Adam S.; Kurz, Marie J.; Schmadel, Noah M.; Knapp, Julia L. A.; Blaen, Phillip J.; Harman, Ciaran J.; Drummond, Jennifer D.; Hannah, David M.; Krause, Stefan; Li, Angang; Marti, Eugenia; Milner, Alexander M.; Miller, Melinda C.; Neil, Kerry; Plont, Stephen; Packman, Aaron I.; Wisnoski, Nathan I.; Wondzell, Steven M.; Zarnetske, Jay P. (MDPI, 2019-10-23)
    Time-variable discharge is known to control both transport and transformation of solutes in the river corridor. Still, few studies consider the interactions of transport and transformation together. Here, we consider how diurnal discharge fluctuations in an intermittent, headwater stream control reach-scale solute transport and transformation as measured with conservative and reactive tracers during a period of no precipitation. One common conceptual model is that extended contact times with hyporheic zones during low discharge conditions allows for increased transformation of reactive solutes. Instead, we found tracer timescales within the reach were related to discharge, described by a single discharge-variable StorAge Selection function. We found that Resazurin to Resorufin (Raz-to-Rru) transformation is static in time, and apparent differences in reactive tracer were due to interactions with different ages of storage, not with time-variable reactivity. Overall we found reactivity was highest in youngest storage locations, with minimal Raz-to-Rru conversion in waters older than about 20 h of storage in our study reach. Therefore, not all storage in the study reach has the same potential biogeochemical function and increasing residence time of solute storage does not necessarily increase reaction potential of that solute, contrary to prevailing expectations.
  • Thumbnail Image
    Spatial and temporal variation in river corridor exchange across a 5th-order mountain stream network
    Ward, Adam S.; Wondzell, Steven M.; Schmadel, Noah M.; Herzog, Skuyler; Zarnetske, Jay P.; Baranov, Viktor; Blaen, Phillip J.; Brekenfeld, Nicolai; Chu, Rosalie; Derelle, Romain; Drummond, Jennifer D.; Fleckenstein, Jan H.; Garayburu-Caruso, Vanessa; Graham, Emily B.; Hannah, David; Harman, Ciaran J.; Hixson, Jase; Knapp, Julia L. A.; Krause, Stefan; Kurz, Marie J.; Lewandowski, Joerg; Li, Angang; Marti, Eugenia; Miller, Melinda C.; Milner, Alexander M.; Neil, Kerry; Orsini, Luisa; Packman, Aaron I.; Plont, Stephen; Renteria, Lupita; Roche, Kevin; Royer, Todd; Segura, Catalina; Stegen, James; Toyoda, Jason; Wells, Jacqueline; Wisnoski, Nathan I. (2019-12-20)
    Although most field and modeling studies of river corridor exchange have been conducted at scales ranging from tens to hundreds of meters, results of these studies are used to predict their ecological and hydrological influences at the scale of river networks. Further complicating prediction, exchanges are expected to vary with hydrologic forcing and the local geomorphic setting. While we desire predictive power, we lack a complete spatiotemporal relationship relating discharge to the variation in geologic setting and hydrologic forcing that is expected across a river basin. Indeed, the conceptual model of Wondzell (2011) predicts systematic variation in river corridor exchange as a function of (1) variation in baseflow over time at a fixed location, (2) variation in discharge with location in the river network, and (3) local geomorphic setting. To test this conceptual model we conducted more than 60 solute tracer studies including a synoptic campaign in the 5th-order river network of the H. J. Andrews Experimental Forest (Oregon, USA) and replicate-intime experiments in four watersheds. We interpret the data using a series of metrics describing river corridor exchange and solute transport, testing for consistent direction and magnitude of relationships relating these metrics to discharge and local geomorphic setting. We confirmed systematic decrease in river corridor exchange space through the river networks, from headwaters to the larger main stem. However, we did not find systematic variation with changes in discharge through time or with local geomorphic setting. While interpretation of our results is complicated by problems with the analytical methods, the results are sufficiently robust for us to conclude that space-for-time and time-for-space substitutions are not appropriate in our study system. Finally, we suggest two strategies that will improve the interpretability of tracer test results and help the hyporheic community develop robust datasets that will enable comparisons across multiple sites and/or discharge conditions.
  • Thumbnail Image
    Twenty-six key research questions in urban stream ecology: an assessment of the state of the science
    Wenger, Seth J.; Roy, Allison H.; Jackson, C. Rhett; Bernhardt, Emily S.; Carter, Timothy L.; Filoso, Solange; Gibson, Catherine A.; Hession, W. Cully; Kaushal, Sujay S.; Marti, Eugenia; Meyer, Judy L.; Palmer, Margaret A.; Paul, Michael J.; Purcell, Alison H.; Ramirez, Alonso; Rosemond, Amy D.; Schofield, Kate A.; Sudduth, Elizabeth B.; Walsh, Christopher J. (The North American Benthological Society, 2009-10-27)
    Urban streams have been the focus of much research in recent years, but many questions about the mechanisms driving the urban stream syndrome remain unanswered. Identification of key research questions is an important step toward effective, efficient management of urban streams to meet societal goals. We developed a list of priority research questions by: 1) soliciting input from interested scientists via a listserv and online survey, 2) holding an open discussion on the questions at the Second Symposium on Urbanization and Stream Ecology, and 3) reviewing the literature in the preparation of this paper. We present the resulting list of 26 questions in the context of a review and summary of the present understanding of urban effects on streams. The key questions address major gaps in our understanding of ecosystem structure and function responses (e.g., what are the sublethal impacts of urbanization on biota?), characteristics of urban stream stressors (e.g., can we identify clusters of covarying stressors?), and management strategies (e.g., what are appropriate indicators of ecosystem structure and function to use as management targets?). The identified research needs highlight our limited understanding of mechanisms driving the urban stream syndrome and the variability in characteristics of the effects of urbanization across different biogeoclimatic conditions, stages of development, government policies, and cultural norms. We discuss how to proceed with appropriate management activities given our current incomplete understanding of the urban stream syndrome.