An in situ mesocosm method for quantifying nitrogen cycling rates in oligotrophic wetlands using 15N tracer techniques

Wetlands ◽  
2008 ◽  
Vol 28 (2) ◽  
pp. 502-512 ◽  
Author(s):  
Jeffrey R. Wozniak ◽  
Daniel L. Childers ◽  
William T. Anderson ◽  
David T. Rudnick ◽  
Christopher J. Madden
Keyword(s):  
Nitrogen Cycling ◽  
15N Tracer ◽  
Tracer Techniques

scholarly journals Quantifying Potential N Turnover Rates in Hypersaline Microbial Mats by Using 15N Tracer Techniques

2021 ◽  
Vol 87 (8) ◽  
Author(s):  
Oksana Coban ◽  
Olivia Rasigraf ◽  
Anniek E. E. de Jong ◽  
Oliver Spott ◽  
Brad M. Bebout
Keyword(s):  
Nitrogen Cycling ◽  
Microbial Mats ◽  
Ammonium Assimilation ◽  
15N Tracer ◽  
Turnover Rates ◽  
Overlying Water ◽  
N Cycle ◽  
Elkhorn Slough ◽  
Tracer Techniques ◽  
Morphological Differences

ABSTRACT Microbial mats, due to stratification of the redox zones, have the potential to include a complete N cycle; however, an attempt to evaluate a complete N cycle in these ecosystems has not been yet made. In this study, the occurrence and rates of major N cycle processes were evaluated in intact microbial mats from Elkhorn Slough, Monterey Bay, CA, USA, and Baja California Sur, Mexico, under oxic and anoxic conditions using 15N-labeling techniques. All the major N transformation pathways, with the exception of anammox, were detected in both microbial mats. Nitrification rates were found to be low at both sites for both seasons investigated. The highest rates of ammonium assimilation were measured in Elkhorn Slough mats in April and corresponded to high in situ ammonium concentrations in the overlying water. Baja mats featured higher ammonification than ammonium assimilation rates, and this, along with their higher affinity for nitrate compared to ammonium and low dissimilatory nitrate reduction to ammonium rates, characterized their differences from Elkhorn Slough mats. Nitrogen fixation rates in Elkhorn Slough microbial mats were found to be low, implying that other processes, such as recycling and assimilation from water, are the main sources of N for these mats at the times sampled. Denitrification in all the mats was incomplete, with nitrous oxide as the end product and not dinitrogen. Our findings highlight N cycling features not previously quantified in microbial mats and indicate a need for further investigations of these microbial ecosystems. IMPORTANCE Nitrogen is essential for life. The nitrogen cycle on Earth is mediated by microbial activity and has had a profound impact on both the atmosphere and the biosphere throughout geologic time. Microbial mats, present in many modern environments, have been regarded as living records of the organisms, genes, and phylogenies of microbes, as they are one of the most ancient ecosystems on Earth. While rates of major nitrogen metabolic pathways have been evaluated in a number of ecosystems, they remain elusive in microbial mats. In particular, it is unclear what factors affect nitrogen cycling in these ecosystems and how morphological differences between mats impact nitrogen transformations. In this study, we investigate nitrogen cycling in two microbial mats having morphological differences. Our findings provide insight for further understanding of biogeochemistry and microbial ecology of microbial mats.

Removal of nitrogen in different wetland filter materials: use of stable nitrogen isotopes to determine factors controlling denitrification and DNRA

2005 ◽  
Vol 51 (9) ◽  
pp. 63-71 ◽  
Author(s):  
P.T. Mørkved ◽  
A.K. Søvik ◽  
B. Kløve ◽  
L.R. Bakken
Keyword(s):  
Nitrogen Isotopes ◽  
Raw Materials ◽  
15N Tracer ◽  
Relative Role ◽  
Filter Materials ◽  
Tracer Techniques ◽  
Initial Oxygen ◽  
Materials Used ◽  
The One

Laboratory incubations with varying O2 and NO3 concentrations were performed with a range of filter materials used in constructed wetlands (CWs). The study included material sampled from functioning CWs as well as raw materials subjected to laboratory pre-incubation. 15N-tracer techniques were used to assess the rates of denitrification versus dissimilatory nitrate reduction to ammonium (DNRA), and the relative role of nitrification versus denitrification in producing N2O. The N2O/(N2+N2O) product ratio was assessed for the different materials. Sand, shell sand, and peat sustained high rates of denitrification. Raw light-weight aggregates (LWA) had a very low rate, while in LWA sampled from a functioning CW, the rate was similar to the one found in the other materials. The N2O/(N2+N2O) ratio was very low for sand, shell sand and LWA from functioning CWs, but very high for raw LWA. The ratio was intermediate but variable for peat. The N2O produced by nitrification accounted for a significant percentage of the N2O accumulated during the incubation, but was dependent on the initial oxygen concentration. DNRA was significant only for shell sand taken from a functioning CW, suggesting that the establishment of active DNRA is a slower process than the establishment of a denitrifying flora.

