Transcript Document

Fig. 1. A generalized biosphere model showing the basic inputs and outputs of energy and materials
P. G. Falkowski et al., Science 320, 1034 -1039 (2008)
Published by AAAS
O2-mediated
Mn -mediated
Fe-mediated
S-mediated
N-mediated
H2 or C-mediated
Mn2+
NH4+
Fe2+
HS-
CH4
H2
[CH2O]
Respiration
O2
Mn4+
NO3N2
N2-fixation
Fe3+
SO42CO2
H2O
+CO2
Photosynthesis
The rise of oxygen altered
the N cycle- The BIG FLIP
• Oxygen permitted NH4 to be converted
to NO3 – which can be rapidly reduced
to N2.
• There was a critical time in Earth’s
history when the N cycle was a major
barrier to oxidizing the planet
• Once over that “hump” we entered a
new stable state.
10
25
5
0
0
-25
-5
-50
-10
0
1
2
3
4
 33
 S
34
50
5
Age (Ga)
d34S sulfate
d34S sulfide
D33S
Courtesy of Farquhar et al, Science 2004
After Jenkyns et al. (2002)
Similar feedback during Oceanic Anoxic Events?
Anoxic environments:
 denitrification
 removal of fixed nitrogen from the ocean
 retards of primary production, favors N2-fixers
Jenkyns et al. 2001
Quan et al., Global Biogeochem Cycles, in press
Is there evidence in the paleorecord?
40
Papineau et al., 20
minus high T
Hayes kerogen
30
Jia Kerrich kerogen
20

Agouron GKP kero
Atlantic bulk
10
Exmouth Plateau bu
Fire Creek bulk
0
Rove/Gunflint bulk
-10
0
1
2
3
Age (Ga)
4
5
Godfrey and Falkowski, in press
Evidence of lateral gene transfer of nif genes
Shi and Falkowski, PNAS 2008
O2-mediated
Mn -mediated
Fe-mediated
S-mediated
N-mediated
H2 or C-mediated
Mn2+
NH4+
Fe2+
HS-
CH4
H2
[CH2O]
Respiration
O2
Mn4+
NO3N2
N2-fixation
Fe3+
SO42CO2
H2O
+CO2
Photosynthesis
Falkowski, Fenchel and Delong, Science, 2008