scholarly journals Dynamics and Characterization of Refractory Dissolved Organic Matter Produced by a Pure Bacterial Culture in an Experimental Predator-Prey System

2006 ◽  
Vol 72 (6) ◽  
pp. 4184-4191 ◽  
Author(s):  
David F. Gruber ◽  
Jean-Paul Simjouw ◽  
Sybil P. Seitzinger ◽  
Gary L. Taghon
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Trophic Levels ◽  
Ionization Mass ◽  
Predator Prey ◽  
Doc Concentration ◽  
Pure Bacterial Culture ◽  
New Compounds

ABSTRACT We studied the effects of a bacterium (Pseudomonas chlororaphis) and a bactivorous protozoan (Uronema sp.) on transformations of labile dissolved organic carbon (DOC). In 36-day time series experiments, bacteria were grown on glucose both with and without protozoa. We measured bulk organic carbon pools and used electrospray ionization mass spectrometry to characterize dissolved organic matter on a molecular level. Bacteria rapidly utilized glucose, depleting it to nondetectable levels and producing new DOC compounds of higher molecular weight within 2 days. Some of these new compounds, representing 3 to 5% of the initial glucose-C, were refractory and persisted for over a month. Other new compounds were produced and subsequently used by bacteria during the lag and exponential growth phases, pointing to a dynamic cycling of organic compounds. Grazers caused a temporary spike in the DOC concentration consisting of labile compounds subsequently utilized by the bacteria. Grazing did not increase the complexity of the DOC pool already established by the bacteria but did continually decrease the particulate organic carbon pool and expedited the conversion of glucose-C to CO2. After 36 days, 29% of initial glucose-C remained in pure bacteria cultures, while only 6% remained in cultures where a grazer was present. In this study the bacteria were the primary shapers of the complex DOC continuum, suggesting higher trophic levels possibly have less of an impact on the qualitative composition of DOC than previously assumed.

scholarly journals Seasonal Changes in Dissolved Organic Matter Composition in a Patagonian Fjord Affected by Glacier Melt Inputs

2021 ◽  
Vol 8 ◽  
Author(s):  
Matthew G. Marshall ◽  
Anne M. Kellerman ◽  
Jemma L. Wadham ◽  
Jon R. Hawkings ◽  
Giovanni Daneri ◽  
...  
Keyword(s):  
Organic Matter ◽  
Surface Layer ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Relative Contribution ◽  
Glacier Melt ◽  
Level Data ◽  
Chilean Patagonia ◽  
Doc Concentration ◽  
Dom Composition

Biogeochemical processes in fjords are likely affected by changes in surrounding glacier cover but very little is known about how meltwater directly influences dissolved organic matter (DOM) in fjords. Moreover, the data available are restricted to a handful of northern hemisphere sites. Here we analyze seasonal and spatial variation in dissolved organic carbon (DOC) concentration and DOM composition (spectrofluorescence, ultrahigh resolution mass spectrometry) in Baker-Martinez Fjord, Chilean Patagonia (48°S), to infer the impacts of rapid regional deglaciation on fjord DOM. We show that surface layer DOC concentrations do not vary significantly between seasons, but DOM composition is sensitive to differences in riverine inputs. In summer, higher protein-like fluorescence reflects increased glacial meltwater inputs, whilst molecular level data show weaker influence from marine DOM due to more intense stratification. We postulate that the shifting seasonal balance of riverine and marine waters affects the supply of biolabile peptides and organic nitrogen cycling in the surface layer. Trends in DOM composition with increasing salinity are consistent with patterns in estuaries (i.e. preferential removal of aromatic compounds and increasing relative contribution of unsaturated and heteroatom-rich DOM from marine sources). Preliminary estimates also suggest that at least 10% of the annual organic carbon stock in this fjord is supplied by the four largest, glacially fed rivers and that these inputs are dominated by dissolved (84%) over particulate organic carbon. Riverine DOC may therefore be an important carbon subsidy to bacterial communities in the inner fjord. The overall findings highlight the biogeochemical sensitivity of a Patagonian fjord to changes in glacier melt input, which likely has relevance for other glaciated fjords in a warming climate.

scholarly journals The non-conservative distribution pattern of organic matter in Rajang, a tropical river with peatland in its estuary