15N Tracer Techniques for the Differential Diagnosis of Dwarfism and Prediction of Growth Hormone Action in Children

1987 ◽  
Vol 65 (1) ◽  
pp. 74-77 ◽  
Author(s):  
INGO RICHTER ◽  
WILLI HEINE ◽  
CHRISTIAN PLATH ◽  
MONIKA MIX ◽  
KLAUS D. WUTZKE ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Differential Diagnosis ◽  
15N Tracer ◽  
Hormone Action ◽  
Tracer Techniques ◽  
Growth Hormone Action

Identification and quantification of nitrogen removal in a rotating biological contactor by 15N tracer techniques

2003 ◽  
Vol 37 (6) ◽  
pp. 1252-1259 ◽  
Author(s):  
Stijn Wyffels ◽  
Kris Pynaert ◽  
Pascal Boeckx ◽  
Willy Verstraete ◽  
Oswald Van Cleemput
Keyword(s):  
Nitrogen Removal ◽  
15N Tracer ◽  
Rotating Biological Contactor ◽  
Tracer Techniques ◽  
Identification And Quantification

Rhizosphere Volatile Organic Compounds: A real-time approach using diffusive soil probes on a controlled Tropical Rainforest

2020 ◽  
Author(s):  
Juliana Gil Loaiza ◽  
Laura Meredith ◽  
Jordan Krechmer ◽  
Megan Claflin ◽  
Rob Roscioli ◽  
...  
Keyword(s):  
High Resolution ◽  
Nitrogen Cycling ◽  
Organic Compounds ◽  
Tropical Rainforest ◽  
Environmental Changes ◽  
Soil Sampling ◽  
Subsurface Soil ◽  
Volatile Organic ◽  
Microbe Interactions

<p>Microbial metabolic functions and biogeochemical pathways of the complex rhizosphere-soil-microbe interactions change with aboveground vegetation and the ecosystem response to environmental changes. Soil trace gases and current genomic approaches have been valuable to characterize in-situ microbial activity. However, there is a lack of understanding of the complexity of the belowground processes, the time frame of microbial community responses to environmental changes and the degree to which microbial activity can be inferred current -omics approaches. In the nitrogen cycling at a field scale, microbial diversity or gene abundance sometimes does not explain N<sub>2</sub>O emissions or even gene expression, there some bacteria that cannot be cultivated, and in general –omics involve destructive soil sampling that is prone to changes of the in-situ soil conditions. Additionally, field soil sampling may not capture the heterogeneity of the soil or specific area of study.</p><p>Volatile Organic Compounds (VOCs) produced in the rhizosphere play an important role in microbial nutrient cycling. VOCs are produced by plants and microorganisms as a response to biotic or biotic stressors or the type of carbon sources available.</p><p>Here, we present how subsurface soil gas measurements in an enclosed ecosystem during the Water, Atmosphere, and Life Dynamics experiment (B2-WALD) at the Tropical Rainforest biome of Biosphere 2 (Arizona, USA) during an induced controlled drought. We present initial results of a unique non-destructive approach that simultaneously couples a) new hydrophobic-porous subsurface soil probes, b) high-resolution Tunable Infrared Laser Direct Absorption Spectrometers (TILDAS) to analyze in situ trace gas isotopomers, and c) a proton transfer reaction mass spectrometer (VOCUS, high resolution volatile organic compound gas analyzer) for VOC quantification. We measured soil gas isotopic composition of N<sub>2</sub>O and VOCs-- comparing rhizosphere and control areas before and during the drought. We will focus our discussion on VOCs and its potential as makers of microbial interactions and signaling as a response to an environmental stressor like drought.</p><p>In this project, we demonstrate the feasibility of online coupling of soil probes with high-resolution instrumentation to measure products from nitrogen cycling and nonmethane VOC production in soils as a response to soil-plant microbe interactions. In addition, this approach could be a potential tool to constraint inferences derived from different –omics approaches.</p>

Nitrogen cycling in a dryland stream ecosystem as determined by a 15N tracer experiment (LINX)

