Biological and land use controls on the isotopic composition of aquatic carbon in the Upper Mississippi River Basin

Voß, Britta; Wickland, Kimberly P.; Aiken, George R.; Striegl, Robert G.

doi:10.1002/2017gb005699

Cited by 28 publications

(32 citation statements)

References 98 publications

(137 reference statements)

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“…However, this application can be complicated by the presence of additional biogeochemical transformations influencing the observed δ 13 C‐DIC values. The influence of CO 2 evasion on δ 13 C‐DIC values has been documented in soils (Amundson et al, ; Cerling et al, ; Davidson, ), larger river systems (Giesler et al, ; Hélie et al, ; Voss et al, ), and headwater streams (Amiotte‐Suchet et al, ; Doctor et al, ; van Geldern et al, ), but it is likely that the patterns in δ 13 C‐DIC values simultaneously reflect a larger range of sources and processes (Campeau, Wallin, et al, ).…”

Section: Introductionmentioning

confidence: 99%

Stable Carbon Isotopes Reveal Soil‐Stream DIC Linkages in Contrasting Headwater Catchments

et al. 2018

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Large CO2 evasion to the atmosphere occurs as dissolved inorganic carbon (DIC) is transported from soils to streams. While this physical process has been the focus of multiple studies, less is known about the underlying biogeochemical transformations that accompany this transfer of C from soils to streams. Here we used patterns in stream water and groundwater δ13C‐DIC values within three headwater catchments with contrasting land cover to identify the sources and processes regulating DIC during its transport. We found that although considerable CO2 evasion occurs as DIC is transported from soils to streams, there were also other processes affecting the DIC pool. Methane production and mixing of C sources, associated with different types and spatial distribution of peat‐rich areas within each catchment, had a significant influence on the δ13C‐DIC values in both soils and streams. These processes represent an additional control on δ13C‐DIC values and the catchment‐scale cycling of DIC across different northern landscape types. The results from this study demonstrate that the transport of DIC from soils to streams results in more than just rapid CO2 evasion to the atmosphere but also represents a channel of C transformation, which questions some of our current conceptualizations of C cycling at the landscape scale.

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Section: Introductionmentioning

confidence: 99%

Stable Carbon Isotopes Reveal Soil‐Stream DIC Linkages in Contrasting Headwater Catchments

et al. 2018

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“…Voss et al [41] showed that in-stream processes such as respiration and photosynthesis were primary drivers determining δ 13 C DIC values, and that in-stream signatures were distinct from their source signatures. The discrepancy between the expected and reported δ 13 C DIC values for the RR could be indicative of the importance of in-stream respiration in its warm waters, which causes more negative values through the removal of 13 C from the aquatic carbon pool [25].…”

Section: Sources and Processes Determining Dissolved Inorganic Carbonmentioning

confidence: 99%

“…The MR and RR's relative influences on organic carbon isotopic signatures in the AR should then be closer to a 1:1 mixing ratio. δ 13 C DOC values retain information about terrestrial sources [41], so although the flow of the MR dominates the AR, organic carbon in the AR can be expected to be highly reflective of the organic material that is found in the soils of the RR basin. In a recent study of isotope signatures in the upper MR, Voss et al, [41] revealed that δ 13 C DOC values became more negative with increased forest cover.…”

Section: Differences In Dissolved Organic Carbon Sources Entering the Armentioning

confidence: 99%

“…δ 13 C DOC values retain information about terrestrial sources [41], so although the flow of the MR dominates the AR, organic carbon in the AR can be expected to be highly reflective of the organic material that is found in the soils of the RR basin. In a recent study of isotope signatures in the upper MR, Voss et al, [41] revealed that δ 13 C DOC values became more negative with increased forest cover. This may further implicate the forested eastern region of the RR as the primary contributor of carbon in the RR.…”

Section: Differences In Dissolved Organic Carbon Sources Entering the Armentioning

confidence: 99%

“…The preferential use of atmospheric 12 C for photosynthetic processes gives fresh plant material a more negative signature; more negative δ 13 C DOC signatures in the RR could then also indicate higher concentrations of plant material or algal signatures as a consequence of higher in-stream primary production [41,49]. Additional information on the quality of riverine organic matter can be obtained by determination of chlorophyll a [50,51], which is derived from pigmented plant material and algal production.…”

Section: Differences In Dissolved Organic Carbon Sources Entering the Armentioning

confidence: 99%

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Unravelling the Relative Contribution of Dissolved Carbon by the Red River to the Atchafalaya River

