The authors acknowledge the Water Quality Analysis Laboratory at the University of New Hampshire for assistance with sample analysis. The authors also thank two anonymous reviewers whose comments have helped to improve the manuscript. This work is funded by the National Science Foundation (DEB-1556603). Partial funding was also provided by the EPSCoR Ecosystems and Society Project (NSF EPS-1101245), New Hampshire Agricultural Experiment Station (Scientific Contribution #2662, USDA National Institute of Food and Agriculture (McIntire-Stennis) Project (1006760), the University of New Hampshire Graduate School, and the New Hampshire Water Resources Research Center.

<ol>
	<li>Brookshire, E. N. J., Valett, H. M., Thomas, S. A., Webster, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atmospheric+N+deposition+increases+organic+N+loss+from+temperate+forests.">Atmospheric N deposition increases organic N loss from temperate forests.</a> Ecosystems. 10 (2), 252-262 (2007).</li><li>Bernhardt, E. S., McDowell, W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Twenty+years+apart:+Comparisons+of+DOM+uptake+during+leaf+leachate+releases+to+Hubbard+Brook+Valley+streams+in+1979+and+2000.">Twenty years apart: Comparisons of DOM uptake during leaf leachate releases to Hubbard Brook Valley streams in 1979 and 2000.</a> J Geophys Res. 113, G03032 (2008).</li><li>Taylor, P. G., Townsend, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stoichiometric+control+of+organic+carbon-nitrate+relationships+from+soils+to+sea.">Stoichiometric control of organic carbon-nitrate relationships from soils to sea.</a> Nature. 464, 1178-1181 (2010).</li><li>Mulholland, P. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stream+denitrification+across+biomes+and+its+response+to+anthropogenic+nitrate+loading.">Stream denitrification across biomes and its response to anthropogenic nitrate loading.</a> Nature. 452, 202-205 (2008).</li><li>Tank, J. L., Rosi-Marshall, E. J., Baker, M. A., Hall, R. 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The authors have nothing to disclose.

Das Ziel des Nährstoffs Impulsverfahren, wie hier dargestellt, ist die Antwort des sehr unterschiedlichen Pool von Umgebungsfließgewässer DOM über einen Dynamikbereich eines zugegebenen anorganischen Nährstoff zu charakterisieren und zu quantifizieren. Wenn die zugegebene gelöste Stoff in ausreichendem Maße die Konzentration des reaktiven gelösten Stoffs zunimmt, kann eine große folgernd Raum geschaffen werden, um zu verstehen, wie die biogeochemischen Kreisläufe von DOM zu Nährstoffkonzentrationen verknüpft...