2000 ◽  
Vol 27 (1) ◽  
pp. 601-601
Author(s):  
Nancy B. Grimm ◽  
Eugenia Martí ◽  
Jennifer L. Tank
Keyword(s):  
Nitrogen Cycling ◽  
Tracer Experiment ◽  
15N Tracer ◽  
Stream Ecosystem

scholarly journals Predicting the denitrification capacity of sandy aquifers from in situ measurements using push-pull <sup>15</sup>N tracer tests

2014 ◽  
Vol 11 (12) ◽  
pp. 16527-16572 ◽  
Author(s):  
W. Eschenbach ◽  
R. Well ◽  
W. Walther
Keyword(s):  
Mass Spectrometry ◽  
Microbial Community ◽  
Isotope Ratio ◽  
Tracer Tests ◽  
Isotope Ratio Mass Spectrometry ◽  
In Situ Measurements ◽  
15N Tracer ◽  
Aquifer Material ◽  
15N Analysis

Abstract. Knowledge about the spatial variability of in situ denitrification rates (Dr(in situ)) and their relation to the denitrification capacity in nitrate-contaminated aquifers is crucial to predict the development of groundwater quality. Therefore, 28 push-pull 15N tracer tests for the measurement of in situ denitrification rates were conducted in two sandy Pleistocene aquifers in Northern Germany. The 15N analysis of denitrification derived 15N labelled N2 and N2O dissolved in water samples collected during the push-pull 15N tracer tests was performed by isotope ratio mass spectrometry (IRMS) in the lab and additionally for some tracer tests online in the field with a quadrupole membrane inlet mass spectrometer (MIMS), in order to test the feasibility of on-site real-time 15N analysis. Aquifer material from the same locations and depths as the push-pull injection points was incubated and the initial and cumulative denitrification after one year of incubation (Dcum(365)) as well as the stock of reduced compounds (SRC) was compared with in situ measurements of denitrification. This was done to derive transfer functions suitable to predict Dcum(365) and SRC from Dr(in situ). Dr(in situ) ranged from 0 to 51.5 μg N kg−1 d−1. Denitrification rates derived from on-site isotope analysis using membrane-inlet mass spectrometry satisfactorily coincided with laboratory analysis by conventional isotope ratio mass spectrometry, thus proving the feasibility of in situ analysis. Dr(in situ) was significantly higher in the sulphidic zone of both aquifers compared to the zone of non-sulphidic aquifer material. Overall, regressions between the Dcum(365) and SRC of the tested aquifer material with Dr(in situ) exhibited only a modest linear correlation for the full data set. But the predictability of Dcum(365) and SRC from Dr(in situ) data clearly increased for aquifer samples from the zone of NO3−-bearing groundwater. In the NO3−-free aquifer zone a lag phase of denitrification after NO3− injections was observed, which confounded the relationship between reactive compounds and in situ denitrification activity. This finding was attributed to adaptation processes in the microbial community after NO3− injections. Exemplarily, it was demonstrated that the microbial community in the NO3−-free zone close below the NO3−-bearing zone can be adapted to denitrification by amending wells with NO3−-injections for an extended period. In situ denitrification rates were 30 to 65% higher after pre-conditioning with NO3−. Results from this study suggest that such pre-conditioning is crucial for the measurement of Dr(in situ) in deeper aquifer material from the NO3−-free groundwater zone and thus for the prediction of Dcum(365) and SRC from Dr(in situ).

scholarly journals CARD-FISH in the Sequencing Era: Opening a New Universe of Protistan Ecology

2021 ◽  
Vol 12 ◽  
Author(s):  
Kasia Piwosz ◽  
Indranil Mukherjee ◽  
Michaela M. Salcher ◽  
Vesna Grujčić ◽  
Karel Šimek
Keyword(s):  
Food Webs ◽  
Size Fraction ◽  
Food Vacuole ◽  
Trophic Levels ◽  
Probe Design ◽  
Tracer Techniques ◽  
New Findings ◽  
Catalyzed Reporter Deposition ◽  
Card Fish

