An initial SPARROW model of land use and in-stream controls on total organic carbon in streams of the conterminous United States

Shih, Jhih‐Shyang; Alexander, Richard B.; Smith, Richard A.; Boyer, Elizabeth W.; Shwarz, Grogory E.; Chung, Susie

doi:10.3133/ofr20101276

Cited by 30 publications

(43 citation statements)

References 25 publications

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“…The difference between results and those reported earlier [46] may be caused by the higher phosphorus concentrations in U.S. rivers, which enhances in-stream primary production. Our findings are consistent with the conclusions of [68,69] that algae growth can be an important source of riverine organic carbon. Our results also suggest that chemical fertilizer use may alter carbon cycling across the terrestrial-aquatic interface by enhancing algae growth in aquatic ecosystems.…”

Section: Environmental Controls On Doc Concentrationssupporting

confidence: 92%

An Analysis of Terrestrial and Aquatic Environmental Controls of Riverine Dissolved Organic Carbon in the Conterminous United States

Yang

Zhang

et al. 2017

Water

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Analyses of environmental controls on riverine carbon fluxes are critical for improved understanding of the mechanisms regulating carbon cycling along the terrestrial-aquatic continuum.Here, we compile and analyze riverine dissolved organic carbon (DOC) concentration data from 1402 United States Geological Survey (USGS) gauge stations to examine the spatial variability and environmental controls of DOC concentrations in the United States (U.S.) surface waters. DOC concentrations exhibit high spatial variability in the U.S., with an average of 6.42 ± 6.47 mg C/L (Mean ± Standard Deviation). High DOC concentrations occur in the Upper Mississippi River basin and the southeastern U.S., while low concentrations are mainly distributed in the western U.S. Soil properties such as soil organic matter, soil water content, and soil sand content mainly show positive correlations with DOC concentrations; forest and shrub land have positive correlations with DOC concentrations, but urban area and cropland demonstrate negative impacts; and total instream phosphorus and dam density correlate positively with DOC concentrations. Notably, the relative importance of these environmental controls varies substantially across major U.S. water resource regions. In addition, DOC concentrations and environmental controls also show significant variability from small streams to large rivers. In sum, our results reveal that general multi-linear regression of twenty environmental factors can partially explain (56%) the DOC concentration variability. This study also highlights the complexity of the interactions among these environmental factors in determining DOC concentrations, thus calls for processes-based, non-linear methodologies to constrain uncertainties in riverine DOC cycling.

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Section: Environmental Controls On Doc Concentrationssupporting

confidence: 92%

An Analysis of Terrestrial and Aquatic Environmental Controls of Riverine Dissolved Organic Carbon in the Conterminous United States

Yang

Zhang

et al. 2017

Water

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“…To constrain inputs of organic carbon across the landward boundary, we used load estimates of total organic carbon (TOC) from the SPARROW (Spatially Referenced Regression on Watershed Attributes) water quality model developed by the USGS [ Smith et al ., ; Shih et al ., ]. The USGS maintains an extensive network of stream monitoring stations with continuous flow measurements and intermittent concentration measurements for various water quality constituents, including TOC.…”

Section: Methodsmentioning

confidence: 99%

“…The SPARROW long‐term average TOC fluxes used in this study are based on model application to the drainages of the estuaries using streamflow and TOC concentrations measurements from 1969 to 2008 and land use data from the 1992 National Land Cover Data Set (NLCD) [ Shih et al ., ]. The 1992 NLCD does not differentiate between tidal and nontidal wetland types, so in the Shih et al .…”

Section: Methodsmentioning

confidence: 99%

Net ecosystem production and organic carbon balance of U.S. East Coast estuaries: A synthesis approach

