Untargeted Exometabolomics Provides a Powerful Approach to Investigate Biogeochemical Hotspots with Vegetation and Polygon Type in Arctic Tundra Soils

Rising temperatures in the Arctic have led to the thawing of tundra soils, which is rapidly changing terrain, hydrology, and plant and microbial communities, causing hotspots of biogeochemical activity across the landscape. Despite this, little is known about how nutrient-rich low molecular weight dissolved organic matter (LMW DOM) varies within and across tundra ecosystems. Using a high-resolution nano-liquid chromatography-mass spectrometry (LC/MS) approach, we characterized the composition and availability of LMW DOM from high-centered polygons (HCP) and low-centered polygons (LCP) with Eriophorum angustifolium or Carex aquatilis as the dominant vegetation. Over 3000 unique features (i.e., discrete mass/charge ions) were detected; 521 were identified as differentially abundant between polygonal types and 217 were putatively annotated using high mass accuracy MS data. While polygon type was a strong predictor of LMW DOM composition and availability, vegetation and soil depth were also important drivers. Extensive evidence was found for enhanced microbial processing at the LCP sites, which were dominated by Carex plant species. We detected significant differences between polygon types with varying aboveground landscape features or properties, and hotspots of biogeochemical activity, indicating LMW DOM, as quantified by untargeted exometabolomics, provides a window into the dynamic complex interactions between landscape topography, vegetation, and organic matter cycling in Arctic polygonal tundra soils.

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Carbon degradation in Subarctic organic permafrost (peat plateaus) after thawing – what constraints CO2 and CH4 production?

10.5194/egusphere-egu21-11121 ◽

2021 ◽

Author(s):

Sigrid Trier Kjær ◽

Nora Nedkvitne ◽

Sebastian Westermann ◽

Inge Althuizen ◽

Peter Dörsch

Keyword(s):

Organic Matter ◽

Active Layer ◽

Degradation Kinetics ◽

Soil Depth ◽

The Arctic ◽

Permafrost Degradation ◽

Northern Norway ◽

Degradation Rates ◽

Peat Plateaus ◽

Carbon Degradation

Rapid warming in Subarctic areas releases large amounts of frozen carbon which can potentially result in large CO2 and CH4 emissions to the atmosphere. In Northern Norway vast amount of carbon are stored in peat plateaus, but these landscape elements have been found to decrease laterally since at least the 1950s. Peat plateaus are very sensitive to climate change as the permafrost is relatively warm compared to permafrost found in the arctic. So far, only limited information is available about potential degradation kinetics of organic carbon in these ecosystems. We sampled organic matter from depth profiles along a well-documented chronosequence of permafrost degradation in Northern Norway. After thawing over-night, we incubated permafrost and active layer for up to 3 months at 10&#176;C. To determine factors constraining degradation, we measured gas kinetics (O2, CO2, CH4) under different conditions (oxic/anoxic, loosely packed/stirred suspensions in water, with altered DOC content and nutrient amendments) and related them to pH, DOC, element (C, N, P, S) and &#948;13C and &#948;15N signatures of the peat. Organic matter degradation was strongly inhibited in the absence of oxygen. By contrast, CH4 production or release seemed to be related to soil depth rather than incubation conditions and was found to be highest in samples from the transition zone between active layer and permafrost. Degradation rates and their dependencies on peat characteristics will be compared with permafrost characteristics along the chronosequence and additional experiments exploring the role of O2, DOC and other nutrients for carbon degradation will be discussed.

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The Soil Organic Matter in Connection with Soil Properties and Soil Inputs

Agronomy ◽

10.3390/agronomy11040779 ◽

2021 ◽

Vol 11 (4) ◽

pp. 779

Author(s):

Václav Voltr ◽

Ladislav Menšík ◽

Lukáš Hlisnikovský ◽

Martin Hruška ◽

Eduard Pokorný ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Soil Texture ◽