Phagotrophic protists are key players in aquatic food webs. Although sequencing-based studies have revealed their enormous diversity, ecological information on in situ abundance, feeding modes, grazing preferences, and growth rates of specific lineages can be reliably obtained only using microscopy-based molecular methods, such as Catalyzed Reporter Deposition-Fluorescence in situ Hybridization (CARD-FISH). CARD-FISH is commonly applied to study prokaryotes, but less so to microbial eukaryotes. Application of this technique revealed that Paraphysomonas or Spumella-like chrysophytes, considered to be among the most prominent members of protistan communities in pelagic environments, are omnipresent but actually less abundant than expected, in contrast to little known groups such as heterotrophic cryptophyte lineages (e.g., CRY1), cercozoans, katablepharids, or the MAST lineages. Combination of CARD-FISH with tracer techniques and application of double CARD-FISH allow visualization of food vacuole contents of specific flagellate groups, thus considerably challenging our current, simplistic view that they are predominantly bacterivores. Experimental manipulations with natural communities revealed that larger flagellates are actually omnivores ingesting both prokaryotes and other protists. These new findings justify our proposition of an updated model of microbial food webs in pelagic environments, reflecting more authentically the complex trophic interactions and specific roles of flagellated protists, with inclusion of at least two additional trophic levels in the nanoplankton size fraction. Moreover, we provide a detailed CARD-FISH protocol for protists, exemplified on mixo- and heterotrophic nanoplanktonic flagellates, together with tips on probe design, a troubleshooting guide addressing most frequent obstacles, and an exhaustive list of published probes targeting protists.

scholarly journals Microbial Community Diversity Associated with Carbon and Nitrogen Cycling in Permeable Shelf Sediments

2006 ◽  
Vol 72 (9) ◽  
pp. 5689-5701 ◽  
Author(s):  
Evan M. Hunter ◽  
Heath J. Mills ◽  
Joel E. Kostka
Keyword(s):  
Organic Matter ◽  
Nitrogen Cycling ◽  
Rrna Genes ◽  
Column Experiments ◽  
Ssu Rrna ◽  
Carbon And Nitrogen ◽  
Carbon And Nitrogen Cycling ◽  
In Situ Conditions ◽  
Shelf Sediments

ABSTRACT Though a large fraction of primary production and organic matter cycling in the oceans occurs on continental shelves dominated by sandy deposits, the microbial communities associated with permeable shelf sediments remain poorly characterized. Therefore, in this study, we provide the first detailed characterization of microbial diversity in marine sands of the South Atlantic Bight through parallel analyses of small-subunit (SSU) rRNA gene (Bacteria), nosZ (denitrifying bacteria), and amoA (ammonia-oxidizing bacteria) sequences. Communities were analyzed by parallel DNA extractions and clone library construction from both sediment core material and manipulated sediment within column experiments designed for geochemical rate determinations. Rapid organic-matter degradation and coupled nitrification-denitrification were observed in column experiments at flow rates resembling in situ conditions over a range of oxygen concentrations. Numerous SSU rRNA phylotypes were affiliated with the phyla Proteobacteria (classes Alpha-, Delta-, and Gammaproteobacteria), Planctomycetes, Cyanobacteria, Chloroflexi, and Bacteroidetes. Detectable sequence diversity of nosZ and SSU rRNA genes increased in stratified redox-stabilized columns compared to in situ sediments, with the Alphaproteobacteria comprising the most frequently detected group. Alternatively, nitrifier communities showed a relatively low and stable diversity that did not covary with the other gene targets. Our results elucidate predominant phylotypes that are likely to catalyze carbon and nitrogen cycling in marine sands. Although overall diversity increased in response to redox stabilization and stratification in column experiments, the major phylotypes remained the same in all of our libraries, indicating that the columns sufficiently mimic in situ conditions.

Diurnal Variation of Dissolved Inorganic Carbon and its Use in Estimating Primary Production and CO2 Invasion in Lake 227

1973 ◽  
Vol 30 (10) ◽  
pp. 1501-1510 ◽  
Author(s):  
D. W. Schindler ◽  
E. J. Fee
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Community Respiration ◽  
Phytoplankton Production ◽  
Carbon Limitation ◽  
Low Carbon ◽  
Nitrogen And Phosphorus ◽  
Natural Lakes ◽  
Tracer Techniques

Standard in situ measurements of phytoplankton production and 14C bottle bioassays gave erroneous results when applied to lake 227, a eutrophic softwater lake in the Canadian Shield. Errors were found to be due to diurnal variations in the degree of carbon limitation of phytoplankton, and to invasion of CO2 from the atmosphere and hypolimnion.A method based on diurnal measurements of dissolved inorganic carbon, community respiration, and invasion of CO2, using gas chromatography, is described. Production by phytoplankton in lakes fertilized with nitrogen and phosphorus was found to be several times higher than in natural lakes of the area. Net production during summer stratification was found to equal invasion of CO2 from the atmosphere.The new technique should have application in other eutrophic low carbon lakes, where 14C tracer techniques are encumbered by serious technical complications.

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