scholarly journals Hydrology controls dissolved organic matter export and composition in an Alpine stream and its hyporheic zone

2015 ◽  
Vol 61 (2) ◽  
pp. 558-571 ◽  
Author(s):  
Christina Fasching ◽  
Amber J. Ulseth ◽  
Jakob Schelker ◽  
Gertraud Steniczka ◽  
Tom J. Battin
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Hyporheic Zone ◽  
Alpine Stream

scholarly journals Spatiotemporal transformation of dissolved organic matter along an alpine stream flow path on the Qinghai–Tibet Plateau: importance of source and permafrost degradation

2018 ◽  
Vol 15 (21) ◽  
pp. 6637-6648 ◽  
Author(s):  
Yinghui Wang ◽  
Robert G. M. Spencer ◽  
David C. Podgorski ◽  
Anne M. Kellerman ◽  
Harunur Rashid ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Molecular Level ◽  
Tibet Plateau ◽  
Permafrost Degradation ◽  
Hydrological Conditions ◽  
14C Age ◽  
Alpine Stream ◽  
Qinghai Tibet Plateau

Abstract. The Qinghai–Tibet Plateau (QTP) accounts for approximately 70 % of global alpine permafrost and is an area sensitive to climate change. The thawing and mobilization of ice-rich and organic-carbon-rich permafrost impact hydrologic conditions and biogeochemical processes on the QTP. Despite numerous studies of Arctic permafrost, there are no reports to date for the molecular-level in-stream processing of permafrost-derived dissolved organic matter (DOM) on the QTP. In this study, we examine temporal and spatial changes of DOM along an alpine stream (3850–3207 m above sea level) by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), accelerator mass spectrometry (AMS) and UV–visible spectroscopy. Compared to downstream sites, dissolved organic matter (DOM) at the headstream site exhibited older radiocarbon age, higher mean molecular weight, higher aromaticity and fewer highly unsaturated compounds. At the molecular level, 6409 and 1345 formulas were identified as unique to the active layer (AL) leachate and permafrost layer (PL) leachate, respectively. Comparing permafrost leachates to the downstream site, 59 % of AL-specific formulas and 90 % of PL-specific formulas were degraded, likely a result of rapid in-stream degradation of permafrost-derived DOM. From peak discharge in the summer to low flow in late autumn, the DOC concentration at the headstream site decreased from 13.9 to 10.2 mg L−1, while the 14C age increased from 745 to 1560 years before present (BP), reflecting an increase in the relative contribution of deep permafrost carbon due to the effect of changing hydrological conditions over the course of the summer on the DOM source (AL vs. PL). Our study thus demonstrates that hydrological conditions impact the mobilization of permafrost carbon in an alpine fluvial network, the signature of which is quickly lost through in-stream mineralization and transformation.

scholarly journals Functional and Structural Responses of Hyporheic Biofilms to Varying Sources of Dissolved Organic Matter

2014 ◽  
Vol 80 (19) ◽  
pp. 6004-6012 ◽  
Author(s):  
Karoline Wagner ◽  
Mia M. Bengtsson ◽  
Katharina Besemer ◽  
Anna Sieczko ◽  
Nancy R. Burns ◽  
...  
Keyword(s):  
Organic Matter ◽  
16S Rrna ◽  
Dissolved Organic Matter ◽  
Community Composition ◽  
Hyporheic Zone ◽  
Priority Effects ◽  
Stream Ecosystems ◽  
Rrna Gene ◽  
Structural Responses

ABSTRACTHeadwater streams are tightly connected with the terrestrial milieu from which they receive deliveries of organic matter, often through the hyporheic zone, the transition between groundwater and streamwater. Dissolved organic matter (DOM) from terrestrial sources (that is, allochthonous) enters the hyporheic zone, where it may mix with DOM fromin situproduction (that is, autochthonous) and where most of the microbial activity takes place. Allochthonous DOM is typically considered resistant to microbial metabolism compared to autochthonous DOM. The composition and functioning of microbial biofilm communities in the hyporheic zone may therefore be controlled by the relative availability of allochthonous and autochthonous DOM, which can have implications for organic matter processing in stream ecosystems. Experimenting with hyporheic biofilms exposed to model allochthonous and autochthonous DOM and using 454 pyrosequencing of the 16S rRNA (targeting the “active” community composition) and of the 16S rRNA gene (targeting the “bulk” community composition), we found that allochthonous DOM may drive shifts in community composition whereas autochthonous DOM seems to affect community composition only transiently. Our results suggest that priority effects based on resource-driven stochasticity shape the community composition in the hyporheic zone. Furthermore, measurements of extracellular enzymatic activities suggest that the additions of allochthonous and autochthonous DOM had no clear effect on the function of the hyporheic biofilms, indicative of functional redundancy. Our findings unravel possible microbial mechanisms that underlie the buffering capacity of the hyporheic zone and that may confer stability to stream ecosystems.

scholarly journals Spatiotemporal transformation of dissolved organic matter along an alpine stream flowpath on the Qinghai-Tibetan Plateau: importance of source and permafrost degradation

2018 ◽  
Author(s):  
Yinghui Wang ◽  
Robert G. M. Spencer ◽  
David Podgorski ◽  
Anne Kellerman ◽  
Harunur Rashid ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Organic Matter ◽  
Tibetan Plateau ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Molecular Level ◽  
Permafrost Degradation ◽  
Hydrological Conditions ◽  
14C Age ◽  
Alpine Stream

