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Type II Aerobic Methane Oxidizing Bacteria (AMOB) Drive Methane Oxidation in Pulsed Wetlands as Indicated by 13C-Phospholipid
Fatty Acid CompositionTaniya Roy Chowdhury*a and Richard P. Dicka
aSchool of Environment & Natural Resources, The Ohio State University, Columbus, OH, U.S.A.
THE OLENTANGY RIVER “Kidney” WETLANDS, Ohio, U.S.A.Soil Sampling Locations (Fig. 3) and Factors:
Factor Number NameLandscape 2 ORW1,ORW2Hydrology 3 Permanently Flooded (PF)
Intermittently Flooded (IF)Upland (UP)
Flow zones 2 Inflow (I), Outflow (O)
Soil Depth 2 0-8 cm816 cm
Season 4 Fall, Winter, Spring, Summer
Soils Incubated under two different concentrations of 13CH4 : 2ppmv and 60ppmv
RESULTS: Potential Methane Oxidation
The magnitude of climate change predicted for the United States over the next 100 years will cause significant impacts on temperature and precipitation patterns
Wetlands are a major source (~25 %) of methane globally1
Aerobic Methane Oxidizing Bacteria (AMOB) have the unique ability to utilize CH4 as the sole source of carbon and energy by the Methane Mono Oxygenase (MMO) mediated reaction
A variety of environmental determinants have been implicated in the dominance of AMOB type. Generally, type I AMOB outcompete type II AMOB in low CH4 (~2ppmv), high oxygen environments, while type II AMOB are favored in high CH4 (≥40ppmv) environments2
AMOB are active at the oxic sediment - water interface (“pulsing fringe”, Fig. 2)
AMOB consume ~30 Tg-CH4-yr-1, and potentially can offset CH4losses to the atmosphere1
Very little is known about the effects of pulsing hydrology and season on the AMOB ecology
Therefore, the Objectives of this Study were:
Experiment 1:Determine the effects of Season and Landscape position on Potential Methane Oxidation (PMO) in the two wetlands
Experiment 2:Determine the effects of Season and Landscape position on the Aerobic Methane Oxidizing Bacteria (AMOB) as reflected by their biomarker Phospholipid Fatty Acid (PLFA) Compositions
INTRODUCTION
WETLAND HYDROLOGY EXPERIMENT
1. Whalen, S.C. (2005). Environ. Eng. Sc. 22(1):73-922. Hanson, R.S., and Hanson, T.E. (1996). Methanotrophic bacteria.
Microbiol. Rev. 60:439–4713. Jahnke, L. L., R. E. Summons, J. M. Hope, and Des Marais, D.J.
(1999). Geochim. Cosmochim. Acta 63:79-934. Altor, A. E. and Mitsch, W.J.. (2006). Ecological Engineering 28:
224-234.5. Crossman, Z.M., Abraham, F., Evershed, R.P. (2004). Environ.Sc. &
Tech. 38: 359–13676. Maxfield, P. J., E. R. C. Hornibrook and Evershed, R.P. (2006). Appl.
