The Fate of 15 N-Nitrate in Healthy and Declining Phragmites australis Stands

Nijburg, J. W.; Laanbroek, Hendrikus J.

doi:10.1007/s002489900055

Cited by 33 publications

(12 citation statements)

References 28 publications

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“…Our results range from 0 to12% at the inflow stream ecotype to 6 to 99% at the lake ecotype and overlap with global freshwater data (Freshwater lakes: Nijburg & Laanbroek 1997b, Nizzoli et al 2010 wetlands: Ambus et al 1992, Scott et al 2008 streams: Kelso et al 1999, Omnes et al 1996 Fig. 6).…”

Section: Global Comparisonssupporting

confidence: 85%

“…The presence of certain macrophytes in low nitrate sediments may greatly increase the proportion of DNRA to denitrification, possibly due to increased C availability from root exudates and elevated O 2 levels, (Nijburg & Laanbroek 1997b). Aerenchymatous plants release O 2 into the root zone when healthy (Nijburg et al 1997), and this process in turn selects for DNRA over denitrification as DNRA is less inhibited by O 2 presence than denitrification, especially at high C:N ratios (Fazzolari et al 1998).…”

Section: Spatial Patterns In No 3 − Losses By Dissimilatory Pathwaysmentioning

confidence: 99%

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Dissimilatory nitrate reduction pathways in an oligotrophic freshwater ecosystem: spatial and temporal trends

Washbourne¹,

Crenshaw²,

Baker³

2011

Aquat. Microb. Ecol.

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Elevated nitrate (NO 3 − ) concentrations can cause eutrophication, which may lead to harmful algal blooms, loss of habitat and reduction in biodiversity. Denitrification, a dissimilatory process that removes NO 3 − mainly as dinitrogen gas (N 2 ), is believed to be the dominant NO 3 − removal pathway in aquatic ecosystems. Evidence suggests that a less well-studied process, dissimilatory nitrate reduction to ammonium (DNRA), which retains nitrogen (N) in the system, may also be important under favorable conditions. Using stable isotope tracers in sealed microcosms, we measured the potential for NO 3 − losses due to DNRA and denitrification in an oligotrophic freshwater ecosystem. We took sediment and water samples at runoff and baseflow, across several ecotypes. Our objective was to quantify the relative importance of DNRA compared to denitrification with changes in ecotype and season. Potential denitrification rates ranged from 0 to 0.14 ± 0.03 µgN gAFDM −1 d −1. Potential DNRA rates ranged from 0 to 0.0051 ± 0.0008 µgN gAFDM −1 d −1. Denitrification losses peaked at the inflow stream ecotype at 96.2% of total dissimilatory NO 3 − removal, whereas losses due to DNRA peaked in the lake ecotype at 34.4%. When averaged over the entire system, denitrification peaked at baseflow (31.2%), while DNRA peaked at runoff (2.9%). Although NO 3 − transformations due to denitrification were higher than DNRA in all ecotype and temporal comparisons, our results suggest that DNRA is also important under favorable conditions. KEY WORDS: DNRA · Denitrification · Nitrogen transformations · Ecotype · Season Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 65: [55][56][57][58][59][60][61][62][63][64] 2011 finally N 2 (Ye et al. 1995). The final reduction products, nitrous oxide (N 2 O), a potent greenhouse gas (Ramaswamy et al. 2001), and dinitrogen gas (N 2 ), are lost from the system into the atmosphere (Delwiche & Bryan 1976). In the presence of O 2 , most denitrifying bacteria will switch to the physiologically preferred process of aerobic respiration at the expense of NO 3 − reduction. (Megonigal et al. 2004). Denitrification may be diminished by the presence of free sulfides, which can inhibit the enzymes responsible for the final 2 stages of the process (Burgin & Hamilton 2007).DNRA is a microbial process that transforms NO 3 − to ammonium (NH 4 + ) via formation of NO 2 − in anaerobic or low O 2 environments. The final N form, NH 4 + , is bioavailable and readily immobilized by microbes and plants, or transformed by nitrification (Bengtsson et al. 2003). There are 2 DNRA pathways; fermentative and chemolithoautotrophic. Fermentative DNRA microbes reduce NO 3 − to NO 2 − to produce ATP. The subsequent reduction of NO 2 − to NH 4 + is an electron sink that allows re-oxidation of NADH (Tiedje 1988). Chemolithoautotrophic DNRA is the transformation of NO 3 − to NH 4 + , linked to oxidation of reduced sulfur (S) compounds. This sulfur-driven NO 3 − reduction leads to ...

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Section: Global Comparisonssupporting

confidence: 85%

Section: Spatial Patterns In No 3 − Losses By Dissimilatory Pathwaysmentioning

confidence: 99%

Dissimilatory nitrate reduction pathways in an oligotrophic freshwater ecosystem: spatial and temporal trends

Washbourne¹,

Crenshaw²,

Baker³

2011

Aquat. Microb. Ecol.