2019 ◽  
Author(s):  
Zhuoyi Zhu ◽  
Joanne Oakes ◽  
Bradley Eyre ◽  
Youyou Hao ◽  
Edwin Sien Aun Sia ◽  
...  
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Anthropogenic Activities ◽  
Field Investigation ◽  
Organic Matter Composition ◽  
Doc Concentration ◽  
Nitrogen Ratio ◽  
Export Pattern

Abstract. South-east Asian peatland-draining rivers have attracted much attention due to their high dissolved organic carbon (DOC) yield and high CO2 emissions under anthropogenic activities. In August 2016, we carried out a field investigation of the Rajang river and estuary, a tropical system located in Sarawak, Malaysia. The Rajang has peatland in its estuary while the river basin is covered by tropical rainforest. DOC δ13C in the Rajang ranged from −28.7 ‰ to −20.1 ‰ and a U-shaped trend from river to estuary was identified. For particulate organic carbon (POC), the δ13C ranged between −29.4 ‰ to −31.1 ‰ in the river and a clear increasing trend towards more δ13C -enriched with higher salinity existed in the estuary. In the estuary, there was a linear conservative dilution pattern for dissolved organic matter composition (as quantified by D/L amino acids enantiomers) plotted against DOC δ13C, whereas when plotted against salinity dissolved D/L amino acids enantiomers values were higher than the theoretical dilution value. Together, these data indicate that the addition of DOC in estuary (by peatland) not only increased the DOC concentration, but also altered its composition, by adding more bio-degraded, 13C-depleted organic matter into the bulk dissolved organic matter. Alteration of organic matter composition (adding of more degraded subpart) was also apparent for the particulate phase, but patterns were less clear. The Rajang was characterized by DOC / DON ratios of 50 in the river section, with loss of DON in the estuary increased the ratio to 140, suggesting the unbalanced export pattern for organic carbon and nitrogen, respectively. Under anthropogenic activities, further assessment of organic carbon to nitrogen ratio is needed.

Modern methane and dissolved organic matter radiocarbon signatures suggest rapid transfer of organic carbon from a tropical forest to the underlying subterranean estuary ecosystem

2020 ◽  
Author(s):  
David Brankovits ◽  
John Pohlman ◽  
Mark Garnett ◽  
Joshua Dean
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Food Web ◽  
Land Surface ◽  
Dissolved Inorganic Carbon ◽  
Trophic Levels ◽  
Carbon Turnover ◽  
Isotopic Analyses ◽  
Subterranean Estuaries

<p>Biogeochemical processing of dissolved organic matter, including methane, along sharp salinity gradients in subterranean estuaries greatly alters the composition of submarine groundwater discharge into the marine environment. Along the margins of coastal carbonate (karst) platforms, which account for ~25% of all coastlines, subterranean estuaries extend kilometers inland within porous bedrock, flooding extensive cave networks. This environment harbors a poorly understood, but globally dispersed, anchialine fauna (invertebrates with subterranean adaptations) and characteristic microbial communities. In Mexico’s Yucatan Peninsula, microbial processing of methane and dissolved organic carbon (DOC), originating from overlying tropical soils, is the critical link for shuttling organic matter to higher trophic levels of the food web within the coastal aquifer. To better understand carbon turnover during organic matter transformations in this habitat, we collected samples for stable and radiocarbon analyses targeting the biotic and abiotic components of the carbon cycle. In the freshwater, radiocarbon signatures of terrestrially originated DOC (pMC = 105.1; [DOC] = 517 µM; δ<sup>13</sup>C = ˗27.8 ‰) and methane (pMC = 101.6; [CH<sub>4</sub>] = 6460 nM; δ<sup>13</sup>C = ˗71.5 ‰) correspond with modern <sup>14</sup>C ages, suggesting these sources of energy within the habitat are comprised of modern carbon fixed recently by photosynthesizing primary producers at the land surface. By contrast, DOC in the deeper saline groundwater is significantly lower in concentration (21 µM), and substantially older (pMC = 47.3, equates to 6010 ± 95 <sup>14</sup>C yrs). Similarly, dissolved inorganic carbon (DIC) in the freshwater is significantly younger (pMC = 86.5, equates to 1170 ± 15 <sup>14</sup>C yrs) than in the deeper saline water (pMC = 58.4, equates to 4320 ± 25 <sup>14</sup>C yrs). These findings demonstrate that important sources of nutrition for the food web are intimately linked to the overlying subaerial habitat, which suggests these ecosystems are highly vulnerable to nearby land use alterations. Furthermore, this study provides new insights into carbon turnover during the process of methane production/consumption, carbon exchange, and organic matter transformation before the emission of the dissolved constituents into coastal oceans from karst subterranean estuaries. Radiocarbon and stable isotopic analyses of the resident fauna will allow us to evaluate the ecological effects of the rapid top-down transfer mechanism for methane and DOC. Beyond better understanding the sources and fate of these carbon sources, our findings have the potential to support management and conservation efforts aimed at coastal groundwater ecosystems.</p>

