Presentation is loading. Please wait.

Presentation is loading. Please wait.

New Stable Isotopic Tools for the Marine Nitrogen Cycle

Published byEdward Leonard Modified over 5 years ago

Similar presentations

Presentation on theme: "New Stable Isotopic Tools for the Marine Nitrogen Cycle"— Presentation transcript:

1 New Stable Isotopic Tools for the Marine Nitrogen Cycle
Karen L. Casciotti WHOI, Department of Marine Chemistry and Geochemistry

2 Biogeochemical cycles of C, N, P
The fact is that a lot of important nutrient cycles are driven biologically…well, there are important bio/physical/chemical coupling… We need to understand how these processes interact and affect each other. Gruber and Galloway 2008 Nature 451:

3 Increasing Greenhouse Gas Levels
Atmospheric CO2 at Mauna Loa Observatory AGAGE Atmospheric N2O records N2O has 300x global warming potential per mole than CO2

4 Oxygen Deficient Zones
ETNP Oxygen (mL/L) at 250 m Arabian Sea ETSP Suboxic regions have long been recognized as important regions of the world’s oceans, although our understanding of the N cycle in these regions has undergone substantial change in the past 5-10 years WOA05 data plotted in ODV Highly productive Sources of N2O Response to anthropogenic activity--expansion/intensification Quantitative importance in marine nitrogen budget

5 Suboxic Nitrogen Cycle
N2, N2O Particulate NO3- Surface ocean N DON, NH3 Deep ocean N2 upwelling Anammox Remineralization NH3 NO2- NO3- Nitrification NO Major questions… N2 fixation in overlying waters? Anammox vs. denitrification? who is oxidizing ammonium? Denitrification N2O Burial N2 Major questions…

6 What role can a microbiologist play in understanding global biogeochemistry?

7 Stable Isotopes of NO3-, NO2-, and N2O
in Air N2 d15N (‰) = [(15N/14Nsample / 15N/14NAIR) -1 ] *1000 16O: % 17O: % 18O: % in Standard Mean Ocean Water d18O (‰) = [(18O/16Osample / 18O/16OSMOW) -1 ] *1000

8 The Denitrifier Method: Simultaneous N and O Isotopic Analyses
Pseudomonas aureofaciens or Pseudomonas chlororaphis Inject NO3- or NO2- sample Denitrification takes place NO3- NO2- NO N2O N2 N2O (g) Analyze N2O isotopes Sigman et al., Analytical Chemistry: 15N-NO3- Casciotti et al., Analytical Chemistry: 18O-NO3-

9 Peru Upwelling: d15NO3- 19 18 17 10 16 11 12 15 10 11 12 13 14 16 17 19 13 14

10 Rayleigh Model for Isotope Fractionation in a Closed System
d15NH4+ (substrate) d15NO2- (instantaneous product) d15Nsubstrate ≈ d15Ninitial substrate - e * ln(f) e d15NO2- (accumulated product) e BEGINNING d15Naccumulated product ≈ d15Ninitial substrate + e * f ln(f)/(1-f) END

11 Linearized Rayleigh Model
Substrate Product Substrate f*ln(f)/(1-f) d15N Product e d15N e -ln(f) f = the fraction of initial substrate remaining

12 Casciotti and Voytek, unpublished Phylogeny of June
Ammonia monooxygenase Clones from Sugar Creek, Indiana Stream nitrifier community 67 = 14.2 ± 0.5‰ Casciotti and Voytek, unpublished Nitrosospira tenuis 98 79 = 24.6 ± 1.4‰ 90 60 91 81 Nitrosomonas marina = 14.2 ± 3.6‰ Nitrosomonas sp. C-113a 74 = 19.1 ± 1.2‰ 72 Nitrosomonas eutropha 96 = 32.8 ± 1.7‰ 100 Nitrosomonas europaea = 38.2 ± 1.6‰ 98

13 Important to know who is there and who is active
Potential for variability in isotope effects within a ‘functional group’ Important to know who is there and who is active

