Temperature Dependence of Photodegradation of Dissolved Organic Matter to Dissolved Inorganic Carbon and Particulate Organic Carbon

Porcal, Petr; Dillon, Peter J.; Molot, Lewis A.

doi:10.1371/journal.pone.0128884

Cited by 62 publications

(45 citation statements)

References 36 publications

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“…For example, we found that contributions of in situ transformation were positively correlated with water temperature (Figures 4C,D). This relationship corresponds with the observed temperature dependence of both bacterial decomposition and Colorado River Decrease in lower section 2300Miller, 2012 photochemical oxidation (Davidson and Janssens, 2006;Porcal et al, 2015)-the two major pathways for in situ DOC loss in aquatic systems (Cole et al, 2007). The lower coefficient of correlation between DOC concentration and temperature in the UMR (4c) was probably due to additional DOC loss pathways, such as sorption onto particles (Aufdenkampe et al, 2001), DOC flocculation (Benedetti et al, 2003) and exchanges with floodplains (Tockner et al, 1999).…”

Section: Tributary Inputs As a Dominant Control On The Doc Longitudinsupporting

confidence: 73%

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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Section: Tributary Inputs As a Dominant Control On The Doc Longitudinsupporting

confidence: 73%

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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“…A sharp decrease in POC concentrations at low salinity has been reported in the Lena delta region and was attributed to sinking of particles (Cauwet and Sidorov, 1996). We speculate that the main drivers on the apparent removal of highly humic content DOM observed within the surface layer are the photodegradation and flocculation, given the high susceptibility of those aromatic carbons to those processes (von Wachenfeldt et al, 2008;Porcal et al, 2013Porcal et al, , 2015Asmala et al, 2014;Helms et al, 2014). Those processes have also been indicated to modulate the non-conservative mixing behavior in other estuaries such as the Mississippi delta (Benner and Opsahl, 2001).…”

Section: Dynamics and Fate Of Dom In The Lena Delta Regionsupporting

confidence: 54%

“…Furthermore, the influence of particulate matter and sediments in coastal and shelf environments has to be taken into account given their influence on DOM removal through the process of sorption and flocculation (Uher et al, 2001;Shank et al, 2005;Guo et al, 2007;Asmala et al, 2014). The flocculation process, in turn, can be increased either due to the presence of the salt in the marine water (Asmala et al, 2014, and references therein) and to the exposition to high light intensities that, together with photochemical processes, can synergistically enhance the DOM removal from the dissolved phase (von Wachenfeldt et al, 2008;Porcal et al, 2013Porcal et al, , 2015. A sharp decrease in POC concentrations at low salinity has been reported in the Lena delta region and was attributed to sinking of particles (Cauwet and Sidorov, 1996).…”

Section: Dynamics and Fate Of Dom In The Lena Delta Regionmentioning

confidence: 99%

“…In coastal regions, especially in areas close to river outflows, the riverine input, and its mixing with marine waters are the major factors controlling the distribution and composition of DOM (Stedmon and Markager, 2003;Guo et al, 2007;Alling et al, 2010). In these waters processes such as photobleaching (Opsahl and Benner, 1998;Stubbins et al, 2006;Helms et al, 2008Helms et al, , 2014Porcal et al, 2013Porcal et al, , 2015, sorption to sediments, flocculation (Uher et al, 2001;Shank et al, 2005;Guo et al, 2007;von Wachenfeldt et al, 2008;Asmala et al, 2014), biological uptake (Boyd and Osburn, 2004), biological release (Romera-Castillo et al, 2010), and photo-production of DOM (Helms et al, 2014) can also play a crucial role in controlling the amount, composition, and reactivity of DOM in these environments.…”

Section: Introductionmentioning

confidence: 99%

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From Fresh to Marine Waters: Characterization and Fate of Dissolved Organic Matter in the Lena River Delta Region, Siberia

et al. 2015

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Connectivity between the terrestrial and marine environment in the Artic is changing as a result of climate change, influencing both freshwater budgets, and the supply of carbon to the sea. This study characterizes the optical properties of dissolved organic matter (DOM) within the Lena Delta region and evaluates the behavior of DOM across the fresh water-marine gradient. Six fluorescent components (four humic-like; one marine humic-like; one protein-like) were identified by Parallel Factor Analysis (PARAFAC) with a clear dominance of allochthonous humic-like signals. Colored DOM (CDOM) and dissolved organic carbon (DOC) were highly correlated and had their distribution coupled with hydrographical conditions. Higher DOM concentration and degree of humification were associated with the low salinity waters of the Lena River. Values decreased toward the higher salinity Laptev Sea shelf waters. Results demonstrate different responses of DOM mixing in relation to the vertical structure of the water column, as reflecting the hydrographical dynamics in the region. Two mixing curves for DOM were apparent. In surface waters above the pycnocline there was a sharper decrease in DOM concentration in relation to salinity indicating removal. In the bottom water layer the DOM decrease within salinity was less. We propose there is a removal of DOM occurring primarily at the surface layer, which is likely driven by photodegradation and flocculation.

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“…The fate of photo-oxidized DOM depends on temperature. For example, at lower temperatures DOM is generally oxidized directly into CO 2 , whereas at higher temperatures DOM is broken into intermediate molecules prior to mineralization into CO 2 (Porcal et al, 2015). In some cases, the alteration of DOM molecular structure via photo-oxidation (e.g., Rodríguez-Zuniga et al, 2008) can result in enhanced biological decomposition (Tranvik and Bertilsson, 2001;Cory et al, 2007Cory et al, , 2014Judd et al, 2007).…”

Section: Estuarine Om Transport Burial and Transformationmentioning

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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Temperature Dependence of Photodegradation of Dissolved Organic Matter to Dissolved Inorganic Carbon and Particulate Organic Carbon

Cited by 62 publications

References 36 publications

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

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

From Fresh to Marine Waters: Characterization and Fate of Dissolved Organic Matter in the Lena River Delta Region, Siberia

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

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