Gelöste organische Stoffe (DOM) ist eine wichtige Energie- und Nährstoffquelle Ökosysteme Süßwasser und ist als organische Substanz definiert, die ein 0,7-um-Filter durchläuft. Innerhalb von aquatischen Ökosystemen kann DOM auch Lichtdämpfung und Metallkomplexbildung beeinflussen. DOM ist ein sehr vielfältig und heterogene Mischung von organischen Verbindungen mit verschiedenen funktionellen Gruppen, sowie essentielle Nährstoffe wie Stickstoff (N) und Phosphor (P). Während der Begriff &quot;DOM&quot; beschreibt den gesamten Pool einschließlich ihrer C, N und P-Komponenten, wird seine Konzentration gelöster organischer Kohlenstoff (DOC) gemessen. Die inhärente molekulare Komplexität des DOM-Pool jedoch schafft Herausforderungen zu seiner Studie. Beispielsweise gibt es keinen direkten Weg, um den Bruchteil der gesamten DOM Pool von organischen Nährstoffen wie gelösten organischen Stickstoff (DON) und des gelösten organischen Phosphor (DOP) umfaßte zu messen. Stattdessen muss die Konzentration an organischen Nährstoffen durch Differenz bestimmt werden ( <em&gt; zB [DON] = [gesamte gelöste Stickstoff] - [gelösten anorganischen Stickstoff]). eine realistische DOM Änderung in einen Stream hinzuzufügen ist aufgrund der Vielfalt der Umgebungs DOM Pool schwierig. Frühere Studien haben einzelne Kohlenstoffquellen hinzugefügt (zB Glucose, Harnstoff 1) oder eine bestimmte Quelle wie Blattsänfte Sickerwasser 2 bis Konzentrationen im Bereich manipulieren. Jedoch sind diese Quellen nicht besonders repräsentativ für die Umgebungs DOM-Pool. Der Versuch , zu verfeinern oder Umgebungs DOM für nachfolgende Experimente konzentrieren auch mit Schwierigkeiten , einschließlich der Verlust bestimmter Fraktionen (zB hochlabile Komponenten) während der Verarbeitung eingewirkt ist. Als Ergebnis ist es schwierig, die Bedienelemente auf der Umgebungs DOM Pool zu verstehen, wie wir derzeit keine Methode besitzen, um direkt die Umgebungs DOM Pool manipulieren. Da jedoch die Biogeochemie von DOM ist mit Nährstoffen üblicherweise in der Umwelt (z nitrate [NO 3 -] 3), können wir andere gelöste Stoffe hinzufügen Ökosysteme zu streamen und die Reaktion des DOM - Pool zu diesen Manipulationen zu messen. Durch die Untersuchung, wie die DOM Pool reagiert auf eine breite Palette von experimentell verhängten Nährstoffkonzentrationen wir hoffen, einen besseren Einblick in zu gewinnen, wie DOM reagiert Umweltbedingungen fluktuiert. Ein Verfahren, das üblicherweise in Strom Biogeochemie verwendet wird, ist der Nährstoffzugabe Methode. Nährstoffzugabe Experimente haben traditionell verwendet worden , Aufnahmekinetik oder das Schicksal des zusätzlichen gelösten Stoff 4,5,6,7 zu verstehen. Nährstoff Additionen können kurzfristige auf dem hr 6 bis Tag Skala 4 oder längerfristigen Manipulationen im Laufe mehrerer Jahre 8 sein. Nährstoff Additionen kann auch das isotopisch markierte Nährstoffe ( zum Beispiel 15 N-NO 3 -) durch biogeochemischen Reaktionen hinzugefügt Nährstoff zu verfolgen. Allerdings isotopenbasierten Studien sind oft Expensive und erfordern anspruchsvolle Analysen (zB Verdaus) der mehreren Kammern benthic wo isotopisch markierte Nährstoffe zurückgehalten werden kann. Kürzliche Versuche haben den Nutzen der kurzfristigen Nährstoffimpulse ergeben , die Steuerelemente auf nicht hinzugefügt und Umgebungs Solute wie DOM 9,10, offenbart einen neuen Weg zu erläutern , durch die Echtzeit - in - situ - biogeochemischen Reaktionen zu untersuchen. Hier beschreiben wir und zeigen die wichtigsten methodischen Schritte zur Durchführung von kurzfristigen Nährstoff Impulse mit dem Ziel, das Verständnis der gekoppelten biogeochemischen von C und N und insbesondere die Kontrollen auf der sehr unterschiedlichen DOM-Pool. Dies leicht reproduzierbares Verfahren beinhaltet die Zugabe eines Nährstoffs Impuls zu einem experimentellen Strom erreichen und Veränderungen in der Konzentration von sowohl der Stell gelöstem Stoff und der Antwortvariablen von Interesse (zB DOC, DON, DOP) zu messen. Durch die direkte Nährstoffkonzentrationen in situ Manipulation wir sind in der Lage , um indirekt die DOM verändernPool und untersuchen , wie DOM Konzentrationsänderungen über einen Dynamikbereich von Nährstoffkonzentrationen 10.