14 Stable Isotope Fractionation at the Cell Level
Nitrifier cell periplasm Transport? NH4+ NH4+ expt eeq eeq cytoplasm ediff eamo ehao NH3 NH3 NH2OH NO2- NO2- ediff Diffusion eoverall is dominated by ediff Without transport With transport eoverall is dominated by expt

15 Potential for variability within a given species
Important to know physiological factors that may play a role

16 d15N variations in NO3- 20 Water column denitrification e  20-30 ‰ 15
d15NO3- (‰ vs. AIR) Nitrate assimilation e  5-10 ‰ 10 Nitrogen fixation d15N  0 ‰ 5 Sedimentary denitrification e  0 ‰ 0.5 1 1.5 2 [NO3-]/[NO3-]initial Sigman and Casciotti, 2001 EOS

17 d15N variations in NO3- d15NNO3 d15NNO3 N2 Fixation Low d15N Depth (m) High d15NO3- Depth (m) Denitrification Arabian Sea ETNP d15NN2 d15NN2 Brandes et al. (1998) L&O Gross rates of nitrogen fixation and denitrification are difficult to diagnose.

18 Coupled d15N and d18O analyses of nitrate
N isotopes O isotopes Nitrogen fixation N2 Denitrification N2 Denitrification Norg Norg Assimilation Assimilation NO3- NO3- Nitrification Not going to have time to talk about nitrification/oxygen isotope work, but it goes here… Nitrification NH4+ NH4+ O2, H2O

19 Coupled N and O isotopes of NO3-
20 15 (‰ vs. VSMOW) d18O-NO3- 10 Denitrification 15e/ 18e  1 (Granger et al., 2006) Nitrate assimilation 15e/ 18e  1 5 (Granger et al., 2004) Deep Ocean 5 10 15 20 d15N-NO3- (‰ vs. AIR)

20 Coupled N and O isotopes of NO3-
20 15 (‰ vs. VSMOW) d18O-NO3- 10 5 Remineralization/Nitrification 5 10 15 20 d15N-NO3- (‰ vs. AIR)

21 Coupled N and O isotopes of NO3-
20 15 (‰ vs. VSMOW) d18O-NO3- 10 N2 fixation/ Nitrification D(15,18) 5 Remineralization/Nitrification 5 10 15 20 d15N-NO3- (‰ vs. AIR) D(15,18) = (d15N - d15Ndeep) - 15e/18e * (d18O - d18Odeep) Sigman et al., 2005

22 Coupled N and O isotopes of NO3-
20 15 (‰ vs. VSMOW) d18O-NO3- 10 N2 fixation/ Nitrification D(15,18) 5 Remineralization/Nitrification 5 10 15 20 d15N-NO3- (‰ vs. AIR) D(15,18) = (d15N - d15Ndeep) - 15e/18e * (d18O - d18Odeep) Sigman et al., 2005

23 Nitrate d15N and d18O deviations
20 N2 Fixation Low d15N Remineralized PN from Nitrogen fixation 15 Nitrite reoxidation High d15NO3- d18O-NO3- (‰ vs. VSMOW) 10 Nitrite reoxidation Denitrification Denitrification 15e/ 18e  1 5 5 10 15 20 NO NO2- N2 d15N-NO3- (‰ vs. AIR) D(15,18) = (d15N - d15Ndeep) - 15e/18e * (d18O - d18Odeep) Sigman et al., 2005

24 ETNP NO3- isotope studies
Map from Cline and Kaplan, 1975 Sigman et al > 65% of Denitrified N is replaced by nitrification of newly fixed N. Brandes et al. 1998 Cline and Kaplan 1975 This study Voss et al. 2001 Sutka et al., 2004 Sigman et al. 2003, 2005 Altabet et al., 1999

25 The Denitrifier Method: Simultaneous N and O Isotopic Analyses
Pseudomonas aureofaciens or Pseudomonas chlororaphis Inject NO3- or NO2- sample Denitrification takes place NO3- NO2- NO N2O N2 N2O (g) Analyze N2O isotopes Sigman et al., Analytical Chemistry: 15N-NO3- Casciotti et al., Analytical Chemistry: 18O-NO3-

