Spatial Variation in the Molecular Composition of Dissolved Organic Matter from the Podzol Soils of a Temperate Pine Forest

<p>With surface systems changing rapidly on a global scale, it is important to understand how this will affect groundwater resources and ecosystems in the subsurface. The molecular composition of dissolved organic matter (DOM) integrates essential information on metabolic functioning and could therefore reveal changes of groundwater ecosystems in high detail. Here, we evaluate a 6-year time series of ultrahigh-resolution DOM composition analysis of groundwater from a hillslope well transect within the Hainich Critical Zone Exploratory, Germany. We predict ecosystem functionality by assigning molecular sum formulas to metabolic pathways via the KEGG database. Our data support hydrogeological characterizations of a compartmentalized fractured multi-storey aquifer system and reveal distinct metabolic functions that largely depend on the compartment&#8217;s relative surface-connectivity or isolation. We show that seasonal fluctuation of groundwater levels, coinciding with cross-stratal exchange can substantially impact the local inventory of functional metabolites in DOM. Furthermore, we find that extreme conditions of groundwater recharge following pronounced groundwater lowstand cause strong alterations of the functional metabolome in DOM even in aquifer compartments, which usually show minimal variation in DOM composition. Our findings suggest that bedrock groundwater ecosystems might be functionally vulnerable to hydrogeological extremes.</p>

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Antioxidant Activity and Phenolic Content of Marine Dissolved Organic Matter and Their Relation to Molecular Composition

Frontiers in Marine Science ◽

10.3389/fmars.2020.603447 ◽

2020 ◽

Vol 7 ◽

Author(s):

Teresa S. Catalá ◽

Pamela E. Rossel ◽

Félix Álvarez-Gómez ◽

Jan Tebben ◽

Félix L. Figueroa ◽

...

Keyword(s):

Antioxidant Activity ◽

Organic Matter ◽

Free Radical ◽

Pacific Ocean ◽

Dissolved Organic Matter ◽

North Pacific ◽

Phenolic Content ◽

North Pacific Ocean ◽

Molecular Composition ◽

Antioxidant Potential

The potential of marine dissolved organic matter (DOM) for free radical scavenging has been extensively evaluated, however, the quantitative assessment of the antioxidant potential has been recently measured for the first time. The linkage of the DOM antioxidant potential to its molecular composition has not yet been examined. Following this line, this article takes a step forward by assessing, throughout a polarity-mediated fractionation, (1) the antioxidant capacity and phenolic content and (2) the molecular characterization of DOM in a more exhaustive manner. (3) The DOM antioxidant potential and phenolic content was linked to the molecular composition of DOM, which was molecularly characterized using ultrahigh resolution Fourier transform Ion Cyclotron Resonance mass spectrometry (FT-ICR MS). Antioxidant activity and phenolic content were quantified by the free radical 2,2’-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS⋅) and the Folin-Ciocalteu methods, respectively. We considered three types of different natural DOM samples: the deep North Pacific Ocean, the oligotrophic surface of the North Pacific Ocean and porewater from the sulfidic tidal flats of the Wadden Sea. Bulk porewater and its individual polarity fractions presented the highest antioxidant activity and phenolic content. DOM from the water column samples had lower antioxidant activity and phenolic content than porewater, but exceeded what it is commonly found in macroalgae, microalgae, fruits and vegetables with cosmeceutical purposes. Our values were similar to published values for terrestrial DOM. The variations in bioactivity were dependent on polarity and molecular composition. The high resolution and high mass accuracy used to determine the molecular composition of marine DOM and the chemometric and multistatistical analyses employed have allowed to distinguish molecular categories that are related to the bioactive potential. As a future perspective, we performed cytotoxicity tests with human cells and propose marine DOM as a natural ingredient for the development of cosmeceutical products.

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Linking the molecular composition of autochthonous dissolved organic matter to source identification for freshwater lake ecosystems by combination of optical spectroscopy and FT-ICR-MS analysis

The Science of The Total Environment ◽

10.1016/j.scitotenv.2019.134764 ◽

2020 ◽

Vol 703 ◽

pp. 134764 ◽

Cited By ~ 10

Author(s):

Shasha Liu ◽

Zhongqi He ◽

Zhi Tang ◽

Leizhen Liu ◽

Junwen Hou ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Optical Spectroscopy ◽

Source Identification ◽

Freshwater Lake ◽

Molecular Composition ◽

Lake Ecosystems ◽

Ms Analysis ◽

Ft Icr Ms ◽

Ft Icr

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Quality of Dissolved Organic Matter Driven by Autotrophic and Heterotrophic Microbial Processes in a Large River

Water ◽

10.3390/w12061577 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1577

Author(s):

Norbert Kamjunke ◽

Oliver J. Lechtenfeld ◽

Peter Herzsprung

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Chlorophyll A ◽

Microbial Processes ◽

Molecular Composition ◽

Longitudinal Change ◽

Mass Spectrometry Analysis ◽

High Hydrogen ◽

Chlorophyll A Concentration ◽

River Stretch

Rivers are regarded as important sites for processing of dissolved organic matter (DOM) from terrestrial sources on its way to the ocean. However, little is known about the longitudinal change of DOM molecular composition in large rivers. Here we performed a Lagrangian sampling in the lower part of the Middle Elbe at low discharge conditions to test how DOM composition changes along the river stretch and how this is related to microbial processes. The concentration of dissolved organic carbon and fluorescence indices showed only subtle longitudinal differences. In contrast, ultra-high-resolution mass spectrometry analysis of riverine DOM detected pronounced changes in molecular composition. Also, chlorophyll a concentration, bacterial abundance, and bacterial production all increased downstream. The three microbial parameters were positively related to intensities of CHO and CHNO molecular formulas with high hydrogen/carbon and low oxygen/carbon ratios but negatively to several CHOS surfactants. To disentangle the role of autotrophic and heterotrophic processes, we developed a new approach and compared slopes from linear regression of DOM compound intensities versus chlorophyll a concentration and bacteria abundance. As a result, most of the positive related DOM compounds were produced by bacteria. In conclusion, longitudinal changes of river DOM seemed to be largely driven by microbial processes.

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