<table><tbody><tr><td>Sodium Nitrate</td><td>Any</td><td>Any</td><td></td></tr><tr><td>Sodium Chloride</td><td>Any</td><td>Any</td><td>Store purchased table salt can be used as well, however, it does contain trace levels of impurities</td></tr><tr><td>Whatman GFF glass-fiber filters</td><td>Any</td><td>Any</td><td></td></tr><tr><td>BD Filtering Syringe</td><td>Any</td><td>Any</td><td></td></tr><tr><td>EMD Millipore Swinnex Filter Holders</td><td>Any</td><td>Any</td><td></td></tr><tr><td>Syringe stop-cock</td><td>Any</td><td>Any</td><td></td></tr><tr><td>YSI Multi-parameter probe</td><td>Yellow Springs International</td><td>556-01</td><td></td></tr><tr><td>Wide mouth HDPE 125 ml bottles</td><td>Any</td><td>Any</td><td></td></tr><tr><td>60 ml HDPE bottles</td><td>Any</td><td>Any</td><td></td></tr><tr><td>20 L bucket</td><td>Any</td><td>Any</td><td></td></tr><tr><td>Field measuring tape</td><td>Any</td><td>Any</td><td></td></tr><tr><td>Lab labeling tape</td><td>Any</td><td>Any</td><td></td></tr><tr><td>Stir stick</td><td>Any</td><td>Any</td><td></td></tr><tr><td>Cooler</td><td>Any</td><td>Any</td><td></td></tr><tr><td>Sharpie pen</td><td>Any</td><td>Any</td><td></td></tr><tr><td>Field notebook</td><td>Any</td><td>Any</td><td></td></tr><tr><td>Tweezers</td><td>Any</td><td>Any</td><td></td></tr><tr><td>Zip-lock bags</td><td>Any</td><td>Any</td><td></td></tr></tbody></table>

understanding dissolved organic matter biogeochemistry through in situ nutrient manipulations in stream ecosystems

Dissolved organic matter (DOM) is a highly diverse mixture of molecules providing one of the largest sources of energy and nutrients to stream ecosystems. Yet the in situ study of DOM is difficult as the molecular complexity of the DOM pool cannot be easily reproduced for experimental purposes. Nutrient additions to streams however, have been shown to repeatedly alter the in situ and ambient DOM pool. Here we demonstrate an easily replicable field-based method for manipulating the ambient pool of DOM at the ecosystem scale. During nutrient pulse experiments changes in the concentration of both dissolved organic carbon and dissolved organic nitrogen can be examined across a wide-range of nutrient concentrations. This method allows researchers to examine the controls on the DOM pool and make inferences regarding the role and function that certain fractions of the DOM pool play within ecosystems. We advocate the use of this method as a technique to help develop a deeper understanding of DOM biogeochemistry and how it interacts with nutrients. With further development this method may help elucidate the dynamics of DOM in other ecosystems.

<img alt="Figur 3" src="/files/ftp_upload/54704/54704fig3.jpg" /> Abbildung 3:. Beispiel Ergebnisse von Nitrat (NO 3 -) Zugänge mit Gelöster organischer Stickstoff (DON) als Reaktionsvariable Analysen sind lineare Regressionen. Sternchen stellen statistische Signifikanz bei α = 0,05. Beachten Sie den Dynamikbereich in NO 3 - Konzentration , die mit dem Nährstoff Pulsve...

Watch this Scientific Journal Video about Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems at JoVE.com

Verständnis der Biogeochemie gelöster organischer Materie durch In-situ-Nährstoffmanipulationen in Bachökosystemen | Umwelt | Video

Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems

Gelöste organische Materie stellt eine wichtige Quelle von Energie und Nährstoffen Ökosysteme zu streamen. Hier zeigen wir eine feldbasierte Methode , um die Umgebungs Pool von gelösten organischen Stoffen in situ durch leicht replizierbar Nährstoffimpulse zu manipulieren.

