Nitrogen fixation and 15N2 calibration of the acetylene reduction assay in coastal marine sediments

Seitzinger, S.; Garber, Jonathan

doi:10.3354/meps037065

Cited by 80 publications

(50 citation statements)

References 27 publications

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“…At the end of a 6 to 8 h incubation, depth profiles of acetylene reduction rates in the rhizosphere were made by taking duplicate 1 m1 sediment pore water samples with a syringe and needle through silicone-filled holes located at 2 cm intervals (1, 3, 5, ?, 9, 11, 13 cm depth) in the core wall. Twenty-four hour time course experiments confirmed that 6 to 8 h was the optimal incubation time in which a linear response could be measured accurately without the artifacts of a lag in response that can sometimes occur with too short a n incubation time (0.5 to 2 h), or of substrate depletion from too long an incubation time ( > l 2 h) (Capone 1982, Seitzinger & Garber 1987. The perfusion process took < 5 min per core and there was no visual indication of compaction of the core or channeling of the perfused pore water in the sandy sediments.…”

Section: Methodsmentioning

confidence: 69%

“…Acetylene reduction rates were related to nitrogen fixation rates using the stoichiometric relationship of 1 m01 dinitrogen fixed for every 3 m01 acetylene reduced. Though this ratio is known to vary in marine sediments (Seitzinger & Garber 1987), we based our calculations on the callbration of acetylene reduction with 15N2 fixation made by O'Donohue et al…”

Section: Methodsmentioning

confidence: 99%

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Temporal and spatial variation in nitrogen fixation activity in the eelgrass Zostera marina rhizosphere

McGlathery¹,

Risgaard-Petersen²,

Christensen³

1998

Mar. Ecol. Prog. Ser.

113

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Temporal and spatial variation in nitrogen fixation activity in the eelgrass Zostera marina rhizosphere Karen J. ~c~l a t h e r y ' r * , Nils R i s g a a r d -P e t e r s e n 2 , Peter Bondo christensen2 ABSTRACT: A perfusion technique for measuilng nitrogen fixation in the eelgrass rhizosphere was developed and used to investigate the patterns and controls of nitrogen fixatlon in sediment cores containing live eelgrass Zostera marina plants collected from the Limfjord, Denmark. Detailed temporal and spatial patterns of acetylene reduction were consistent with the hypothesis that heterotrophic n~trogen fixation In the eelgrass rhizosphere is stimulated by organic root exudates denved from plant photosynthesis. Nitrogen fixation activlty was approximately 3 x higher in vegetated than unvegetated sediments, and showed strong seasonal patterns and differences in light-dark incubations that corresponded to variations in plant productivity. Rates in both the light and dark were lowest in the winter months, and increased steadily through the sprlng and summer to a peak actlvity in August that coincided with the maximum eelgrass aboveyround biomass. Light-incubated cores had significantly higher rates (25 to 4 0 ' ' , > ) than those incubated in the dark during the growth season, and this difference was greatest during the summer months when plant productivity was highest. Nitrogen fixat~on activ~i y aiso snowed strong (5-ioidj spatial vanation with depth in the eelgrass root zone, with highest rates corresponding to the largest root+rhizome biomass and correlating with seasonal changes in belowground biomass distribution. Additions of glucose or NH,' showed that the nitrogen-fixing bacteria were llnuted by organic substrate and were not sensitive to NH,+ concentrations. Molybdate additions indicated that sulfate reducers were responsible for about 25% of the nitrogen fixation activity in the eelgrass rhizosphere. Overall, daily nitrogen fixation rates integrated to a depth of 14 cm in the sediment (1 to 6 mg N m-' d.') were comparable to rates measured in other temperate seagrass meadows, but were lower than those determined for troplcal seagrass beds

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Section: Methodsmentioning

confidence: 69%

Section: Methodsmentioning

confidence: 99%

Temporal and spatial variation in nitrogen fixation activity in the eelgrass Zostera marina rhizosphere

McGlathery¹,

Risgaard-Petersen²,

Christensen³

1998

Mar. Ecol. Prog. Ser.