26 The Denitrifier Method: Simultaneous N and O Isotopic Analyses
Pseudomonas aureofaciens or Pseudomonas chlororaphis Inject NO3- or NO2- sample Denitrification takes place NO3- NO2- NO N2O N2 Granger et al., 2006 N2O (g) Analyze N2O isotopes Sigman et al., Analytical Chemistry: 15N-NO3- Casciotti et al., Analytical Chemistry: 18O-NO3-

27 Nitrite isotope subtraction
Pretreatment Ascorbate NO2- Isotopic analysis Denitrifier Azide Denitrifier d15N, d18O (NO3- + NO2-) d15N, d18O (NO2-) d15N, d18O (NO3-) 2 Subtract d15N, d18O (NO3-) 1 Compare

28 ETNP Nitrate Isotope Data
d15N d18O Casciotti and McIlvin, 2007 Marine Chemistry

29 ETNP Nitrate and Nitrite Isotopes
d15N (‰), D(15,18) (‰), and [NO2-] (mM) d15NNO3 d15NNO2+NO3 d15NNO2 D(15,18) D(15,18) = (d15N - d15Ndeep) - 15e/18e * (d18O - d18Odeep) Casciotti and McIlvin, 2007 Marine Chemistry

30 ETNP Nitrate and Nitrite Isotopes
d15N (‰), D(15,18) (‰), and [NO2-] (mM) d15NNO3 d15NNO2+NO3 d15NNO2 D(15,18) Casciotti and McIlvin, 2007 Marine Chemistry

31 Model Interpretation of D(15,18)
20 Mixing with shallower water Remineralized PN from Nitrogen fixation 15 of diazotroph biomass Remineralization d18O-NO3- (‰ vs. VSMOW) Nitrate reduction Denitrification (or Anammox) 10 Nitrite reoxidation NO3- NO2- Denitrification 15e/ 18e  1 Nitrite “reoxidation” 5 Mixing with deeper water 5 10 15 20 d15N-NO3- (‰ vs. AIR) Based on Sigman et al model

32 Model Results NO NO2- N2 Casciotti and McIlvin, 2007 Marine Chemistry

33 ETNP Nitrate and Nitrite Isotopes
d15N (‰), D(15,18) (‰), and [NO2-] (mM) d15NNO3 d15NNO2+NO3 d15NNO2 Nitrite reoxidation at top of omz could be…0.6 umol m-2 d-1 D(15,18) Nitrite reoxidation going on…additional information needed

34 Nitrite Oxidation in the ETSP
Nitrite oxidation rate nmol/L/day [NO2-] mmol/L Lipschultz et al., 1990: Showed nitrite oxidation below SNM and associated w/PNM but little at the top of the OMZ in the ETSP Nitrate reduction rate nmol/L/day [O2] mmol/L

35 ETNP Samples d15N (‰), D(15,18) (‰), and [NO2-] (mM) d15NNO3
d15NNO2+NO3 d15NNO2 D(15,18)

36 Isotope effects for nitrite reactions
d15N Nitrite oxidation 15eNO 15eNR NO3- NO2- d15N Nitrate reduction Initial condition NO3- 15eNR NO3- NO2- NO2- N2 15eNIR Initial condition Nitrate reduction Nitrite reduction

37 Nitrite reduction by (de)nitrifying bacteria
14NO NO 15NO NO Casciotti, Sigman, and Ward, unpublished

38 Isotope effects for nitrite reactions
d15N Nitrite oxidation 15eNO 15eNR NO3- NO2- d15N Nitrate reduction Initial condition NO3- 15eNR NO3- NO2- NO2- 15eNIR N2 Initial condition Nitrate reduction Nitrite reduction

39 Nitrite oxidation by Nitrococcus mobilis
NO2- NO3- “Inverse isotope effect” 14NO NO3- d15NNO3 15NO NO3- d15NNO2

40 Isotope effects for nitrite reactions
d15N d15N NO3- NO3- NO3- 15eNR 15eNR NO3- NO3- NO2- NO3- NO2- 15eNIR NO2- 15eNO NO2- N2 Initial condition Nitrate reduction Nitrite reduction Initial condition Nitrate reduction Nitrite oxidation

