scholarly journals A global marine-fixed nitrogen isotopic budget: Implications for Holocene nitrogen cycling

2002 ◽  
Vol 16 (4) ◽  
pp. 67-1-67-14 ◽  
Author(s):  
Jay A. Brandes ◽  
Allan H. Devol
Keyword(s):  
Nitrogen Cycling ◽  
Fixed Nitrogen

scholarly journals Stimulation of microbial nitrogen cycling in aquatic ecosystems by benthic macrofauna: mechanisms and environmental implications

2013 ◽  
Vol 10 (7) ◽  
pp. 11785-11824 ◽  
Author(s):  
P. Stief
Keyword(s):  
Nitrous Oxide ◽  
Nitrogen Cycling ◽  
Nitrogen Removal ◽  
Aquatic Ecosystems ◽  
Ecosystem Engineering ◽  
Benthic Macrofauna ◽  
Published Data ◽  
Fixed Nitrogen ◽  
Environmental Implications ◽  
Microbe Interactions

Abstract. Invertebrate animals that live at the bottom of aquatic ecosystems (i.e., benthic macrofauna) are important mediators between nutrients in the water column and microbes in the benthos. The presence of benthic macrofauna stimulates microbial nutrient dynamics through different types of animal–microbe interactions, which potentially affect the trophic status of aquatic ecosystems. This review contrasts three types of animal–microbe interactions in the benthos of aquatic ecosystems: (i) ecosystem engineering, (ii) grazing, and (iii) symbiosis. Their specific contributions to the turnover of fixed nitrogen (mainly nitrate and ammonium) and the emission of the greenhouse gas nitrous oxide are evaluated. Published data indicate that ecosystem engineering by sediment-burrowing macrofauna stimulates benthic nitrification and denitrification, which together allows fixed nitrogen removal. However, the release of ammonium from sediments often is enhanced even more than the sedimentary uptake of nitrate. Ecosystem engineering by reef-building macrofauna increases nitrogen retention and ammonium concentrations in shallow aquatic ecosystems, but allows organic nitrogen removal through harvesting. Grazing by macrofauna on benthic microbes apparently has small or neutral effects on nitrogen cycling. Animal-microbe symbioses provide abundant and distinct benthic compartments for a multitude of nitrogen-cycle pathways. Recent studies revealed that ecosystem engineering, grazing, and symbioses of benthic macrofauna significantly enhance nitrous oxide emission from shallow aquatic ecosystems. The beneficial effect of benthic macrofauna on fixed nitrogen removal through coupled nitrification–denitrification can thus be offset by the concurrent release of (i) ammonium that stimulates aquatic primary production and (ii) nitrous oxide that contributes to global warming. Overall, benthic macrofauna intensifies the coupling between benthos, pelagial, and atmosphere through enhanced turnover and transport of nitrogen.

scholarly journals Stimulation of microbial nitrogen cycling in aquatic ecosystems by benthic macrofauna: mechanisms and environmental implications

2013 ◽  
Vol 10 (12) ◽  
pp. 7829-7846 ◽  
Author(s):  
P. Stief
Keyword(s):  
Nitrous Oxide ◽  
Nitrogen Cycling ◽  
Nitrogen Removal ◽  
Aquatic Ecosystems ◽  
Ecosystem Engineering ◽  
Benthic Macrofauna ◽  
Published Data ◽  
Fixed Nitrogen ◽  
Environmental Implications ◽  
Microbe Interactions