113

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“…For example, in freshwater lakes the ratio of acetylene reduced to dinitrogen fixed can vary between 2.1:1 to 11.9:1 (Howarth et al, 1988). Ideally, future studies should cross-calibrate the acetylene reduction method with the 15 N tracer method (Seitzinger and Garber, 1987). Second, it is possible that the rates of acetylene reduction were not linear over the 24 h of incubation, although previous acetylene assay incubations using similar Arctic glacier cryoconite have been shown to be linear over this timescale (Telling , 2011).…”

Section: Active Nitrogen Fixation In the Marginal And Glacier Zonesmentioning

confidence: 99%

Microbial nitrogen cycling on the Greenland Ice Sheet

et al. 2012

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Abstract. Nitrogen inputs and microbial nitrogen cycling were investigated along a 79 km transect into the Greenland Ice Sheet (GrIS) during the main ablation season in summer 2010. The depletion of dissolved nitrate and production of ammonium (relative to icemelt) in cryoconite holes on Leverett Glacier, within 7.5 km of the ice sheet margin, suggested microbial uptake and ammonification respectively. Positive in situ acetylene assays indicated nitrogen fixation both in a debris-rich 100 m marginal zone and up to 5.7 km upslope on Leverett Glacier (with rates up to 16.3 µmoles C 2 H 4 m −2 day −1 ). No positive acetylene assays were detected > 5.7 km into the ablation zone of the ice sheet. Potential nitrogen fixation only occurred when concentrations of dissolved and sediment-bound inorganic nitrogen were undetectable. Estimates of nitrogen fluxes onto the transect suggest that nitrogen fixation is likely of minor importance to the overall nitrogen budget of Leverett Glacier and of negligible importance to the nitrogen budget on the main ice sheet itself. Nitrogen fixation is however potentially important as a source of nitrogen to microbial communities in the debrisrich marginal zone close to the terminus of the glacier, where nitrogen fixation may aid the colonization of subglacial and moraine-derived debris.

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“…For scaling purposes, the halved sub-core samples were summed and extrapolated to area units using the aperture of the core. Rates of sediment acetylene reduction were scaled to fixed N 2 (as NH 4 + ) using a 3:1 molar conversion (Seitzinger & Garber 1987). An initial analysis to determine the potential for autotrophic sediment N 2 fixation in vegetated sediments showed no differences within a 2 × 2 design for oxic versus anoxic and light versus dark incubation (F = 1.76, p = 0.2), with all rates comparable to N 2 fixation rates in dark anoxic sediment.…”

Section: N 2 Fixationmentioning

confidence: 99%

“…Incubations lasted for 4 to 6 h, and were ended by shaking the bottle vigorously for 30 s, waiting 10 s to allow bubbles trapping gases to dissolve, and then the headspace was drawn into a pre-evacuated vacutainer using a double-ended needle for storage until it was run on the gas chromatograph. As for the sediments, rates of epiphyte acetylene reduction were scaled to fixed N 2 (as NH 4 + ) using a 3:1 molar conversion (Seitzinger & Garber 1987). The fixed N 2 was representative of the leaf area of the top 15 cm of the leaves incubated.…”

Section: N 2 Fixationmentioning

confidence: 99%

Nitrogen fixation in restored eelgrass meadows

Cole¹,

McGlathery²

2012

Mar. Ecol. Prog. Ser.

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Biological nitrogen (N 2 ) fixation is the primary input of new nitrogen (N) to marine systems, and is important in meeting the N demands of primary producers. In this study, we determined whether restoration of the eelgrass Zostera marina L. in a shallow coastal bay facilitated increasing rates of N 2 fixation as the meadows aged. Rates of N 2 fixation were measured in a system that had been devoid of eelgrass following local extinction in the 1930s until restoration by seeding began in 2001. Restored meadows of different ages were compared to nearby bare sediment sites during summer peak metabolism over 2 yr. Nutrient addition by N 2 fixation was enhanced as the meadows aged. Rates of N 2 fixation in the older (7 to 8 yr old) meadows were 2.7 times more than the younger (2 to 3 yr old) meadows (average 390 and 146 µmol N m ). Heterotrophic epiphyte bacteria fixed approximately 90% of the total N 2 in Z. marina meadows of both age classes. Both sediment and epiphyte N 2 fixation were strongly related to Z. marina density and sediment organic content, suggesting that shoot density increases the positive feedback of plant presence on N 2 fixation through the release of organic carbon exudates into the rhizosphere and phyllosphere, and the build up of sediment organic matter also increases. The N provided through fixation represented a large fraction (20.5 to 30%) of the total N demand to support eelgrass aboveground growth during this period of peak summertime production.

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Nitrogen fixation and 15N2 calibration of the acetylene reduction assay in coastal marine sediments

Cited by 80 publications

References 27 publications

Temporal and spatial variation in nitrogen fixation activity in the eelgrass Zostera marina rhizosphere

Temporal and spatial variation in nitrogen fixation activity in the eelgrass Zostera marina rhizosphere

Microbial nitrogen cycling on the Greenland Ice Sheet

Nitrogen fixation in restored eelgrass meadows

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