Abstract. The Qinghai-Tibetan Plateau (QTP) accounts for approximately 70 % of global alpine permafrost and is an area sensitive to climate change. The thawing and mobilization of ice and organic carbon-rich permafrost impact hydrologic conditions and biogeochemical processes on the QTP. Despite numerous studies of Arctic permafrost, there are no reports to date for the molecular-level in-stream processing of permafrost-derived dissolved organic matter (DOM) on the QTP. In this study, we examine temporal and spatial changes of chemical composition of DOM and 14C age of dissolved organic carbon (DOC) along an alpine stream (3850–3207 m above sea level) by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), accelerator mass spectrometry (AMS) and UV-visible spectroscopy. Compared to downstream sites, the DOM at the headstream exhibited older radiocarbon (14C-DOC) age, higher mean molecular weight, higher aromaticity and fewer polyunsaturated components. At the molecular level, 6409 and 1345 formulas were identified as unique to the active layer (AL) leachate and permafrost layer (PL) leachate, respectively. Comparing permafrost leachates to the downstream site, 59 % of AL-specific formulas and 90 % of PL-specific formulas were degraded, likely a result of rapid instream degradation of permafrost-derived DOM. From peak discharge in the summer to low flow in late autumn, the DOC concentration at the headstream site decreased from 13.9 to 10.2 mg/L, while the 14C-DOC age increased from 745 to 1560 years before present (BP), reflecting an increase in relative contribution of deep permafrost carbon due to the effect of changing hydrological conditions over the course of the summer on DOM source (AL vs. PL). Our study thus demonstrates that hydrological conditions impact the mobilization of permafrost carbon in an alpine fluvial network, the signature of which is quickly lost through in-stream metabolism.

scholarly journals Coupled Biotic-Abiotic Processes Control Biogeochemical Cycling of Dissolved Organic Matter in the Columbia River Hyporheic Zone

2021 ◽  
Vol 2 ◽  
Author(s):  
Jane D. Fudyma ◽  
Rosalie K. Chu ◽  
Nathalia Graf Grachet ◽  
James C. Stegen ◽  
Malak M. Tfaily
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Ground Water ◽  
River Water ◽  
Microbial Activity ◽  
Hyporheic Zone ◽  
Light Exposure ◽  
Abiotic Factors ◽  
Columbia River ◽  
Transformation Pathways

A critical component of assessing the impacts of climate change on watershed ecosystems involves understanding the role that dissolved organic matter (DOM) plays in driving whole ecosystem metabolism. The hyporheic zone—a biogeochemical control point where ground water and river water mix—is characterized by high DOM turnover and microbial activity and is responsible for a large fraction of lotic respiration. Yet, the dynamic nature of this ecotone provides a challenging but important environment to parse out different DOM influences on watershed function and net carbon and nutrient fluxes. We used high-resolution Fourier-transform ion cyclotron resonance mass spectrometry to provide a detailed molecular characterization of DOM and its transformation pathways in the Columbia river watershed. Samples were collected from ground water (adjacent unconfined aquifer underlying the Hanford 300 Area), Columbia river water, and its hyporheic zone. The hyporheic zone was sampled at five locations to capture spatial heterogeneity within the hyporheic zone. Our results revealed that abiotic transformation pathways (e.g., carboxylation), potentially driven by abiotic factors such as sunlight, in both the ground water and river water are likely influencing DOM availability to the hyporheic zone, which could then be coupled with biotic processes for enhanced microbial activity. The ground water profile revealed high rates of N and S transformations via abiotic reactions. The river profile showed enhanced abiotic photodegradation of lignin-like molecules that subsequently entered the hyporheic zone as low molecular weight, more degraded compounds. While the compounds in river water were in part bio-unavailable, some were further shown to increase rates of microbial respiration. Together, river water and ground water enhance microbial activity within the hyporheic zone, regardless of river stage, as shown by elevated putative amino-acid transformations and the abundance of amino-sugar and protein-like compounds. This enhanced microbial activity is further dependent on the composition of ground water and river water inputs. Our results further suggest that abiotic controls on DOM should be incorporated into predictive modeling for understanding watershed dynamics, especially as climate variability and land use could affect light exposure and changes to ground water essential elements, both shown to impact the Columbia river hyporheic zone.

Dissolved organic matter transformation in the hyporheic zone of a small lowland river

2010 ◽  
Vol 39 (2) ◽  
Author(s):  
Piotr Zieliński ◽  
Elżbieta Jekatierynczuk-Rudczyk
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Hyporheic Zone ◽  
Stream Water ◽  
Small Scale ◽  
Lowland River ◽  
Organic Matter Transformation ◽  
Doc Concentration ◽  
Different Depths ◽  
Study Sites

Dissolved organic matter transformation in the hyporheic zone of a small lowland riverThe objective of this study was to examine dissolved organic carbon (DOC) concentration and specific ultraviolet absorbance (SUVA) changes in porewaters that occur over a small scale (cm) in the hyporheic zone (HZ) of a lowland stream in the Knyszynska Forest in northeast Poland. Hyporheic zone porewaters were sampled at different depths of 10, 30, 50, 70 cm at two study sites with different sediment material. The results showed significant differences in DOC concentrations between the upper and lower stream HZ. The current results indicate that small lowland sediments provide both a source and a sink of DOC for stream water, depending on the river course. The higher DOC level observed in the hyporheic zone suggests that porewater can be an autonomic site of biogeochemical changes of dissolved organic matter, which is very clear in the SUVA fluctuations.

Travel time and source variation explain the molecular transformation of dissolved organic matter in an Alpine stream network

2020 ◽  
Author(s):  
Hannes Peter ◽  
Gabriel Andreas Singer ◽  
Amber J. Ulseth ◽  
Thorsten Dittmar ◽  
Yves T. Prairie ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Travel Time ◽  
Stream Network ◽  
Alpine Stream ◽  
Source Variation
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