41 ETNP Samples d15N (‰), D(15,18) (‰), and [NO2-] (mM)

42 Implications for interpretation of D(15,18)
Now required nitrite oxidation rate less than 0.9 mM/yr and oxidation/reduction ratio ~0.7 Can’t rule out a contribution from N2 fixation, but… Many indicators consistent with nitrite oxidation: Location of D(15,18) minimum Low nitrite d15N Large nitrate/nitrite d15N offset Inverse isotope effect for nitrite oxidation Strength of D(15,18) minimum

43 Implications for interpretation of D(15,18)
Now required nitrite oxidation rate less than 0.9 mM/yr and oxidation/reduction ratio ~0.7 Can’t rule out a contribution from N2 fixation, but… Many indicators consistent with nitrite oxidation: Location of D(15,18) minimum Low nitrite d15N Large nitrate/nitrite d15N offset Inverse isotope effect for nitrite oxidation Strength of D(15,18) minimum

44 Suboxic Nitrogen Cycle
N2, N2O Particulate NO3- Surface ocean N DON, NH3 Deep ocean N2 upwelling Anammox Remineralization NH3 NO2- NO3- Nitrification NO Major questions… N2 fixation in overlying waters? Anammox vs. denitrification? who is oxidizing ammonium? Denitrification N2O Burial N2

45 Ongoing and Future Work
Oxygen isotopic systematics of ammonia oxidation Nitrogen and oxygen isotopic systematics of nitrite oxidation Interpret coupled N and O isotopic signatures from nitrate and nitrite using more sophisticated models Extend analysis to additional ODZs (Arabian Sea; Benguela; GEOTRACES)

46 Acknowledgements Matthew McIlvin Danny Sigman ETNP work Carrie Tuit
Penzance Assistant Scientist Endowed Support NSF Chemical Oceanography Nitrite Oxidizer work Carly Buchwald

Download ppt "New Stable Isotopic Tools for the Marine Nitrogen Cycle"

Similar presentations

What is the Nitrogen cycle The nitrogen cycle is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen- containing compounds.

What is the Nitrogen cycle The nitrogen cycle is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen- containing compounds.
NITROGEN CYCLE. Nitro Composes about four-fifths (78.03 percent) by volume of the atmosphere an essential part of the amino acids. It is a basic element.

NITROGEN CYCLE. Nitro Composes about four-fifths (78.03 percent) by volume of the atmosphere an essential part of the amino acids. It is a basic element.
Effect of surfactants on N 2 O emissions from biologically productive regions Annette Kock, Jens Schafstall, Tim Fischer, Marcus Dengler, Peter Brandt.

Effect of surfactants on N 2 O emissions from biologically productive regions Annette Kock, Jens Schafstall, Tim Fischer, Marcus Dengler, Peter Brandt.
Chris Gammons, John Babcock, Bev Plumb, Steve Parker Montana Tech, Butte, MT Spatial and temporal variations in nutrient concentration and speciation in.

Chris Gammons, John Babcock, Bev Plumb, Steve Parker Montana Tech, Butte, MT Spatial and temporal variations in nutrient concentration and speciation in.
Lecture 19 The Ocean Nitrogen Cycle Sinks/Sources Sink - Denitrification Reactions Distributions Source - Nitrogen Fixation Reactions Distributions The.

Lecture 19 The Ocean Nitrogen Cycle Sinks/Sources Sink - Denitrification Reactions Distributions Source - Nitrogen Fixation Reactions Distributions The.
Conversion of organic nitrogen into N 2 in the oceans: where does it happen? and how? Yuan-Hui (Telu) Li Department of Oceanography University of Hawaii.

Conversion of organic nitrogen into N 2 in the oceans: where does it happen? and how? Yuan-Hui (Telu) Li Department of Oceanography University of Hawaii.
Nitrogen Isotopes & the biological pump11/8/12 Lecture outline: 1)the nitrogen cycle  15 N overview 3)ocean applications 4)the sedimentary record A.

