Molecular-level changes of dissolved organic matter along the Amazon River-to-ocean continuum

Seidel, Michael; Yager, Patricia L.; Ward, Nicholas D.; Carpenter, Edward; Gomes, Helga do Rosário; Krusche, Alex V.; Richey, Jeffrey E.; Dittmar, Thorsten; Medeiros, Patricia M.

doi:10.1016/j.marchem.2015.06.019

Cited by 213 publications

(203 citation statements)

References 118 publications

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“…As such, compounds that decreased or increased in relative abundance had distinct chemical characteristics. There was a relative enrichment of molecules that occupy the upper left corner of the van Krevelen diagram after the incubation (Figure 2B), i.e., a shift toward low O/C and high H/C ratios, which is consistent with molecular transformations observed in dark incubations of DOM from the Amazon River mouth (Medeiros et al, 2015c;Seidel et al, 2015). Additionally, while formulae whose relative abundances strongly decreased after the incubation (i.e., more negative loadings of PC1 DOB−long in Figure 2B) were characterized by high masses (553.5 ± 78.7 Da), formulae whose relative abundances were enriched after the incubation (i.e., more positive PC1 DOB−long loading in Figure 2B) were characterized by significantly lower masses (286.0 ± 93.9 Da) ( Figure 3A and Table 1; Wilcoxon rank-sum test, p < 0.01).…”

Section: Dom Transformations At Doboy Soundsupporting

confidence: 76%

“…As riverine DOM is transported toward the ocean, its quantity and composition is often altered (Cole et al, 2007) by a variety of chemical, biological and physical processes (Tzortziou et al, 2008), making estuaries hot spots of DOM cycling. Significant gradients exist in the composition of DOM in estuaries (Sleighter and Hatcher, 2008;Medeiros et al, 2015c;Seidel et al, 2015). In general, DOC concentrations and the DOM aromaticity decrease toward the ocean (Abdulla et al, 2013) at the same time that DOM lability increases (D'Andrilli et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

“…Despite these challenges, much has been learned by tracking changes in DOC concentration and DOM composition during incubation experiments, including the variation in biomineralization rates as a function of DOM source (e.g., Moran and Zepp, 1997;Obernosterer and Benner, 2004), the relationship of microbial activity to the production of labile (e.g., Kawasaki and Benner, 2006) and refractory (e.g., Ogawa et al, 2001;Jiao et al, 2010;Lechtenfeld et al, 2015) DOM, and how bacterial-derived refractory material compares structurally to refractory DOM in the ocean (e.g., Osterholz et al, 2015). Studies using ultrahigh resolution mass spectrometry have revealed additional molecular-level transformations in DOM as a result of microorganism activity (Kujawinski et al, 2004), including a significant decrease in the molecular diversity of terrigenous DOM (Seidel et al, 2015) and a preferential degradation of oxygen-rich molecules on a time scale of several days (Kim et al, 2006;Medeiros et al, 2015c;Seidel et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Microbially-Mediated Transformations of Estuarine Dissolved Organic Matter

et al. 2017

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Microbially-mediated transformations of dissolved organic matter (DOM) in a marsh-dominated estuarine system were investigated at the molecular level using ultrahigh resolution mass spectrometry. In addition to observing spatial and temporal variability in DOM sources in the estuary, multiple incubations with endogenous microorganisms identified the influence of DOM composition on biodegradation. A clear microbial preference for degradation of compounds associated with marine DOM relative to those of terrestrial origin was observed, resulting in an overall shift of the remaining DOM toward a stronger terrigenous signature. During short, 1-day long incubations of samples rich in marine DOM, the molecular formulae that were enriched had slightly smaller mass (20-30 Da) and number of carbon atoms compared to the molecular formulae that were depleted. Over longer time scales (70 days), the mean differences in molecular mass between formulae that were depleted and enriched were substantially larger (∼270 Da). The differences in elemental composition over daily time scales were consistent with transformations in functional groups; over longer time scales, the differences in elemental composition may be related to progressive transformations of functional groups of intermediate products and/or other reactions. Our results infused new data toward the understanding of DOM processing by bacterioplankton in estuarine systems.

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Section: Dom Transformations At Doboy Soundsupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Microbially-Mediated Transformations of Estuarine Dissolved Organic Matter

et al. 2017

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“…Two recent studies have evaluated the evolution of DOM composition along the river to plume continuum of the Amazon River based on ultra-high resolution mass spectrometry measurements performed along the continuum and after week-long dark incubations (Medeiros et al, 2015a;Seidel et al, 2015a). DOM composition patterns suggested continuous transformation of DOM via removal of oxygen-rich aromatic terrestrial DOM and a relative enrichment of more aliphatic microbial and marine compounds, with an overall decrease in molecular formulae complexity (Figure 5).…”

Section: Estuarine Om Transport Burial and Transformationmentioning

confidence: 99%

“…For example, Feng et al (2016) evaluated changes in OM composition from Peruvian headwaters to marine sediments with comparisons to available data in the central reaches of the river. The lower reaches of the river, which represents 13% of the total basin area, have been unstudied until recently (Ward et al, 2015) and there has also been recent effort examining the evolution of OM and microbial communities from the river into the ocean plume (Medeiros et al, 2015a;Satinsky et al, 2015;Seidel et al, 2015a).…”

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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A novel molecular approach for tracing terrigenous dissolved organic matter into the deep ocean

Medeiros

Seidel

Niggemann

et al. 2016

Global Biogeochemical Cycles

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Marine dissolved organic matter (DOM) contains one of the largest exchangeable organic carbon pools on Earth. Riverine input represents an important source of DOM to the oceans, yet much remains to be learned about the fate of the DOM linking terrestrial to oceanic carbon cycles through rivers at the global scale. Here we use ultrahigh‐resolution mass spectrometry to identify 184 molecular formulae that are indicators of riverine inputs (referred to as t‐Peaks) and to track their distribution in the deep North Atlantic and North Pacific Oceans. The t‐Peaks were found to be enriched in the Amazon River, to be highly correlated with known tracers of terrigenous input, and to be observed in all samples from four different rivers characterized by vastly different landscapes and vegetation coverage spanning equatorial (Amazon and Congo), subtropical (Altamaha), and Arctic (Kolyma) regions. Their distribution reveals that terrigenous organic matter is injected into the deep ocean by the global meridional overturning circulation, indicating that a fraction of the terrigenous DOM introduced by rivers contributes to the DOM pool observed in the deep ocean and to the storage of terrigenous organic carbon. This novel molecular approach can be used to further constrain the transfer of DOM from land to sea, especially considering that Fourier transform ion cyclotron resonance mass spectrometer analysis is becoming increasingly frequent in studies characterizing the molecular composition of DOM in lakes, rivers, and the ocean.

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Molecular-level changes of dissolved organic matter along the Amazon River-to-ocean continuum

Cited by 213 publications

References 118 publications

Microbially-Mediated Transformations of Estuarine Dissolved Organic Matter

Microbially-Mediated Transformations of Estuarine Dissolved Organic Matter

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

A novel molecular approach for tracing terrigenous dissolved organic matter into the deep ocean

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