DelDuco

2017

Water

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Abstract:The Atchafalaya River (AR), North America's largest swamp river, annually discharges a large volume of freshwater (nearly 200 km 3 ), delivering~25% of the Mississippi River's (MR) flow and the entire Red River's (RR) flow into the Gulf of Mexico. Studies have reported higher levels of organic carbon in the AR's outlets compared to the MR's outlet, raising questions about local carbon sources. In this study, we investigated dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) inputs into the AR from the RR and MR using DOC and DIC concentrations, mass loading, and isotopic signature (δ 13 C) analyses. Monthly river water sampling was conducted in the MR and RR near their confluence where the AR is formed from May 2015 to May 2016. DIC concentrations in the RR were found to be only half of those found in the MR, while the RR's DOC concentrations were on average 1.8 times higher than those found in the MR. Based on the models developed for this study period, the RR's contribution to DIC mass loading in the AR represented 1.41 teragrams (Tg) (or, 29.7%) of the total 4.76 Tg DIC transported by both tributaries, while its contribution to DOC mass loading was disproportionately high, accounting for 1.74 Tg of the 2.75 Tg DOC (or, 63.2% of total DOC) entering the AR. Both δ 13 C DIC and δ 13 C DOC showed significantly more negative values in the RR than those found in the MR. Significant correlation between δ 13 C DIC and δ 13 C DOC isotope values in the RR indicated interrelation of dissolved carbon processing, which was not observable in the MR. These results strongly suggest that the RR is an extremely significant source of DOC to the AR, and thus the Gulf of Mexico, and additionally plays an important role in diluting the anthropogenically enhanced DIC fluxes of the MR.

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Preservation methods for the isotopic composition of dissolved carbon species in non‐ideal conditions

Wilson

Munizzi

Erhardt

2020

Rapid Comm Mass Spectrometry

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The stable carbon isotope compositions of dissolved inorganic carbon (δ 13 C DIC) and dissolved organic carbon (δ 13 C DOC) are readily affected by postsampling microbial activity if not adequately preserved. Existing preservation methods require rapid chilling, analysis, and/or toxic chemicals, all challenging to use safely in the field and during remote field seasons. Therefore, a preservation method that is safe but also effective over a range of storage times is needed when sampling waters at very remote sites. Methods: Two samples, with different dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) concentrations, were filtered with a 0.2-μm filter and preserved with six different methods, mercuric chloride, copper sulfate, phosphoric acid, benzalkonium chloride, zinc chloride, hydrochloric acid, and a filter-only control. These samples were held at 4 C, 22 C, or 35 C. Regular measurement of the DIC and DOC δ 13 C values were made over the following 60 days for δ 13 C DIC and 66 days for δ 13 C DOC. Results: Over the course of the experiment, mercuric chloride, copper sulfate, zinc chloride, and benzalkonium chloride resulted in δ 13 C DIC fractionation at both 4 C and 22 C. Only filtering to 0.2 μm at the time of collection, with or without acidification with phosphoric acid, resulted in minimal isotopic fractionation at both 4 C and 22 C and over the entirety of the experiment. For δ 13 C DOC values, only filtering to 0.2 μm minimized fractionation for both bulk and vial storage over 66 days at 22 C. Conclusions: Filtering to 0.2 μm at the time of collection is more effective than the use of toxic chemicals for measuring δ 13 C DIC and δ 13 C DOC values. Phosphoric acid is as effective as only filtering for δ 13 C DIC and may be ideal depending on sampling considerations. These results demonstrate not only that water samples can be preserved for δ 13 C DIC and δ 13 C DOC analysis for long periods, but that preservation is best accomplished with non-toxic or low-toxicity methods. 1 | INTRODUCTION Knowledge of the concentration, composition, and consumption of carbon in aqueous systems is a powerful tool for understanding water movement, storage, and sources. In an aquatic ecosystem, water sourced from environments with high organic loads will typically have higher dissolved organic carbon (DOC) concentrations, along with stable carbon isotope ratios (δ 13 C values) reflective of the predominant photosynthetic pathway. 1 Conversely, water with extended contact with carbonate rocks typically has high dissolved inorganic carbon (DIC) concentrations, with δ 13 C values representative of soil and carbonate sources. 2 With time, the DOC can be consumed by biological and microbial activity, while the DIC can exchange with the organic carbon pool. 1 To be able to accurately characterize carbon sources and secondary processes, however, no additional alteration of samples can occur after collection. Without proper preservation,

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Biological and land use controls on the isotopic composition of aquatic carbon in the Upper Mississippi River Basin

Cited by 28 publications

References 98 publications

Stable Carbon Isotopes Reveal Soil‐Stream DIC Linkages in Contrasting Headwater Catchments

Stable Carbon Isotopes Reveal Soil‐Stream DIC Linkages in Contrasting Headwater Catchments

Unravelling the Relative Contribution of Dissolved Carbon by the Red River to the Atchafalaya River

Preservation methods for the isotopic composition of dissolved carbon species in non‐ideal conditions

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