scholarly journals Influence of Dissolved Organic Matter Sources on In-Stream Net Dissolved Organic Carbon Uptake in a Mediterranean Stream

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1722 ◽  
Author(s):  
Anna Lupon ◽  
Núria Catalán ◽  
Eugènia Martí ◽  
Susana Bernal
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Dissolved Organic Carbon ◽  
Leaf Litter ◽  
Natural Conditions ◽  
Mediterranean Stream ◽  
Doc Concentration ◽  
The Relationship ◽  
Different Sources

Studies exploring how different sources of dissolved organic matter (DOM) influence in-stream dissolved organic carbon (DOC) uptake at the ecosystem scale are scarce in the literature. To fill this knowledge gap, we examined the relationship between DOM sources and in-stream net DOC uptake (UDOC) in a sub-humid Mediterranean stream. We considered four reach-scale scenarios occurring under natural conditions that differed in predominant DOM sources (groundwater, leaf litter, and/or upstream water). Results showed that groundwater inputs favored in-stream net DOC uptake, while leaf litter inputs promoted in-stream net DOC release. However, there was no clear effect of DOM source mixing on the magnitude of UDOC. Further, the variability in UDOC within and among scenarios was mostly explained by stream DOC concentration, suggesting that DOC availability limits microbial activity in this stream. DOM composition became a controlling factor of UDOC variability only during the leaf litter period, when stream DOC concentration was the highest. Together, these results suggest that the capacity of headwater forested streams to process DOC is closely tied to the availability of different DOM sources and how they vary over time and along the river network.

scholarly journals Dissolved Metal(loid) Concentrations and Their Relations with Chromophoric and Fluorescent Dissolved Organic Matter in an Urban River in Shenzhen, South China

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 281 ◽  
Author(s):  
Song Zhang ◽  
Xun-Wen Chen ◽  
Quanhui Ye ◽  
Zi-Ting Zhang ◽  
Si-Fang Kong ◽  
...  
Keyword(s):  
Organic Matter ◽  
Wastewater Treatment ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Treatment Plant ◽  
National Standards ◽  
Urban Rivers ◽  
Ultraviolet Absorbance ◽  
Fluorescent Dissolved Organic Matter ◽  
Doc Concentration

Urbanization is often accompanied by aquatic metal(loid) pollution, which is regulated by dissolved organic matter (DOM). However, the relationships between dissolved metal(loid) concentration and the bulk, chromophoric, and fluorescent DOM in black and odorous urban rivers are still poorly understood. Here, we investigated the dissolved metal(loid) concentrations of Zn, Cu, Cr, As, Pb, and Cd and their correlations with DOM-related parameters in water samples from a polluted urbanized watershed in Shenzhen, China. The results showed that the Zn and Cu concentrations in the mainstream and tributary exceeded the national standards, and the wastewater treatment plant (WWTP) was an important source, as indicated by the abrupt concentration increases downstream of the WWTP. The dissolved metal(loid) concentrations were not always significantly correlated with the dissolved organic carbon (DOC) concentration or the ultraviolet absorbance at 254 nm (UV254); however, they were more likely to be correlated with the maximum fluorescence intensity (Fmax) of protein-like fluorescent DOM components. A strong correlation between the Cu/DOC ratio and specific UV254 (SUVA254) previously reported did not exist in the present study. Instead, the Cu/DOC ratio was positively correlated with the Fmax/DOC ratios for protein-like fluorescent DOM components. Our study highlights that protein-like fluorescent DOM may be more important than humic-like fluorescence DOM and chromophoric DOM in terms of interacting with dissolved metal(loid)s in black and odorous urban rivers.

scholarly journals Heterotrophic Bacterial Growth Efficiency and Community Structure at Different Natural Organic Carbon Concentrations