Organische Substanzen Biogeochemie Gelöster Verständnis durch<em&gt; In Situ</em&gt; Nährstoff Manipulations in Stream-Ecosystems

Dissolved organic matter (DOM) is a highly diverse mixture of molecules providing one of the largest sources of energy and nutrients to stream ecosystems. ...

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Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems

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10.1K Aufrufe.  University of New Hampshire.  Gelöste organische Materie stellt eine wichtige Quelle von Energie und Nährstoffen Ökosysteme zu streamen. Hier zeigen wir eine feldbasierte Methode , um die Umgebungs Pool von gelösten organischen Stoffen in situ durch leicht replizierbar Nährstoffimpulse zu manipulieren. 

Serie: Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems

Unraveling the Unseen Players in the Ocean - A Field Guide to Water Chemistry and Marine Microbiology

Here we introduce a series of thoroughly tested and well standardized research protocols adapted for use in remote marine environments. The sampling protocols include the assessment of resources available to the microbial community (dissolved organic carbon, particulate organic matter, inorganic nutrients), and a comprehensive description of the viral and bacterial communities (via direct viral and microbial counts, enumeration of autofluorescent microbes, and construction of viral and microbial metagenomes). We use a combination of methods, which represent a dispersed field of scientific disciplines comprising already established protocols and some of the most recent techniques developed. Especially metagenomic sequencing techniques used for viral and bacterial community characterization, have been established only in recent years, and are thus still subjected to constant improvement. This has led to a variety of sampling and sample processing procedures currently in use. The set of methods presented here provides an up to date approach to collect and process environmental samples. Parameters addressed with these protocols yield the minimum on information essential to characterize and understand the underlying mechanisms of viral and microbial community dynamics. It gives easy to follow guidelines to conduct comprehensive surveys and discusses critical steps and potential caveats pertinent to each technique.

Here, we present a comprehensive protocol to assess the organic and inorganic nutrient availability and the abundance and structure of microbial and viral communities in remote marine environments.

Entwirren der unsichtbaren Spieler im Ozean - ein Feld Führer zu Wasserchemie und Marine Mikrobiologie

Here we introduce a series of thoroughly tested and well standardized research protocols adapted for use in remote marine environments. The sampling ...

Forschung

Umwelt

Chemotactic Response of Marine Micro-Organisms to Micro-Scale Nutrient Layers

The degree to which planktonic microbes can exploit microscale resource patches will have considerable implications for oceanic trophodynamics and biogeochemical flux. However, to take advantage of nutrient patches in the ocean, swimming microbes must overcome the influences of physical forces including molecular diffusion and turbulent shear, which will limit the availability of patches and the ability of bacteria to locate them. Until recently, methodological limitations have precluded direct examinations of microbial behaviour within patchy habitats and realistic small-scale flow conditions. Hence, much of our current knowledge regarding microbial behaviour in the ocean has been procured from theoretical predictions. To obtain new information on microbial foraging behaviour in the ocean we have applied soft lithographic fabrication techniques to develop 2 microfluidic devices, which we have used to create (i) microscale nutrient patches with dimensions and diffusive characteristics relevant to oceanic processes and (ii) microscale vortices, with shear rates corresponding to those expected in the ocean. These microfluidic devices have permitted a first direct examination of microbial swimming and chemotactic behaviour within a heterogeneous and dynamic seascape. The combined use of epifluorescence and phase contrast microscopy allow direct examinations of the physical dimensions and diffusive characteristics of nutrient patches, while observing the population-level aggregative response, in addition to the swimming behaviour of individual microbes. These experiments have revealed that some species of phytoplankton, heterotrophic bacteria and phagotrophic protists are adept at locating and exploiting diffusing microscale resource patches within very short time frames. We have also shown that up to moderate shear rates, marine bacteria are able to  fight the flow  and swim through their environment at their own accord. However, beyond a threshold high shear level, bacteria are aligned in the shear flow and are less capable of swimming without disturbance from the flow. Microfluidics represents a novel and inexpensive approach for studying aquatic microbial ecology, and due to its suitability for accurately creating realistic flow fields and substrate gradients at the microscale, is ideally applicable to examinations of microbial behaviour at the smallest scales of interaction.  We therefore suggest that microfluidics represents a valuable tool for obtaining a better understanding of the ecology of microorganisms in the ocean.