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“…In sediments of healthy and degrading P. australis stands, denitrification was the main nitrate-reducing process (Nijburg and Laanbroek, 1997a). Nitrate reduction to ammonium amounted to only a few per cent of the quantity of nitrate reduced to gaseous end-products.…”

Section: Nitrogen Cyclingmentioning

confidence: 97%

Methane emission from natural wetlands: interplay between emergent macrophytes and soil microbial processes. A mini-review

2009

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The role of the nitrogen cycle in repression of methane production is probably low. In contrast to wetlands particularly created for the purification of nitrogen-rich waste waters, concentrations of inorganic nitrogen compounds are low in the root zones in the growing season due to the nitrogen-consuming behaviour of the plant. Therefore, nitrate hardly competes with other electron acceptors for reduced organic compounds, and repression of methane oxidation by the presence of higher levels of ammonium will not be the case. The role of the iron cycle is likely to be important with respect to the repression of methane production and oxidation. Iron-reducing and iron-oxidizing bacteria are ubiquitous in the rhizosphere of wetland plants. The cycling of iron will be largely dependent on the size of the oxygen release in the root zone, which is likely to be different between different wetland plant species. The role of the sulfur cycle in repression of methane production is important in marine, sulfate-rich ecosystems, but might also play a role in freshwater systems where sufficient sulfate is available. Sulfate-reducing bacteria are omnipresent in freshwater ecosystems, but do not always react immediately to the supply of fresh sulfate. Hence, their role in the repression of methanogenesis is still to be proven in freshwater marshes.

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“…in the sediment may be oxidized to NO 3 -(nitrification) as a result of oxygen release from plant roots (Nijburg and Laanbroek 1997). Nitrogen added as NO 3 -to the NOX mesocosms might have diffused to anoxic zones in the sediment and was subsequently lost as N 2 gas through the denitrification process (Eriksson and Weisner 1999; Gribsholt and Kristensen 2002), which may have been stimulated through the presence of macrophytes.…”

Section: Tracer Uptake and Cyclingmentioning

confidence: 99%

“…Dense stands of P. australis may grow in wetlands, along the shores of rivers, lakes and ponds, and along roadsides (Campbell and Ogden 1999). Due to its adaptability and deep root structure, it is considered as an effective species for nutrient removal in both constructed wetlands (Tanner 1996;Nijburg and Laanbroek 1997;Vymazal 2013) and lakes (Sollie et al 2008). For rooted macrophytes, lake sediments are generally the primary source for the macronutrients N and P (Barko et al 1991).…”

Section: Introductionmentioning

confidence: 99%

Nitrogen uptake and cycling in Phragmites australis in a lake-receiving nutrient-rich mine water: a 15N tracer study

2015

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Uptake and cycling of nitrogen (N) in the littoral zone of a lake-receiving nutrient-rich mine water located in Boliden, northern Sweden, was investigated. Stable isotope tracer solutions of 15 N as NH 4? (NAM mesocosm) or NO 3 -(NOX mesocosm) were added to mesocosms enclosing plants of common reed (Phragmites australis). The 15 N abundance in various plant parts was measured at pre-defined time intervals over an experimental period of 22 days. During the course of the experiment, plant parts from the NAM mesocosms were significantly more enriched in 15 N than plant parts from the NOX mesocosms. On day 13, Dd 15 N values of the fine roots from the NAM mesocosms had reached ?8220 %, while the maximum Dd 15 N value in NOX roots was considerably lower at ?4430 %. Using 15 N values in macrophyte tissues present at the end of the experiment enabled calculations of uptake rates and % of tracer N recovered in the plant (%tracerNrecov). Maximum tracer uptake rates were higher for the NAM mesocosms (1.4 lg g -1 min -1 or 48 mg N m -2 d -1 ) compared to the NOX mesocosms (0.23 lg g -1 min -1 or 8.5 mg N m -2 d -1 ). Calculations of %tracerNrecov indicated that 1-8 and 25-44 % of added N was assimilated by plants in the NOX and NAM mesocosms, respectively. Hence, P. australis was more effective in assimilating NH 4 ? , and a larger portion of the tracer N accumulated in the roots compared to the other plant parts. Consequently, macrophyte N removal is most effective for cold-climate aquatic systems receiving mine water dominated by NH 4? . For permanent removal of N, the whole plant (including the roots) should be harvested.

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The Fate of 15 N-Nitrate in Healthy and Declining Phragmites australis Stands

Cited by 33 publications

References 28 publications

Dissimilatory nitrate reduction pathways in an oligotrophic freshwater ecosystem: spatial and temporal trends

Dissimilatory nitrate reduction pathways in an oligotrophic freshwater ecosystem: spatial and temporal trends

Methane emission from natural wetlands: interplay between emergent macrophytes and soil microbial processes. A mini-review

Nitrogen uptake and cycling in Phragmites australis in a lake-receiving nutrient-rich mine water: a 15N tracer study

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