Herrmann

Najjar

Kemp

et al. 2015

Global Biogeochemical Cycles

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108

105

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Net ecosystem production (NEP) and the overall organic carbon budget for the estuaries along the East Coast of the United States are estimated. We focus on the open estuarine waters, excluding the fringing wetlands. We developed empirical models relating NEP to loading ratios of dissolved inorganic nitrogen to total organic carbon, and carbon burial in the sediment to estuarine water residence time and total nitrogen input across the landward boundary. Output from a data-constrained water quality model was used to estimate inputs of total nitrogen and organic carbon to the estuaries across the landward boundary, including fluvial and tidal-wetland sources. Organic carbon export from the estuaries to the continental shelf was computed by difference, assuming steady state. Uncertainties in the budget were estimated by allowing uncertainties in the supporting model relations. Collectively, U.S. East Coast estuaries are net heterotrophic, with the area-integrated NEP of À1.5 (À2.8, À1.0) Tg C yr À1 (best estimate and 95% confidence interval) and area-normalized NEP of. East Coast estuaries serve as a source of organic carbon to the shelf, exporting 3.4 (2.0, 4.3) Tg C yr À1 or 7.6 (4.4, 9.5) mol C m À2 yr À1. Organic carbon inputs from fluvial and tidal-wetland sources for the region are estimated at 5.4 (4.6, 6.5) Tg C yr À1 or 12 (10, 14) mol C m À2 yr À1 and carbon burial in the open estuarine waters at 0.50 (0.33, 0.78) Tg C yr À1 or 1.1 (0.73, 1.7) mol C m À2 yr À1. Our results highlight the importance of estuarine systems in the overall coastal budget of organic carbon, suggesting that in the aggregate, U.S. East Coast estuaries assimilate (via respiration and burial)~40% of organic carbon inputs from fluvial and tidal-wetland sources and allow~60% to be exported to the shelf.

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“…Historical Wetland Loss and Effect on Mississippi Watershed C and N A significant fraction of wetland extent in the UMR has been lost during the last few centuries due to large-scale conversion of wetlands to farmlands in the Ohio/MR Valleys and dam constructions in the UMR for navigation (Shih et al, 2010). In the LMR, a large fraction of floodplain wetlands have also been replaced with arable land, and human-made levees have resulted in a reduction of about 90% of the local inputs from the remaining floodplain wetlands in the region (Wiener et al, 1996).…”

Section: Wetland Distribution Effects On River Doc Longitudinal Patternsmentioning

confidence: 99%

Impact of Wetland Decline on Decreasing Dissolved Organic Carbon Concentrations along the Mississippi River Continuum

Duan

Kaushal

et al. 2017

Front. Mar. Sci.

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Prior to discharging to the ocean, large rivers constantly receive inputs of dissolved organic carbon (DOC) from tributaries or fringing floodplains and lose DOC via continuous in situ processing along distances that span thousands of kilometers. Current concepts predicting longitudinal changes in DOC mainly focus on in situ processing or exchange with fringing floodplain wetlands, while effects of heterogeneous watershed characteristics are generally ignored. We analyzed results from a 17-year time-series of DOC measurements made at seven sites and three expeditions along the entire Mississippi River main channel with DOC measurements made every 17 km. The results show a clear downstream decrease in DOC concentrations that was consistent throughout the entire study period. Downstream DOC decreases were primarily (∼63-71%) a result of constant dilutions by low-DOC tributary water controlled by watershed wetland distribution, while in situ processing played a secondary role. We estimate that from 1780 to 1980 wetland loss due to land-use alterations caused a ca. 58% decrease in in DOC concentrations in the tributaries of the Mississippi River. DOC reductions caused by watershed wetland loss likely impacted the capacity for the river to effectively remove nitrogen via denitrification, which can further exacerbate coastal hypoxia. These findings highlight the importance of watershed wetlands in regulating DOC longitudinally along the headland to ocean continuum of major rivers.

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An initial SPARROW model of land use and in-stream controls on total organic carbon in streams of the conterminous United States

Cited by 30 publications

References 25 publications

An Analysis of Terrestrial and Aquatic Environmental Controls of Riverine Dissolved Organic Carbon in the Conterminous United States

An Analysis of Terrestrial and Aquatic Environmental Controls of Riverine Dissolved Organic Carbon in the Conterminous United States

Net ecosystem production and organic carbon balance of U.S. East Coast estuaries: A synthesis approach

Impact of Wetland Decline on Decreasing Dissolved Organic Carbon Concentrations along the Mississippi River Continuum

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