The fabrication of microfluidic channels and their implementation in experiments for studying the chemotactic foraging behaviour of marine microbes within a patchy nutrient seascape and the swimming behaviour of bacteria within shear flow are described.

Chemotaktische Reaktion der marinen Mikroorganismen zu Micro-Scale Nutrient Layers

The degree to which planktonic microbes can exploit microscale resource patches will have considerable implications for oceanic trophodynamics and ...

Biologie

The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations

The measurement of sediment-water exchange of gases and solutes in aquatic sediments provides data valuable for understanding the role of sediments in nutrient and gas cycles. After cores with intact sediment-water interfaces are collected, they are submerged in incubation tanks and kept under aerobic conditions at in situ temperatures. To initiate a time course of overlying water chemistry, cores are sealed without bubbles using a top cap with a suspended stirrer. Time courses of 4-7 sample points are used to determine the rate of sediment water exchange. Artificial illumination simulates day-time conditions for shallow photosynthetic sediments, and in conjunction with dark incubations can provide net exchanges on a daily basis. The net measurement of N2 is made possible by sampling a time course of dissolved gas concentrations, with high precision mass spectrometric analysis of N2:Ar ratios providing a means to measure N2 concentrations. We have successfully applied this approach to lakes, reservoirs, estuaries, wetlands and storm water ponds, and with care, this approach provides valuable information on biogeochemical balances in aquatic ecosystems.

The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations

Here, we present small core incubations for the measurement of sediment-water gas and solute exchange. These will provide reliable measurements of sediment-water exchange that assess the role of sediment in influencing biological and biogeochemical processes in aquatic ecosystems.

Die Benthic Austausch von O<sub&gt; 2</sub&gt;, N<sub&gt; 2</sub&gt; Und gelöste Nährstoffe mit kleinen Kern Inkubationen

The measurement of sediment-water exchange of gases and solutes in aquatic sediments provides data valuable for understanding the role of sediments in ...

A Simple Approach to Manipulate Dissolved Oxygen for Animal Behavior Observations

The ability to manipulate dissolved oxygen (DO) in a laboratory setting has significant application to investigate a number of ecological and organismal behavior questions. The protocol described here provides a simple, reproducible, and controlled method to manipulate DO to study behavioral response in aquatic organisms resulting from hypoxic and anoxic conditions. While performing degasification of water with nitrogen is commonly used in laboratory settings, no explicit method for ecological (aquatic) application exists in the literature, and this protocol is the first to describe a protocol to degasify water to observe organismal response. This technique and protocol were developed for direct application for aquatic macroinvertebrates; however, small fish, amphibians, and other aquatic vertebrates could be easily substituted. It allows for easy manipulation of DO levels ranging from 2 mg/L to 11 mg/L with stability for up to a 5 min animal-observation period. Beyond a 5 min observation period water temperatures began to rise, and at 10 min DO levels became too unstable to maintain. The protocol is scalable to the study organism, reproducible, and reliable, allowing for rapid implementation into introductory teaching labs and high-level research applications. The expected results of this technique should relate dissolved oxygen changes to behavioral responses of organisms.

This article describes a simple and reproducible protocol to manipulate dissolved oxygen conditions in a laboratory setting for animal behavior studies. This protocol may be used in both teaching and research laboratory settings to evaluate organismal response of macroinvertebrates, fishes, or amphibians to changes in dissolved oxygen concentration.

Ein einfacher Ansatz zur Manipulation von gelöstem Sauerstoff für Tierverhaltensbeobachtungen

The ability to manipulate dissolved oxygen (DO) in a laboratory setting has significant application to investigate a number of ecological and organismal ...