2003 ◽  
Vol 69 (7) ◽  
pp. 3701-3709 ◽  
Author(s):  
Alexander Eiler ◽  
Silke Langenheder ◽  
Stefan Bertilsson ◽  
Lars J. Tranvik
Keyword(s):  
Growth Rate ◽  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Community Composition ◽  
Bacterial Growth ◽  
Bacterial Biomass ◽  
Growth Efficiency ◽  
Bacterial Growth Efficiency ◽  
Doc Concentration

ABSTRACT Batch cultures of aquatic bacteria and dissolved organic matter were used to examine the impact of carbon source concentration on bacterial growth, biomass, growth efficiency, and community composition. An aged concentrate of dissolved organic matter from a humic lake was diluted with organic compound-free artificial lake water to obtain concentrations of dissolved organic carbon (DOC) ranging from 0.04 to 2.53 mM. The bacterial biomass produced in the cultures increased linearly with the DOC concentration, indicating that bacterial biomass production was limited by the supply of carbon. The bacterial growth rate in the exponential growth phase exhibited a hyperbolic response to the DOC concentration, suggesting that the maximum growth rate was constrained by the substrate concentration at low DOC concentrations. Likewise, the bacterial growth efficiency calculated from the production of biomass and CO2 increased asymptotically from 0.4 to 10.4% with increasing DOC concentration. The compositions of the microbial communities that emerged in the cultures were assessed by separation of PCR-amplified 16S rRNA fragments by denaturing gradient gel electrophoresis. Nonmetric multidimensional scaling of the gel profiles showed that there was a gradual change in the community composition along the DOC gradient; members of the β subclass of the class Proteobacteria and members of the Cytophaga-Flavobacterium group were well represented at all concentrations, whereas members of the α subclass of the Proteobacteria were found exclusively at the lowest carbon concentration. The shift in community composition along the DOC gradient was similar to the patterns of growth efficiency and growth rate. The results suggest that the bacterial growth efficiencies, the rates of bacterial growth, and the compositions of bacterial communities are not constrained by substrate concentrations in most natural waters, with the possible exception of the most oligotrophic environments.

scholarly journals The nonconservative distribution pattern of organic matter in the Rajang, a tropical river with peatland in its estuary

2020 ◽  
Vol 17 (9) ◽  
pp. 2473-2485
Author(s):  
Zhuo-Yi Zhu ◽  
Joanne Oakes ◽  
Bradley Eyre ◽  
Youyou Hao ◽  
Edwin Sien Aun Sia ◽  
...  
Keyword(s):  
Organic Matter ◽  
Amino Acid ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Anthropogenic Activities ◽  
Field Investigation ◽  
Carbon And Nitrogen ◽  
Organic Matter Composition ◽  
Doc Concentration ◽  
Amino Acid Enantiomer

Abstract. Southeast Asian peatland-draining rivers have attracted much attention due to their high dissolved organic carbon (DOC) yield and high CO2 emissions under anthropogenic influences. In August 2016, we carried out a field investigation of the Rajang River and its estuary, a tropical system located in Sarawak, Malaysia. The Rajang has peatland in its estuary, while the river basin is covered by tropical rainforest. DOC-δ13C in the Rajang ranged from −28.7 ‰ to −20.1 ‰, with a U-shaped trend from river to estuary. For particulate organic carbon (POC), δ13C ranged between −29.4 ‰ and −31.1 ‰ in the river, and there was a clear increasing trend towards more enriched δ13C values with higher salinity. In the estuary, there was a linear conservative dilution pattern for dissolved organic matter composition (as quantified by D- and L-amino acid enantiomers) plotted against DOC-δ13C, whereas when plotted against salinity, dissolved D- and L-amino acid enantiomer values were higher than the theoretical dilution value. Together, these data indicate that the addition of DOC to the estuary (by peatland) not only increased the DOC concentration but also altered its composition, by adding more biodegraded, 13C-depleted organic matter into the bulk dissolved organic matter. Alteration of organic matter composition (addition of a more degraded subpart) was also apparent for the particulate phase, but patterns were less clear. The Rajang was characterized by DOC to DON (dissolved organic nitrogen) ratios of 50 in the river section, with loss of DON in the estuary increasing the ratio to 140, suggesting an unbalanced export of organic carbon and nitrogen. Where affected by anthropogenic activities, further assessment of organic carbon to nitrogen ratios is needed.

Sign in / Sign up

Export Citation Format

Share Document