Abstract. Invertebrate animals that live at the bottom of aquatic ecosystems (i.e., benthic macrofauna) are important mediators between nutrients in the water column and microbes in the benthos. The presence of benthic macrofauna stimulates microbial nutrient dynamics through different types of animal–microbe interactions, which potentially affect the trophic status of aquatic ecosystems. This review contrasts three types of animal–microbe interactions in the benthos of aquatic ecosystems: (i) ecosystem engineering, (ii) grazing, and (iii) symbiosis. Their specific contributions to the turnover of fixed nitrogen (mainly nitrate and ammonium) and the emission of the greenhouse gas nitrous oxide are evaluated. Published data indicate that ecosystem engineering by sediment-burrowing macrofauna stimulates benthic nitrification and denitrification, which together allows fixed nitrogen removal. However, the release of ammonium from sediments is enhanced more strongly than the sedimentary uptake of nitrate. Ecosystem engineering by reef-building macrofauna increases nitrogen retention and ammonium concentrations in shallow aquatic ecosystems, but allows organic nitrogen removal through harvesting. Grazing by macrofauna on benthic microbes apparently has small or neutral effects on nitrogen cycling. Animal–microbe symbioses provide abundant and distinct benthic compartments for a multitude of nitrogen-cycle pathways. Recent studies reveal that ecosystem engineering, grazing, and symbioses of benthic macrofauna significantly enhance nitrous oxide emission from shallow aquatic ecosystems. The beneficial effect of benthic macrofauna on fixed nitrogen removal through coupled nitrification–denitrification can thus be offset by the concurrent release of (i) ammonium that stimulates aquatic primary production and (ii) nitrous oxide that contributes to global warming. Overall, benthic macrofauna intensifies the coupling between benthos, pelagial, and atmosphere through enhanced turnover and transport of nitrogen.

Anthropogenic Impact on Quantitative Differentiation of Nitrogen Cycling Bacteria in Waters of the Drwęca River

2008 ◽  
Vol 23 (3) ◽  
pp. 667-680 ◽  
Author(s):  
Iwona Gołaś ◽  
Izabella Zmysłowska ◽  
Monika Harnisz ◽  
Karol Korzekwa ◽  
Agnieszka Skowrońska ◽  
...  
Keyword(s):  
Nitrogen Cycling ◽  
Anthropogenic Impact

Partitioning of Symbiotically Fixed Nitrogen in Soybeans and Alfalfa 1

Crop Science ◽  
1984 ◽  
Vol 24 (5) ◽  
pp. 986-990 ◽  
Author(s):  
R. A. Henson ◽  
G. H. Heichel
Keyword(s):  
Fixed Nitrogen

Researching nitrogen solubility in nitrogen-containing austenitic steels at melting and recrystallization by CALPHAD method

2019 ◽  
pp. 53-66 ◽  
Author(s):  
L. A. Smirnov ◽  
I. I. Gorbachev ◽  
V. V. Popov ◽  
A. Yu. Pasynkov ◽  
A. S. Oryshchenko ◽  
...  
Keyword(s):  
Global Minimum ◽  
Nitrogen Solubility ◽  
Thermodynamic Description ◽  
Solidus Temperature ◽  
Liquidus Line ◽  
Calphad Method ◽  
Austenitic Steels ◽  
Nitrogen Transfer ◽  
Fixed Nitrogen ◽  
System Phase

The CALPHAD method has been employed to compose thermodynamic description of the Fe–Cr–Mn–Ni–Si–C–N system. Using an algorithm based on finding a global minimum of Gibbs energy, the calculations of system phase composition were performed in the temperature range from 1750°C to hardening and in the range of compositions corresponding to 04Kh20N6G11M2AFB steel. Calculations showed that at temperatures above liquidus line, Cr and Mn increase nitrogen solubility in the melt, while Ni and Si reduce it. With an increase in the content of Cr, Mn, Ni, and Si in steel in the studied composition range, both liquidus and solidus temperature decrease. The degree of influence on these temperatures of Cr, Mn, Ni and Si within the steel grade is different and ranges from ~3 to ~14°C. Calculations taking into account the possibility of nitrogen transfer between steel and the atmosphere of air showed that the amount of fixed nitrogen in the alloy under study varies, depending on the composition of the steel and temperature, from ~0.3 to ~0.6 wt%. As the temperature decreases from liquidus to solidus, the amount of fixed nitrogen increases, with the exception of those steel compositions when ferrite and not austenite is released from the liquid phase.

IMPACTS OF AGRICULTURE ON GREENHOUSE GASES AND NITROGEN CYCLING

2016 ◽  
Author(s):  
Nicole K. Mehr ◽  
◽  
Carol Adair ◽  
Carol Adair ◽  
Lindsay Barbieri ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Nitrogen Cycling
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