Soil Lysimeter Excavation for Coupled Hydrological, Geochemical, and Microbiological Investigations

Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled Earth-system processes. Such knowledge is imperative in improving predictions of hydro-biogeochemical cycles, especially under climate change scenarios. We present an experimental method, designed to capture sub-surface heterogeneity of an initially homogeneous soil system. This method is based on destructive sampling of a soil lysimeter designed to simulate a small-scale hillslope. A weighing lysimeter of one cubic meter capacity was divided into sections (voxels) and was excavated layer-by-layer, with sub samples being collected from each voxel. The excavation procedure was aimed at detecting the incipient heterogeneity of the system by focusing on the spatial assessment of hydrological, geochemical, and microbiological properties of the soil. Representative results of a few physicochemical variables tested show the development of heterogeneity. Additional work to test interactions between hydrological, geochemical, and microbiological signatures is planned to interpret the observed patterns. Our study also demonstrates the possibility of carrying out similar excavations in order to observe and quantify different aspects of soil-development under varying environmental conditions and scale.

This study presents an excavation method for investigating subsurface hydrological, geochemical, and microbiological heterogeneity of a soil lysimeter. The lysimeter simulates an artificial hillslope which was initially under homogeneous condition and had been subjected to approximately 5,000 mm of water over eight cycles of irrigation in an 18-month period.

Boden Lysimeter Ausgrabung Gekoppelte hydrologische, geochemische und mikrobiologische Untersuchungen

Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled ...

Single-throughput Complementary High-resolution Analytical Techniques for Characterizing Complex Natural Organic Matter Mixtures

Natural organic matter (NOM) is composed of a highly complex mixture of thousands of organic compounds which, historically, proved difficult to characterize. However, to understand the thermodynamic and kinetic controls on greenhouse gas (carbon dioxide [CO2] and methane [CH4]) production resulting from the decomposition of NOM, a molecular-level characterization coupled with microbial proteome analyses is necessary. Further, climate and environmental changes are expected to perturb natural ecosystems, potentially upsetting complex interactions that influence both the supply of organic matter substrates and the microorganisms performing the transformations. A detailed molecular characterization of the organic matter, microbial proteomics, and the pathways and transformations by which organic matter is decomposed will be necessary to predict the direction and magnitude of the effects of environmental changes. This article describes a methodological throughput for comprehensive metabolite characterization in a single sample by direct injection Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), gas chromatography mass spectrometry (GC-MS), nuclear magnetic resonance (NMR) spectroscopy, liquid chromatography mass spectrometry (LC-MS), and proteomics analysis. This approach results in a fully-paired dataset which improves statistical confidence for inferring pathways of organic matter decomposition, the resulting CO2 and CH4 production rates, and their responses to environmental perturbation. Herein we present results of applying this method to NOM samples collected from peatlands; however, the protocol is applicable to any NOM sample (e.g., peat, forested soils, marine sediments, etc.).

This protocol describes a single throughput for complementary analytical and omics techniques culminating in a fully-paired characterization of natural organic matter and microbial proteomics in different ecosystems. This approach permits robust comparisons for identifying metabolic pathways and transformations important for describing greenhouse gas production and predicting responses to environmental change.

Single-Durchsatz ergänzende hochauflösende Analysetechniken für die Charakterisierung von komplexen natürlichen organischen Substanz Mischungen

Natural organic matter (NOM) is composed of a highly complex mixture of thousands of organic compounds which, historically, proved difficult to ...

