Degradation of terrestrially derived macromolecules in the Amazon River

Ward, Nicholas D.; Keil, Richard G.; Medeiros, Patricia M.; Brito, Daímio Chaves; Cunha, Alan Cavalcanti da; Dittmar, Thorsten; Yager, Patricia L.; Krusche, Alex V.; Richey, Jeffrey E.

doi:10.1038/ngeo1817

Cited by 338 publications

(367 citation statements)

References 29 publications

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“…The S 275-295 values in groundwater were significantly higher than those in surface waters (Shen et al Data are reported as the average ± standard deviation Biogeochemistry (2015) 122:61-78 73 2012b; this study), indicating the average molecular weight of DOM in groundwater is lower than that in surface water (Helms et al 2008). Microbial degradation and sorption onto minerals in the unsaturated zone are likely responsible for the removal of lignin and other components of chromophoric DOM (Kaiser et al 2004;Inamdar et al 2011;Ward et al 2013).…”

Section: Discussionmentioning

confidence: 99%

Origins and bioavailability of dissolved organic matter in groundwater

et al. 2014

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Dissolved organic matter (DOM) in groundwater influences water quality and fuels microbial metabolism, but its origins, bioavailability and chemical composition are poorly understood. The origins and concentrations of dissolved organic carbon (DOC) and bioavailable DOM were monitored during a long-term (2-year) study of groundwater in a fractured-rock aquifer in the Carolina slate belt. Surface precipitation was significantly correlated with groundwater concentrations of DOC, bioavailable DOM and chromophoric DOM, indicating strong hydrological connections between surface and ground waters. The physicochemical and biological processes shaping the concentrations and compositions of DOM during its passage through the soil column to the saturated zone are conceptualized in the regional chromatography model. The model provides a framework for linking hydrology with the processes affecting the transformation, remineralization and microbial production of DOM during passage through the soil column. Lignin-derived phenols were relatively depleted in groundwater DOM indicating substantial removal in the unsaturated zone, and optical properties of chromophoric DOM indicated lower molecular weight DOM in groundwater relative to surface water. The prevalence of glycine, caminobutyric acid, and D-enantiomers of amino acids indicated the DOM was highly diagenetically altered. Bioassay experiments were used to establish DOCnormalized yields of amino acids as molecular indicators of DOM bioavailability in groundwater. A relatively small fraction (8 ± 4 %) of DOC in groundwater was bioavailable. The relatively high yields of specific D-enantiomers of amino acids indicated a substantial fraction (15-34 %) of groundwater DOC was of bacterial origin.

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Section: Discussionmentioning

confidence: 99%

Origins and bioavailability of dissolved organic matter in groundwater

et al. 2014

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“…It has long been recognized that terrestrial DOC is susceptible to photochemical degradation in the water 23 , but it has traditionally been assumed that this DOC is generally recalcitrant to biological degradation [24][25][26] , and therefore that the contribution of this latter pathway to aquatic CO 2 production is modest. This view is rapidly changing 24,25 , and a growing volume of evidence indicates that terrestrial DOC may be readily degraded by biological processes in aquatic environments, such as the Amazon basin 27 and the Arctic 8,28 , temperate 29,30 and boreal 31,32 biomes. Boreal biomes contain the highest density of freshwater on Earth, yet this evidence for biologically degradable DOC is scattered and based on isolated components of the continental aquatic network.…”

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confidence: 99%

Increases in terrestrially derived carbon stimulate organic carbon processing and CO2 emissions in boreal aquatic ecosystems

et al. 2013

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“…An even smaller fraction of total primary productivity, <0.5% Burdige, 2007), equivalent to 0.1-0.2 Gt/yr, reaches the seafloor sediment surface . These fluxes into the deep ocean are small, owing to rapid heterotrophic remineralization and photo-oxidation in the water column and within rivers Amon and Benner, 1996;Benner and Biddanda, 1998;Mayorga et al, 2005;Ward et al, 2013;, but they remove carbon from the atmosphere for centuries to millennia. Over these long time scales, this deep reservoir amasses several orders of magnitude more carbon than do the terrestrial and marine primary producer reservoirs.…”

Section: The Modern Carbon Cyclementioning

confidence: 99%

Novel analytical strategies for tracing the organic carbon cycle in marine and riverine particles

Rosengard¹

2017

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Particulate organic carbon (POC) in the ocean and mobilized by rivers on land transfers ~0.1% of global primary productivity to the deep ocean sediments. This small fraction regulates the long-term carbon cycle by removing carbon dioxide from the atmosphere for centuries to millennia. This thesis investigates mechanisms of POC transfer to the deep ocean by analyzing particles collected in transit through two globally significant carbon reservoirs: the Southern Ocean and the Amazon River Basin. These endeavors test the hypothesis that organic matter composition controls the recycling and transfer efficiency of POC to the deep ocean, and illustrate new applications for ramped pyrolysis/oxidation (RPO), a growing method of POC characterization by thermal stability. By coupling RPO to stable and radiocarbon isotope analyses of riverine POC, I quantify three thermally distinct soil organic carbon pools mobilized by the Amazon River, and evaluate the degradability and fate of these different pools during transport to the coastal Atlantic Ocean. More directly, RPO analyses of marine samples suggest that POC transfer in the water column is in fact selective. Observations of consistent biomolecular changes that accompany transport of phytoplankton-derived organic matter to depth across the Southern Ocean support the argument for preferential degradation of specific POC pools in the water column. Combining discussions of POC recycling and transfer across both marine and terrestrial systems offer new perspectives of thermal stability as a proxy for diagenetic stability and POC degradation state. The challenges of interpreting RPO data in these two environments set the stage for applying the technique to more controlled experiments that trace POC from source to long-term sink.

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Degradation of terrestrially derived macromolecules in the Amazon River

Cited by 338 publications

References 29 publications

Origins and bioavailability of dissolved organic matter in groundwater

Origins and bioavailability of dissolved organic matter in groundwater

Increases in terrestrially derived carbon stimulate organic carbon processing and CO2 emissions in boreal aquatic ecosystems

Novel analytical strategies for tracing the organic carbon cycle in marine and riverine particles

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