Nitrogen Isotopes & the biological pump11/8/12 Lecture outline: 1)the nitrogen cycle  15 N overview 3)ocean applications 4)the sedimentary record A.
1 Nitrogen Cycle Most of Nitrogen is in the atmosphere. 14 N = 99.6% 15 N = 0.4% Air is standard for  15 N Range is –20 to +20 ‰

1 Nitrogen Cycle Most of Nitrogen is in the atmosphere. 14 N = 99.6% 15 N = 0.4% Air is standard for  15 N Range is –20 to +20 ‰
Marine Nitrogen Cycle Matthieu Heine. Marine Nitrogen Cycle Global patterns of marine nitrogen fixation and denitrification. Nicolas Gruber and Jorge.

Marine Nitrogen Cycle Matthieu Heine. Marine Nitrogen Cycle Global patterns of marine nitrogen fixation and denitrification. Nicolas Gruber and Jorge.
NITROGEN CYCLE. Wikipedia.org Nitrogen Fixation N 2 NH 4 +

NITROGEN CYCLE. Wikipedia.org Nitrogen Fixation N 2 NH 4 +
Nitrate isotopes as a constraint on the ocean's fixed N budget Angela Knapp, University of Southern California Peter DiFiore, Princeton University Curtis.

Nitrate isotopes as a constraint on the ocean's fixed N budget Angela Knapp, University of Southern California Peter DiFiore, Princeton University Curtis.
Nitrate Dynamics at ALOHA and K2 Karen Casciotti Woods Hole Oceanographic Institution Department of Marine Chemistry and Geochemistry.

Nitrate Dynamics at ALOHA and K2 Karen Casciotti Woods Hole Oceanographic Institution Department of Marine Chemistry and Geochemistry.
UK GEOTRACES: Characterizing nitrate isotopes in South Atlantic water masses (40°S). UK GEOTRACES: Characterizing nitrate isotopes in South Atlantic water.

UK GEOTRACES: Characterizing nitrate isotopes in South Atlantic water masses (40°S). UK GEOTRACES: Characterizing nitrate isotopes in South Atlantic water.
GEOF236 CHEMICAL OCEANOGRAPHY (HØST 2012) Christoph Heinze University of Bergen, Geophysical Institute and Bjerknes Centre for Climate Research Prof. in.

GEOF236 CHEMICAL OCEANOGRAPHY (HØST 2012) Christoph Heinze University of Bergen, Geophysical Institute and Bjerknes Centre for Climate Research Prof. in.
15 N in marine plants Modified by Angela Quiros. (Montoya 2007) There is lots of variation in the 15 N values in the world’s oceans.

15 N in marine plants Modified by Angela Quiros. (Montoya 2007) There is lots of variation in the 15 N values in the world’s oceans.
15 N in marine plants Alison Collins. Major Inputs of Nitrogen in the Ocean 1. Deep Water Nitrate 2.Atmospheric deposition Largest in areas near continental.

15 N in marine plants Alison Collins. Major Inputs of Nitrogen in the Ocean 1. Deep Water Nitrate 2.Atmospheric deposition Largest in areas near continental.
Lecture 18 The Ocean Nitrogen Cycle Denitrification Reactions Distributions Nitrogen Fixation Reactions Distributions.

Lecture 18 The Ocean Nitrogen Cycle Denitrification Reactions Distributions Nitrogen Fixation Reactions Distributions.
OS13B - 0536 Modeling the Distribution and  15 N of Nitrogen Gas and Nitrogen Species in the Black Sea S. K. Konovalov 1, C. A. Fuchsman 2 and J.W. Murray.

OS13B Modeling the Distribution and  15 N of Nitrogen Gas and Nitrogen Species in the Black Sea S. K. Konovalov 1, C. A. Fuchsman 2 and J.W. Murray.
The nitrogen cycle is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen- containing compounds in nature biogeochemical.

The nitrogen cycle is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen- containing compounds in nature biogeochemical.
Marine Geochemistry 2 Reference: Schulz and Zabel Marine Geochemistry Springer, New York 2000 453 pp. ISBN 3-540-66-453-X.

Marine Geochemistry 2 Reference: Schulz and Zabel Marine Geochemistry Springer, New York pp. ISBN X.

Similar presentations

Ads by Google