Management Practices ◽

Soil Depth ◽

Operating Conditions ◽

Hot Water ◽

Natural Soil ◽

Soil Productivity ◽

Linear Regression Models

The content of organic matter in the soil, its labile (hot water extractable carbon–HWEC) and stable (soil organic carbon–SOC) form is a fundamental factor affecting soil productivity and health. The current research in soil organic matter (SOM) is focused on individual fragmented approaches and comprehensive evaluation of HWEC and SOC changes. The present state of the soil together with soil’s management practices are usually monitoring today but there has not been any common model for both that has been published. Our approach should help to assess the changes in HWEC and SOC content depending on the physico-chemical properties and soil´s management practices (e.g., digestate application, livestock and mineral fertilisers, post-harvest residues, etc.). The one- and multidimensional linear regressions were used. Data were obtained from the various soil´s climatic conditions (68 localities) of the Czech Republic. The Czech farms in operating conditions were observed during the period 2008–2018. The obtained results of ll monitored experimental sites showed increasing in the SOC content, while the HWEC content has decreased. Furthermore, a decline in pH and soil´s saturation was documented by regression modelling. Mainly digestate application was responsible for this negative consequence across all soils in studied climatic regions. The multivariate linear regression models (MLR) also showed that HWEC content is significantly affected by natural soil fertility (soil type), phosphorus content (−30%), digestate application (+29%), saturation of the soil sorption complex (SEBCT, 21%) and the dose of total nitrogen (N) applied into the soil (−20%). Here we report that the labile forms (HWEC) are affected by the application of digestate (15%), the soil saturation (37%), the application of mineral potassium (−7%), soil pH (−14%) and the overall condition of the soil (−27%). The stable components (SOM) are affected by the content of HWEC (17%), soil texture 0.01–0.001mm (10%), and input of organic matter and nutrients from animal production (10%). Results also showed that the mineral fertilization has a negative effect (−14%), together with the soil depth (−11%), and the soil texture 0.25–2 mm (−21%) on SOM. Using modern statistical procedures (MRLs) it was confirmed that SOM plays an important role in maintaining resp. improving soil physical, biochemical and biological properties, which is particularly important to ensure the productivity of agroecosystems (soil quality and health) and to future food security.

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DOM degradation by light and microbes along the Yukon River-coastal ocean continuum

Scientific Reports ◽

10.1038/s41598-021-89327-9 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Brice K. Grunert ◽

Maria Tzortziou ◽

Patrick Neale ◽

Alana Menendez ◽

Peter Hernes

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Salinity Gradient ◽

Coastal Ocean ◽

Interactive Effects ◽

The Arctic ◽

Yukon River ◽

Spring Freshet ◽

Dom Composition

AbstractThe Arctic is experiencing rapid warming, resulting in fundamental shifts in hydrologic connectivity and carbon cycling. Dissolved organic matter (DOM) is a significant component of the Arctic and global carbon cycle, and significant perturbations to DOM cycling are expected with Arctic warming. The impact of photochemical and microbial degradation, and their interactive effects, on DOM composition and remineralization have been documented in Arctic soils and rivers. However, the role of microbes, sunlight and their interactions on Arctic DOM alteration and remineralization in the coastal ocean has not been considered, particularly during the spring freshet when DOM loads are high, photoexposure can be quite limited and residence time within river networks is low. Here, we collected DOM samples along a salinity gradient in the Yukon River delta, plume and coastal ocean during peak river discharge immediately after spring freshet and explored the role of UV exposure, microbial transformations and interactive effects on DOM quantity and composition. Our results show: (1) photochemical alteration of DOM significantly shifts processing pathways of terrestrial DOM, including increasing relative humification of DOM by microbes by > 10%; (2) microbes produce humic-like material that is not optically distinguishable from terrestrial humics; and (3) size-fractionation of the microbial community indicates a size-dependent role for DOM remineralization and humification of DOM observed through modeled PARAFAC components of fluorescent DOM, either through direct or community effects. Field observations indicate apparent conservative mixing along the salinity gradient; however, changing photochemical and microbial alteration of DOM with increasing salinity indicate changing DOM composition likely due to microbial activity. Finally, our findings show potential for rapid transformation of DOM in the coastal ocean from photochemical and microbial alteration, with microbes responsible for the majority of dissolved organic matter remineralization.

