Generality of Hydrologic Transport Limitation of Watershed Organic Carbon Flux Across Ecoregions of the United States

Zarnetske, Jay P.; Bouda, Martin; Abbott, Benjamin W.; Saiers, James E.; Raymond, Peter A.

doi:10.1029/2018gl080005

Cited by 165 publications

(214 citation statements)

References 85 publications

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“…This vertical stratification depends on lithology, the depth and characteristics of fractured rocks, and ultimately the vertical connectivity (Kolbe et al, 2019; Zhi et al, 2019) of subsurface systems. The “flushing” export patterns has been observed not only for nitrate but also for other solutes that are enriched in shallow soils and depleted in deeper subsurface, including dissolved organic carbon (DOC) (Moatar, Abbott, Minaudo, Curie, & Pinay, 2017; Musolff et al, 2017; Trauth et al, 2018; Zarnetske, Bouda, Abbott, Saiers, & Raymond, 2018). At the Naizin catchment, however, nitrate shows a unique pattern that has both high (May–June) and low (September–October) nitrate concentrations at low flow (Figure 1b).…”

Section: Discussionmentioning

confidence: 99%

Nitrate removal and young stream water fractions at the catchment scale

Benettin

Fovet

2020

Hydrological Processes

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Despite extensive research on nitrate export and removal, nutrient contamination remains a major threat to water bodies worldwide. At the local scale, nitrate removal is governed by biogeochemical conditions that vary in space and time, making integration to entire landscapes critical. Water transit times have often been used to describe solute transport, but the relation between water age and nitrate removal at the catchment scale is still poorly understood. We test the hypothesis that nitrate removal peaks when the fraction of young water in discharge is at its minimum, because nitrate removal occurs mostly under dry conditions where deeper, older groundwater dominates streamflow. We tested this hypothesis by exploring a detailed water quality record from the Kervidy-Naizin catchment (FR) and comparing the dynamics of nitrate to those of a conservative solute (chloride). We find that estimates of nitrate removal are consistent with previous estimates at the site and they show a good (inverse) correlation with the fraction of streamflow that is younger than 2.5 months. However, this young water fraction cannot be used to predict nitrate removal in the winter-spring period, when no removal is observed regardless of streamflow age. While this leads us to reject our hypothesis during the winter period, it also suggests that water age distributions and their correlation with nitrate removal can possibly reveal distinct sources of stream water at different hydrologic regimes and relevant biogeochemical reactions. K E Y W O R D Sagricultural catchment, chloride transport, denitrification, Naizin, nitrate removal, SAS function, water age, young water fraction

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Section: Discussionmentioning

confidence: 99%

Nitrate removal and young stream water fractions at the catchment scale

Benettin

Fovet

2020

Hydrological Processes

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“…Similarly, the abundance of soil bacteria has been suggested to vary with soil depth, with the highest abundance and microbial diversity present in the organic rich top soils (Fierer et al 2003). This suggests that conceptual models developed for the mobilization of DOC from soils to streams (Boyer et al 1996;Laudon et al 2011;Weiler and McDonnell 2006;Zarnetske et al 2018) could potentially also be applied to explain the variation in bacterial abundances in streams in the future. Nevertheless, the high ratio between soil-stream interfaces and water volume in headwater streams promotes transfer from soil to streams but the relationship might be weaker in larger fluvial systems.…”

Section: Discussionmentioning

confidence: 99%

Dynamic transfer of soil bacteria and dissolved organic carbon into small streams during hydrological events

Caillon

Schelker

2020

Aquat Sci

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Small headwater streams interlink catchment soils with the river network. As water makes its way from the hillslopes to the stream, it may transport dissolved organic carbon (DOC) and potentially soil microbes into stream water. In this study, we aimed at quantifying the dynamic transfer of DOC and microbial life, namely bacteria from catchment soils into streams. We hypothesized that increased soil saturation enhances the lateral inflow of bacteria and DOC into streams. To address this hypothesis, we sampled six first order streams and three soil transects at two different depths located within the pre-alpine Oberer Seebach (OSB) catchment in Austria over a duration of 2 years. We found a strong variation in DOC concentrations (range 0.4-5.6 mg L −1 ) and bacterial abundances (range < 500,000-3,863,000 cells mL −1 ) measured by flow-cytometry. The highest values of DOC and bacterial cells occurred during high flow events. DOC concentration and bacterial abundance were correlated across all streams and seasons. In soils, DOC ranges were higher and were also correlated with bacterial abundance, while DOC concentrations were ∼ 10 times higher per bacterial cell than in streams. Overall we show that soils provide a dynamic inflow of bacteria and DOC to first order streams. Most probably, this results in a dynamic and reoccurring inoculation of small streams from catchment soils during runoff events. We propose that this dynamic microbial inoculation of small streams is potentially relevant for microbial community dynamics of downstream receiving waters.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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“…The goodness of fit and the parameter estimation significance were assessed based on the coefficient of determination (R 2 ) and the P value. As in other studies (e.g., Vaughan et al, 2017;Zarnetske et al, 2018), our models did not account for potential temporal autocorrelation of the data.…”

Section: Discussionmentioning

confidence: 99%

Alpine Glacier Shrinkage Drives Shift in Dissolved Organic Carbon Export From Quasi‐Chemostasis to Transport Limitation

Canadell

Escoffier

Ulseth

et al. 2019

Geophysical Research Letters

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The export of dissolved organic carbon (DOC) from catchments is considered as an important energy flux through streams and a major connection between terrestrial and aquatic systems. However, the impact that predicted hydrological changes due to glacier retreat and reduction in snow cover changes will have on DOC export from high‐mountain streams remains unclear. In this study, we measured daily runoff and DOC yield during 1 year in Alpine streams draining catchments with different levels of glacier coverage. DOC yield showed a varied response to runoff across the catchments and varied seasonally as a function of the degree of glaciation and vegetation cover. Using space‐for‐time substitution, our results indicate that the controls on DOC yield from Alpine catchments change from chemostasis to transport limitation as glaciers shrink.

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Generality of Hydrologic Transport Limitation of Watershed Organic Carbon Flux Across Ecoregions of the United States

Cited by 165 publications

References 85 publications

Nitrate removal and young stream water fractions at the catchment scale

Nitrate removal and young stream water fractions at the catchment scale

Dynamic transfer of soil bacteria and dissolved organic carbon into small streams during hydrological events

Alpine Glacier Shrinkage Drives Shift in Dissolved Organic Carbon Export From Quasi‐Chemostasis to Transport Limitation

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