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

The importance of understanding the fate of nitrate (NO3&#8722;), which is the dominant N species transferred from terrestrial to aquatic ecosystems, has been increasing because global nitrogen loads have dramatically increased following industrialization. Dissimilatory nitrate reduction to ammonium (DNRA) and denitrification are both microbial processes that use NO3&#8722; for respiration. Compared to denitrification, quantitative determinations of the DNRA activity have been carried out only to a limited extent. This has led to an insufficient understanding of the importance of DNRA in NO3&#8722; transformations and the regulating factors of this process. The objective of this paper is to provide a detailed procedure for the measurement of the potential DNRA rate in environmental samples. In brief, the potential DNRA rate can be calculated from the 15N-labeled ammonium (15NH4+) accumulation rate in 15NO3&#8722; added incubation. The determination of the 14NH4+ and 15NH4+ concentrations described in this paper is comprised of the following steps. First, the NH4+ in the sample is extracted and trapped on an acidified glass filter as ammonium salt. Second, the trapped ammonium is eluted and oxidized to NO3&#8722; via persulfate oxidation. Third, the NO3&#8722; is converted to N2O via an N2O reductase deficient denitrifier. Finally, the converted N2O is analyzed using a previously developed quadrupole gas chromatography&#8211;mass spectrometry system. We applied this method to salt marsh sediments and calculated their potential DNRA rates, demonstrating that the proposed procedures allow a simple and more rapid determination compared to previously described methods.

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

A series of methods to determine the potential DNRA rate based on 14NH4+/15NH4+ analyses is provided in detail. NH4+ is converted into N2O via several steps and analyzed using quadrupole gas chromatography&#8211;mass spectrometry.

Messung der potenzialimilatorischen Nitratreduktion zu Ammonium basierend auf 14NH4+/15NH4+ Analysen mittels Sequenzielle Umwandlung in N 2O

The importance of understanding the fate of nitrate (NO3&#8722;), which is the dominant N species transferred from terrestrial to aquatic ecosystems, has ...

Two-Dimensional Visualization and Quantification of Labile, Inorganic Plant Nutrients and Contaminants in Soil

We describe a method for two-dimensional (2D) visualization and quantification of the distribution of labile (i.e., reversibly adsorbed) inorganic nutrient (e.g., P, Fe, Mn) and contaminant (e.g., As, Cd, Pb) solute species in the soil adjacent to plant roots (the &#8216;rhizosphere&#8217;) at sub-millimeter (~100 &#181;m) spatial resolution. The method combines sink-based solute sampling by the diffusive gradients in thin films (DGT) technique with spatially resolved chemical analysis by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The DGT technique is based on thin hydrogels with homogeneously distributed analyte-selective binding phases. The variety of available binding phases allows for the preparation of different DGT gel types following simple gel fabrication procedures. For DGT gel deployment in the rhizosphere, plants are grown in flat, transparent growth containers (rhizotrons), which enable minimal invasive access to a soil-grown root system. After a pre-growth period, DGT gels are applied to selected regions of interest for in situ solute sampling in the rhizosphere. Afterwards, DGT gels are retrieved and prepared for subsequent chemical analysis of the bound solutes using LA-ICP-MS line-scan imaging. Application of internal normalization using 13C and external calibration using matrix-matched gel standards further allows for the quantification of the 2D solute fluxes. This method is unique in its capability to generate quantitative, sub-mm scale 2D images of multi-element solute fluxes in soil-plant environments, exceeding the achievable spatial resolution of other methods for measuring solute gradients in the rhizosphere substantially. We present the application and evaluation of the method for imaging multiple cationic and anionic solute species in the rhizosphere of terrestrial plants and highlight the possibility of combining this method with complementary solute imaging techniques.

This protocol presents a workflow for sub-mm 2D visualization of multiple labile inorganic nutrient and contaminant solute species using diffusive gradients in thin films (DGT) combined with mass spectrometry imaging. Solute sampling and high-resolution chemical analysis are described in detail for quantitative mapping of solutes in the rhizosphere of terrestrial plants.

Zweidimensionale Visualisierung und Quantifizierung von labilen, anorganischen Pflanzennährstoffen und Verunreinigungen im Boden

We describe a method for two-dimensional (2D) visualization and quantification of the distribution of labile (i.e., reversibly adsorbed) inorganic ...

