Hydrological pulses and burning of dissolved organic carbon by stream respiration

Demars, Benoît O. L.

doi:10.1002/lno.11048

Cited by 57 publications

(107 citation statements)

References 104 publications

(189 reference statements)

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“…). Soil water, groundwater, and stream water have very low soluble reactive phosphorus concentrations (5 μg P/L; Demars ) independently of discharge variability. The streams were about 0.8–1.0 m wide in the studied sections and their channels significantly undercut the banks by 30–46% of stream width.…”

Section: Methodsmentioning

confidence: 99%

“…DOM was the dominant flux of organic carbon (98%) under stable flows with average concentrations of 9.3 ± 1.7 mg C/L in the two studied streams (Demars ). This DOM was of terrestrial origin as shown by δ 13 C analyses of the natural DOM against terrestrial and aquatic plant material (Stutter et al.…”

Section: Methodsmentioning

confidence: 99%

“…). The pool of particulate organic carbon in the sediment is very small (Demars ), and coarse particulate organic carbon was less than 10 g C/m 2 .…”

Section: Methodsmentioning

confidence: 99%

“…, Marin‐Spiotta et al. , Demars ). This can explain the rapid turnover of allochthonous organic matter in aquatic ecosystems once it leaves the soil matrix (e.g., Marin‐Spiotta et al.…”

Section: Introductionmentioning

confidence: 99%

“…Here we test how a small addition of labile organic carbon (sucrose, C 12 H 22 O 11 ) affects the strength and dynamics of the autotroph–bacteria reciprocal carbon subsidies in phosphorus‐poor streams draining soils rich in organic carbon. The time scale of the experiment (three weeks) corresponded to a pulse of soil derived DOM during a period of hydrological connectivity (wet soils) known to drive stream heterotrophic respiration in the studied streams (Demars ). We expected sucrose addition to (1) weaken reciprocal carbon exchanges between autotrophs and bacteria (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Pulse of dissolved organic matter alters reciprocal carbon subsidies between autotrophs and bacteria in stream food webs

Demars

Friberg

Thornton

2020

Ecological Monographs

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Citation: Demars, B. O. L., N. Friberg, and B. Thornton. 2020. Pulse of dissolved organic matter alters reciprocal carbon subsidies between autotrophs and bacteria in stream food webs. Ecological Monographs 90(1):Abstract. Soils are currently leaching out dissolved organic matter (DOM) at an increasing pace due to climate and land use change or recovery from acidification. The implications for stream biogeochemistry and food webs remain largely unknown, notably the metabolic balance (biotic CO 2 emissions) and carbon cycling between autotrophs and bacteria. We increased by 12% the flux of DOM in a stream for three weeks to mimic a pulse of natural DOM supply from soils rich in organic matter. We were able to track its fate into the food web through the use of a before and after control impact experimental design and the addition of DOM with a distinctive d 13 C signature. We used whole-stream metabolism to quantify carbon fluxes. Both photosynthesis and heterotrophic respiration increased rapidly following C addition, but this was short lived, likely due to nutrient limitations. Carbon exchange between autotrophs and bacteria in the control stream accounted for about 49% of bacterial production and 37% of net primary production, under stable flow conditions. Net primary production relied partly (19% in the control) on natural allochthonous dissolved organic carbon via the CO 2 produced by bacterial respiration, intermingling the green and brown webs. The preferential uptake of labile carbon by bacteria and excess bacterial CO 2 relative to nutrients (N, P) for autotrophs shifted the reciprocal carbon exchange between bacteria and autotrophs to a predominantly one-way carbon flow from bacteria to autotrophs, increasing the C:N:P molar ratios of autotrophs, the latter likely to become less palatable to consumers. The bacterial response to sucrose addition shifted the metabolic balance toward heterotrophy increasing biotic CO 2 emissions (+125%), shortened the average distance travelled by a molecule of organic matter (À40%), and thus provided less organic matter of lower quality for downstream ecosystems. Even a small increase in labile dissolved organic matter supply due to climate and land use change could significantly alter in-stream carbon cycling, with large effects on stream food web and biogeochemistry in small streams draining catchments with soils rich in organic carbon.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…). The pool of particulate organic carbon in the sediment is very small (Demars ), and coarse particulate organic carbon was less than 10 g C/m 2 .…”