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Spectral Characterization of Dissolved Organic Matter in Seawater and Sediment Pore Water from the Arctic Fjords (West Svalbard) in Summer

Water ◽

10.3390/w13020202 ◽

2021 ◽

Vol 13 (2) ◽

pp. 202

Author(s):

Meilian Chen ◽

Ji-Hoon Kim ◽

Sungwook Hong ◽

Yun Kyung Lee ◽

Moo Hee Kang ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Pore Water ◽

Phytoplankton Bloom ◽

Ocean Surface ◽

The Arctic ◽

Sediment Pore Water ◽

Ice Edge ◽

Accumulation Trend ◽

Arctic Fjords

Fjords in the high Arctic, as aquatic critical zones at the interface of land-ocean continuum, are undergoing rapid changes due to glacier retreat and climate warming. Yet, little is known about the biogeochemical processes in the Arctic fjords. We measured the nutrients and the optical properties of dissolved organic matter (DOM) in both seawater and sediment pore water, along with the remote sensing data of the ocean surface, from three West Svalbard fjords. A cross-fjord comparison of fluorescence fingerprints together with downcore trends of salinity, Cl−, and PO43− revealed higher impact of terrestrial inputs (fluorescence index: ~1.2–1.5 in seawaters) and glaciofluvial runoffs (salinity: ~31.4 ± 2.4 psu in pore waters) to the southern fjord of Hornsund as compared to the northern fjords of Isfjorden and Van Mijenfjorden, tallying with heavier annual runoff to the southern fjord of Hornsund. Extremely high levels of protein-like fluorescence (up to ~4.5 RU) were observed at the partially sea ice-covered fjords in summer, in line with near-ubiquity ice-edge blooms observed in the Arctic. The results reflect an ongoing or post-phytoplankton bloom, which is also supported by the higher levels of chlorophyll a fluorescence at the ocean surface, the very high apparent oxygen utilization through the water column, and the nutrient drawdown at the ocean surface. Meanwhile, a characteristic elongated fluorescence fingerprint was observed in the fjords, presumably produced by ice-edge blooms in the Arctic ecosystems. Furthermore, alkalinity and the humic-like peaks showed a general downcore accumulation trend, which implies the production of humic-like DOM via a biological pathway also in the glaciomarine sediments from the Arctic fjords.

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Bacteriohopanepolyol biomarker composition of organic matter exported to the Arctic Ocean by seven of the major Arctic rivers

Organic Geochemistry ◽

10.1016/j.orggeochem.2009.07.014 ◽

2009 ◽

Vol 40 (11) ◽

pp. 1151-1159 ◽

Cited By ~ 31

Author(s):

Martin P. Cooke ◽

Bart E. van Dongen ◽

Helen M. Talbot ◽

Igor Semiletov ◽

Natalia Shakhova ◽

...

Keyword(s):

Organic Matter ◽

Arctic Ocean ◽

The Arctic ◽

The Arctic Ocean ◽

Arctic Rivers

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Elemental and biochemical composition of organic matter in the waters of the Russian sector of the Arctic Basin under the present conditions

Oceanology ◽

10.1134/s0001437011030015 ◽

2011 ◽

Vol 51 (3) ◽

pp. 424-433

Author(s):

A. I. Agatova ◽

N. M. Lapina ◽

N. I. Torgunova

Keyword(s):

Organic Matter ◽

Biochemical Composition ◽

Arctic Basin ◽

The Arctic ◽

Russian Sector

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Field mobility of flumetsulam in three Mississippi soils

Weed Science ◽

10.1017/s0043174500088822 ◽

1997 ◽

Vol 45 (4) ◽

pp. 564-567 ◽

Cited By ~ 10

Author(s):

Glen P. Murphy ◽

David R. Shaw

Keyword(s):

Organic Matter ◽

Soil Type ◽

Soil Depth ◽

Organic Matter Content ◽

Matter Content ◽

Constant Ph ◽

Field Mobility

Research was conducted in 1994 and 1995 to evaluate the field mobility of flumetsulam in three soils of varied texture and organic matter content but constant pH (pH = 6.0 ± 0.1). Flumetsulam was monitored to a depth of 122 cm at 28, 56, and 84 days after treatment (DAT). Flumetsulam concentrations were determined by cotton bioassay, with separate standard curves for various soil–depth combinations. Following a preemergence application of flumetsulam at 224 g ai ha−1, the herbicide was primarily limited to the upper 8 cm of soil, regardless of soil type, year, or DAT. Exceptions to this typically occurred following substantial rainfall amounts early in the season. Beyond 28 DAT, no significant concentrations of flumetsulam were detected below 15 cm. Results from this research suggest that leaching is not a significant route of flumetsulam dissipation in the field.