Dissolved Solute Sampling Across an Oxic-Anoxic Soil-Water Interface Using Microdialysis Profilers

Biogeochemical processes shift rapidly in both spatial (millimeter scale) and temporal (hour scale to day scale) dimensions at the oxic-anoxic interface in response to disturbances. Deciphering the rapid biogeochemical changes requires in situ, minimally invasive tools with high spatial and temporal sampling resolution. However, the available passive sampling devices are not very useful in many cases either due to their disposable nature or the complexity and extensive workload for sample preparation.
To address this problem, a microdialysis profiler with 33 individual polyethersulfone nanomembrane tubes (semipermeable, &#60;20 nm pore size) integrated into the one-dimensional skeleton (60 mm) was established to iteratively sample the dissolved compounds in porewater across the soil-water interface at a high resolution of 1.8 mm (outer diameter plus one spacing, i.e., 0.1 mm between probes). The sampling mechanism is based on the principle of concentration gradient diffusion. The automatic loading of degassed water allows minimal disturbance to the chemical species across the oxic-anoxic interface.
This paper describes the procedures of device setup and continuous porewater sampling across the soil-water interface on a daily basis. Concentration-depth profiles were selectively measured before (on Day 6) and after (on Day 7) disturbances induced by irrigation. The results showed that concentration-depth profiles were undergoing rapid changes, especially for redox-sensitive elements (i.e., iron and arsenic). These protocols can help investigate the biogeochemical responses across the soil-water interface under various disturbances caused by physical, chemical, and biological factors. The paper thoroughly discusses the advantages and disadvantages of this method for potential use in the environmental sciences.

A microdialysis profiler is described to sample dissolved porewater solutes across an oxic-anoxic soil-water interface in situ with minimal disturbance. This device is designed to capture rapid changes in concentration-depth profiles induced by disturbances at the soil-water interface and beyond.

Probenahme gelöster gelöster Stoffe an einer oxisch-anoxischen Boden-Wasser-Grenzfläche mit Mikrodialyse-Profilern

Biogeochemical processes shift rapidly in both spatial (millimeter scale) and temporal (hour scale to day scale) dimensions at the oxic-anoxic interface ...

Integrierte Visualisierung biogeochemischer Daten für das Nährstoffmanagement

Visualization of Productivity Zones Based on Nitrogen Mass Balance Model in Narragansett Bay, Rhode Island

Primary productivity in the coastal regions, linked to eutrophication and hypoxia, provides a critical understanding of ecosystem function. Although primary productivity largely depends on riverine nutrient inputs, estimation of the extent of riverine nutrient influences in the coastal regions is challenging. A nitrogen mass balance model is a practical tool to evaluate coastal ocean productivity to understand biological mechanisms beyond data observations. This study visualizes the biological production zones in Narragansett Bay, Rhode Island, USA, where hypoxia frequently occurs, by applying a nitrogen mass balance model. The Bay is divided into three zones - brown, green, and blue zones - based on primary productivity, which are defined by the mass balance model results. Brown, green, and blue zones represent a high physical process, a high biological process, and a low biological process zone, depending on river flow, nutrient concentrations, and mixing rates. The results of this study can better inform nutrient management in the coastal ocean in response to hypoxia and eutrophication.

Autor im Rampenlicht: Verständnis der Stickstoffauswirkungen und der Primärproduktivität in Flüssen für ein effektives Nährstoffmanagement

Here, we aim to visualize the zonation of biological productivity in Narragansett Bay, Rhode Island, based on the nitrogen mass balance model. The results will inform nutrient management in the coastal regions to reduce hypoxia and eutrophication.

Visualisierung von Produktivitätszonen basierend auf einem Stickstoffmassenbilanzmodell in Narragansett Bay, Rhode Island

Primary productivity in the coastal regions, linked to eutrophication and hypoxia, provides a critical understanding of ecosystem function. Although ...

Organische Substanzen Biogeochemie Gelöster Verständnis durch

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