Section: Methodsmentioning

confidence: 99%

“…, Marin‐Spiotta et al. , Demars ). This can explain the rapid turnover of allochthonous organic matter in aquatic ecosystems once it leaves the soil matrix (e.g., Marin‐Spiotta et al.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pulse of dissolved organic matter alters reciprocal carbon subsidies between autotrophs and bacteria in stream food webs

Demars

Friberg

Thornton

2020

Ecological Monographs

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Forest management influences the effects of streamside wet areas on stream ecosystems

Erdozain

Emilson

Kreutzweiser

et al. 2020

Ecological Applications

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Riparian zones contain areas of strong hydrological connectivity between land and stream, referred to as variable source areas (VSAs), and are considered biogeochemical control points. However, little is known about whether VSAs influence stream communities and whether this connectivity is affected by forest management. To address this, we used multiple biotic and abiotic indicators to (1) examine the influence of VSAs on riparian vegetation and stream ecosystems by comparing VSA and non-VSA reaches and (2) explore how forest management may affect the influence of VSAs on stream ecosystems. We detected some significant differences between VSA and non-VSA reaches in the riparian vegetation (greater understory and lower tree density) and stream ecosystem indicators (greater dissolved organic matter aromaticity, microbial biomass, peroxidase activity and collector-gatherer density, and lower dissolved organic carbon concentrations, algal biomass, and predatory macroinvertebrate density), which suggests that VSAs may create a more heterotrophic ecosystem locally. However, we show some evidence that forest management activities (specifically, road density) can alter the influence of VSAs and eliminate the differences observed at lower forest management intensities, and that the most hydrologically connected areas seem more sensitive to disturbance. Therefore, we suggest that the heterogeneity in hydrological connectivity along riparian zones should be considered when planning forest harvesting operations and road building (e.g., wider riparian buffers around VSAs).

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Patterns and Drivers of Dissolved Gas Concentrations and Fluxes Along a Low Gradient Stream

Carter

DelVecchia

Bernhardt

2022

Preprint

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Freshwater ecosystems are globally significant sources of greenhouse gases (GHG) to the atmosphere. Generally, we assume that in-situ production of GHG in streams is limited by turbulent reaeration and high dissolved oxygen concentrations, so stream GHG flux is highest in headwater streams that are connected to their watersheds and serve as conduits for the release of terrestrially derived GHG. Low-gradient streams contain pool structures with longer residence times conducive to the in-situ production of GHG, but these streams, and the longitudinal heterogeneity therein, are seldom studied. We measured continuous ecosystem metabolism alongside concentrations and fluxes of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) from autumn to the following spring along an eight kilometer segment of a low-gradient third order stream in the North Carolina Piedmont. We characterized spatial and temporal patterns of GHG in the context of channel geomorphology, hydrology, and ecosystem metabolic rates using linear mixed effects models. We found that stream metabolic cycling was responsible for most of the CO 2 flux over this period, and that in-channel aerobic metabolism was a primary driver of both CH 4 and N 2 O fluxes as well. Long water residence times, limited reaeration, and substantial organic matter from terrestrial inputs foster conditions conducive to the in-stream accumulation of CO 2 and CH 4 from microbial respiration. Streams like this one are common in landscapes with low topographic relief, making it likely that the high contribution of instream metabolism to GHG fluxes that we observed is a widespread yet understudied behavior of many small streams.

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Hydrological pulses and burning of dissolved organic carbon by stream respiration

Cited by 57 publications

References 104 publications

Pulse of dissolved organic matter alters reciprocal carbon subsidies between autotrophs and bacteria in stream food webs

Pulse of dissolved organic matter alters reciprocal carbon subsidies between autotrophs and bacteria in stream food webs

Forest management influences the effects of streamside wet areas on stream ecosystems

Patterns and Drivers of Dissolved Gas Concentrations and Fluxes Along a Low Gradient Stream

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