Positive priming of terrestrially derived dissolved organic matter in a freshwater microcosm system

Bianchi, Thomas S.; Thornton, Daniel C. O.; Yvon‐Lewis, S. A.; King, Gary M.; Eglinton, T. I.; Shields, Michael R.; Ward, Nicholas D.; Curtis, Jason H.

doi:10.1002/2015gl064765

Cited by 99 publications

(76 citation statements)

References 31 publications

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“…Although this effect has been the subject of intensive study in soils, it has only recently begun to attract substantial attention in aquatic systems (Guenet et al, 2010;Bianchi, 2011;Bianchi et al, 2015). Among aquatic systems, the priming effect may be particularly relevant in estuaries, where labile organic matter (OM, for instance autochthonous production) mixes with more recalcitrant OM, such as aged terrestrial OM and recalcitrant marine OM (Guenet et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…Several studies using unlabeled labile organic matter to aquatic ecosystems showed by mass balance that additions of labile OM must have stimulated oxidation of more recalcitrant OM (De Haan, 1977;Shimp and Pfaender, 1985;Farjalla et al, 2009); other investigators in freshwater environments have not found evidence for the priming effect (Bengtsson et al, 2014;Catalán et al, 2015), while Bianchi et al (2015) observed priming of an estuarine bacterial isolate of Acinetobacter induced by a disaccharide or algal exudate. With the exception of Farjalla et al (2009), which concerns a tropical lagoon, these studies were not performed in estuaries.…”

Section: Introductionmentioning

confidence: 99%

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Evidence for the Priming Effect in a Planktonic Estuarine Microbial Community

2016

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The "priming effect," in which addition of labile substances changes the remineralization rate of recalcitrant organic matter, has been intensively studied in soils, but is less well-documented in aquatic systems. We investigated the extent to which additions of nutrients or labile organic carbon could influence remineralization rates of 14 C-labeled, microbially-degraded, phytoplankton-derived organic matter (OM) in microcosms inoculated with microbial communities drawn from Grove Creek Estuary in coastal Georgia, USA. We found that amendment with labile protein plus phosphorus increased remineralization rates of degraded, phytoplankton-derived OM by up to 100%, whereas acetate slightly decreased remineralization rates relative to an unamended control. Addition of ammonium and phosphate induced a smaller effect, whereas addition of ammonium alone had no effect. Counterintuitively, alkaline phosphatase activities increased in response to the addition of protein under P-replete conditions, indicating that production of enzymes unrelated to the labile priming compound may be a mechanism for the priming effect. The observed priming effect was transient: after 36 days of incubation roughly the same quantity of organic carbon had been mineralized in all treatments including no-addition controls. This timescale is on the order of the typical hydrologic residence times of well-flushed estuaries suggesting that priming in estuaries has the potential to influence whether OC is remineralized in situ or exported to the coastal ocean.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evidence for the Priming Effect in a Planktonic Estuarine Microbial Community

2016

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“…For example, in more naturally flowing systems that have higher connectivity to floodplain wetlands, like the Amazon River, DOC increases downstream concurrent with high rates of in situ processing as a result of floodplain wetland inputs to the river (Hedges et al, 2000;Ward et al, 2015). Wetlands also play an important role in driving CO 2 production in large rivers (Abril et al, 2014;Borges et al, 2015) due to aquatic plant respiration and enhanced in situ processing due to both breakdown of wetland-derived OC and processes, such as priming effects, which can stimulate the breakdown of terrestrially-derived OC in the presence of fresh autochthonous OC (Guenet et al, 2014;Bianchi et al, 2015;Ward et al, 2016). In contrast, in rivers where wetlands are primarily located in headwater sub-watersheds and floodplain wetland extent is limited (as a result of human development; Wiener et al, 1996), such as the MR (Figure 1), DOC concentrations decrease gradually from headwaters to the river mouth due to tributary dilution.…”

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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“…For example, in the Amazon River the breakdown of vascular plant-derived OM to CO 2 is enhanced by as much as 6-fold when algaerich tributaries mix with the sediment and terrestrially-derived OM-rich main channel . This phenomenon, referred to as the priming effect, has been well studied in soils (Löhnis, 1926;Kuzyakov et al, 2000), but has only recently received attention from aquatic scientists (Aller et al, 1996;Guenet et al, 2014;Bianchi et al, 2015). It is hypothesized that this process plays an important role on OM decomposition across a wide range of settings such as estuaries (Steen et al, 2015), coastal oceans, river plumes (Aller et al, 1996), natural and manmade reservoirs, the hyporheic zone, and lower rivers (Bianchi, 2011).…”

Section: Introductionmentioning

confidence: 99%

Where Carbon Goes When Water Flows: Carbon Cycling across the Aquatic Continuum

et al. 2017

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The purpose of this review is to highlight progress in unraveling carbon cycling dynamics across the continuum of landscapes, inland waters, coastal oceans, and the atmosphere. Earth systems are intimately interconnected, yet most biogeochemical studies focus on specific components in isolation. The movement of water drives the carbon cycle, and, as such, inland waters provide a critical intersection between terrestrial and marine biospheres. Inland, estuarine, and coastal waters are well studied in regions near centers of human population in the Northern hemisphere. However, many of the world's large river systems and their marine receiving waters remain poorly characterized, particularly in the tropics, which contribute to a disproportionately large fraction of the transformation of terrestrial organic matter to carbon dioxide, and the Arctic, where positive feedback mechanisms are likely to amplify global climate change. There are large gaps in current coverage of environmental observations along the aquatic continuum. For example, tidally-influenced reaches of major rivers and near-shore coastal regions around river plumes are often left out of carbon budgets due to a combination of methodological constraints and poor data coverage. We suggest that closing these gaps could potentially alter global estimates of CO 2 outgassing from surface waters to the atmosphere by several-fold. Finally, in order to identify and constrain/embrace uncertainties in global carbon budget estimations it is important that we further adopt statistical and modeling approaches that have become well-established in the fields of oceanography and paleoclimatology, for example.

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Positive priming of terrestrially derived dissolved organic matter in a freshwater microcosm system

Cited by 99 publications

References 31 publications

Evidence for the Priming Effect in a Planktonic Estuarine Microbial Community

Evidence for the Priming Effect in a Planktonic Estuarine Microbial Community

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

Where Carbon Goes When Water Flows: Carbon Cycling across the Aquatic Continuum

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