Environ. Microbiol. 72: 3901-3907
Effect of Pulsing on Methane Emission in the Olentangy River Wetlands4 (Altor and Mitsch, 2006)
E
Exposed Average
Inundated Average
Aver
age
Met
hane
Flu
x (m
g C
H4-
cm-2
h-1
)
5
1
Intermittently Flooded(IF) with emergent
macrophytes
Intermittently Flooded (IF)
without emergent
macrophytes
PermanentlyFlooded (PF)
10
• Effect of pulsing onMethane emission in the two 1-ha experimental Olentangy River Wetlands
• Methane fluxes in IF zones of the wetlandswere 30% of those in the PF wetland areas (Fig. 1)
Zone of Anaerobic Methanogenesis
Oxic Sediment-Water-Interface: the “Pulsing” fringeO2O2
Wetland – “Kidney” of the Ecosytems
Methane
Fig. 2. Illustration of the Oxygen rich “pulsing fringe” in a Wetland
O2
Fig.1
Figs. 4 & 5:Seasonal average PMO across landscape positions: PMO in Winter significantly higher than in Summer (p< 0.01)PMO statistically higher at 0-8 cm depth of soil in the PF and
IF sites (p< 0.05)
• Soil samples injected with known concentration of 99.99% pure CH4 gas
• PMO reported innmol-CH4.gdwt.-1Soil.h-1
Measure linear
decrease in CH4
concentrationover time (7h) using GC-FID
CH4CO2
SoilSlurry
Std. CH4
Method 1: Potential Methane Oxidation (PMO), Crossman et al. (2004)
99.99%
13CH4Air
Mixing Chamber13C
H413CH4
PLFA Analysis by GC-c-IRMS
Method 2: 13CH4 Incubation Pulse-Chase Experimental Setup: Stable Isotope Probing of PLFA using GC-c-IRMS, Maxfield et al., 2006
Fingerprint AMOB PLFAs:Type I AMOB: 16:1ω5c, 16:1ω7cType II AMOB:18:1ω7c, 18:1ω9c
18:1ω8c
Soils Incubated under two different concentrations of 13CH4 : 2ppmv and 60ppmv
i. “Type I AMOB”: [CH4 ] 40 ppm
The concentration profiles of AMOB signature PLFAs, as detected by Stable Isotope Probing (SIP) completely corroborates with the Potential Methane Oxidation (PMO) values at all study sites
The highest PMO values in the Permanently Flooded site can be entirely attributed to the AMOB, as reflected by the relative abundance of the signature PLFAs
Type I AMOB are dominant under the oxygen rich conditions in contrast to the Type II that are abundant under submerged conditions
The three hydrologically distinct landscape positions each present characteristic microbial community structure, as evident in this study
ACKNOWLEDGEMENT
Dr. W.J. Mitsch, Director, Wilma H. Schiermeier Olentangy River Wetland Research Park, OSU, Columbus, OH, U.S.A.Dr. Andrea Grottoli, Biogeochemistry Lab, School of Earth Sciences,
OSUDR. Kary Green-Church, Director, Campus Chemical Instrument
Center, Mass Spectrometry & Proteomics Facility, OSU
Fig. 6. Compound-specific carbon isotope values of PLFAs incorporating 13C following incubation of Winter soil samples under Yppmv 13CH4 :
A: 0-8cm, PF Site, 2ppmv B: 0-8cm, IF Site, 2ppmv
C: 0-8cm, PF Site, 60ppmv D: 0-8cm, IFSite, 60ppmv
SUMMARY: AMOB PLFA Conc. & PMO
RESULTS: 13C-Phospholipid Fatty Acids
X
X
X
X
X
X X
N
X
XX
X
Fig. 3
Experimental Wetland 1
Upland (UP)
Permanently Flooded (PF)
Soil Sampling Points
IntermittentlyFlooded (IF)
Outflows
EXPERIMENTAL SITE
METHODS
REFERENCES
CONCLUSIONS
Fig. 7. Mean AMOB PLFA concentration (nmolgdwt.-1soil) and PMO at different Landscape positions in Winter and Summer
18:1ω9c 16:1ω5c
18:1ω7c PMO
Color Legend
UP-(0-8)cm
Winter
0 50 100 150 200
ORW1-I-UP 0-8ORW1-I-UP 9-16
ORW1-I-IF 0-8ORW1-I-IF 9-16ORW1-I-PF 0-8
ORW1-I-PF 9-16
Winter Data
PF-8-16 cm
PF-0-8 cm
IF-8-16 cm
IF-0-8 cm
UP-8-16 cm
UP-0-8 cm
Summer Data
0 20 40 60 80 100
ORW1-I-UP 0-8
ORW1-I-UP 9-16
ORW1-I-IF 0-8
ORW1-I-IF 9-16
ORW1-I-PF 0-8
ORW1-I-PF 9-16Summer Data
PF-8-16 cmPF-0-8 cmIF-8-16 cmIF-0-8 cmUP-8-16 cmUP-0-8 cm
0 20 40 60 80 200
PF-8-16 cm
PF-0-8 cm
IF-8-16 cm
IF-0-8 cm
UP-8-16 cm
UP-0-8 cm
Experimental Wetland 2
Inflows
Nat
ure
Pre
cedi
ngs
: doi
:10.
1038
/npr
e.20
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