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On the chemical dynamics of extracellular polysaccharides in the high Arctic surface microlayer

Ocean Science ◽

10.5194/os-8-401-2012 ◽

2012 ◽

Vol 8 (4) ◽

pp. 401-418 ◽

Cited By ~ 42

Author(s):

Q. Gao ◽

C. Leck ◽

C. Rauschenberg ◽

P. A. Matrai

Keyword(s):

Molecular Weight ◽

Organic Matter ◽

Compositional Analysis ◽

Physicochemical Characteristics ◽

High Arctic ◽

The Arctic ◽

Extracellular Polysaccharides ◽

Surface Microlayer ◽

Biological Origin ◽

Ocean Study

Abstract. The surface microlayer (SML) represents a unique system of which the physicochemical characteristics may differ from those of the underlying subsurface seawater (SSW). Within the Arctic pack ice area, the SML has been characterized as enriched in small colloids of biological origin, resulting from extracellular polymeric secretions (EPS). During the Arctic Summer Cloud Ocean Study (ASCOS) in August 2008, particulate organic matter (POM, with size range > 0.22 μm) and dissolved organic matter (DOM, < 0.22 μm, obtained after filtration) samples were collected and chemically characterized from the SML and the corresponding SSW at an open lead centered at 87.5° N and 5° E. Total organic carbon was persistently enriched in the SML with a mean enrichment factor (EF) of 1.45 ± 0.41, whereas sporadic depletions of dissolved carbohydrates and amino acids were observed. Monosaccharide compositional analysis reveals that EPS in the Arctic lead was formed mainly of distinctive heteropolysaccharides, enriched in xylose, fucose and glucose. The mean concentrations of total hydrolysable neutral sugars in SSW were 94.9 ± 37.5 nM in high molecular weight (HMW) DOM (> 5 kDa) and 64.4 ± 14.5 nM in POM. The enrichment of polysaccharides in the SML appeared to be a common feature, with EFs ranging from 1.7 to 7.0 for particulate polysaccharides and 3.5 to 12.1 for polysaccharides in the HMW DOM fraction. A calculated monosaccharide yield suggests that polymers in the HMW DOM fraction were scavenged, without substantial degradation, into the SML. Bubble scavenging experiments showed that newly aggregated particles could be formed abiotically by coagulation of low molecular weight nanometer-sized gels. Aerosol particles, artificially generated by bubbling experiments, were enriched in polysaccharides by factors of 22–70, relative to the source seawater. We propose that bubble scavenging of surface-active polysaccharides could be one of the possible mechanisms for the enrichment of polysaccharides in the high Arctic open lead SML.

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Biodestructive processes occurring in the organic matter of lowland peat in the arctic zone

10.1063/1.4966515 ◽

2016 ◽

Cited By ~ 1

Author(s):

L. I. Svarovskaya ◽

L. K. Altunina ◽

O. V. Serebrennikova

Keyword(s):

Organic Matter ◽

The Arctic ◽

Arctic Zone

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Permafrost-Affected Soils of the Russian Arctic and their Carbon Pools

Solid Earth Discussions ◽

10.5194/sed-6-619-2014 ◽

2014 ◽

Vol 6 (1) ◽

pp. 619-655

Author(s):

S. Zubrzycki ◽

L. Kutzbach ◽

E.-M. Pfeiffer

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Carbon Sink ◽

Global Climate ◽

Fundamental Property ◽

Climate System ◽

The Arctic ◽

Quaternary Period ◽

Permafrost Regions

Abstract. Permafrost-affected soils have accumulated enormous pools of organic matter during the Quaternary Period. The area occupied by these soils amounts to more than 8.6 million km2, which is about 27% of all land areas north of 50° N. Therefore, permafrost-affected soils are considered to be one of the most important cryosphere elements within the climate system. Due to the cryopedogenic processes that form these particular soils and the overlying vegetation that is adapted to the arctic climate, organic matter has accumulated to the present extent of up to 1024 Pg (1 Pg = 1015 g = 1 Gt) of soil organic carbon stored within the uppermost three meters of ground. Considering the observed progressive climate change and the projected polar amplification, permafrost-affected soils will undergo fundamental property changes. Higher turnover and mineralization rates of the organic matter are consequences of these changes, which are expected to result in an increased release of climate-relevant trace gases into the atmosphere. As a result, permafrost regions with their distinctive soils are likely to trigger an important tipping point within the global climate system, with additional political and social implications. The controversy of whether permafrost regions continue accumulating carbon or already function as a carbon source remains open until today. An increased focus on this subject matter, especially in underrepresented Siberian regions, could contribute to a more robust estimation of the soil organic carbon pool of permafrost regions and at the same time improve the understanding of the carbon sink and source functions of permafrost-affected soils.

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