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Using 14 C to investigate methane production and DOC reactivity in northern peatlands Liz Corbett*, Jeffrey P. Chanton, Paul A. Glaser, William T. Cooper, Donald I. Siegel, Mimi Sarkar, Julianna D’Andrilli Department of Oceanography, Florida State University, Tallahassee, FL 32306 - PowerPoint PPT Presentation
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Using 14C to investigate methane production and DOC reactivity in northern peatlands
Liz Corbett*, Jeffrey P. Chanton, Paul A. Glaser, William T. Cooper, Donald I. Siegel, Mimi Sarkar, Julianna D’AndrilliDepartment of Oceanography, Florida State University, Tallahassee, FL 32306
*corresponding author: [email protected]
IntroductionPeatlands are a large carbon reservoirs. These ecosystems are saturated with water, and therefore, have an extremely low rate of decomposition. In this way, they have stored and accumulated carbon for over 6,000 years. With the current threat of global warming, they have the potential to become a carbon source to the outside environment by either leaching large amounts of DOC into connecting rivers or by producing CO2 and CH4 into the atmosphere by increased microbial respiration.
Purpose of StudyUnderstand why microbes in a fen environment show a
shift from acetate fermentation to CO2 reduction at depth,
but microbes in a bog environment utilize CO2 reduction
at all depthsQuantify the DOC size reservoirs in the peatland
environmentDifferentiate between bog and fen DOC Differentiate between deep and surface DOCDetermine which DOC sizes serve as a microbial food
sourceCategorize DOC based on size, aromaticity and structure EEMS plots showing UV
degradation as DOC travels downstream
Concentrations of DOC Separated by Size in Surface Fen and Bog
-20
0
20
40
60
80
100
0-1 1--3 3--10 10--100 100+
DOC Size Categories (kDa)
Per
cent
age
for
DO
C T
otal
RL2 Bog sfc
Crest Bog 0.5m
RL2 Fen 20cm
SR Fen 0.5m
Concentrations of DOC Separated by Size in Deep Fen and Bog
-20
0
20
40
60
80
100
0-1 1--3 3--10 10--100 100+
DOC Size Categories (kDa)
Perc
enta
ge o
f Tot
al D
OC
RL2 Bog 3m
Crest Bog 3m
RL2 Fen 2.5m
SR 3m
Size Filtration study showing larger concentrations of LMW DOC suggesting bacterial preferentially choose HMW DOC as a resource and leave behind LMW DOC to accumulate
Microbes seem to prefer fen DOC to bog DOC since the 14C value of their respiration products (CO2 and CH4) exactly matches DOC in the fen environments, but only partly matches bog DOC.
0
0.5
1
1.5
2
2.5
3
-400 -200 0 200
14C ‰
Dept
h (m
)
Peat
DOCDIC & CH4
BOG
0
0.5
1
1.5
2
2.5
3
-400 -200 0 200
14C ‰
Dept
h (m
)
Peat
DOC, DIC & CH4
FEN
2007 Bog and Fen C:N Ratio (corrected for ammonium and NOx)
0
1
2
3
4
5
-600.0 -400.0 -200.0 0.0 200.0 400.0 600.0
C:N
Dept
h (m
)
Lawn
LRB
RL2 Bog
RL2 Fen
WWT
Fen DOC has a lower C:N ratio meaning it is more labile and a better food source for the bacterial community
2008 Bog and Fen C:N Comparision (corrected for ammonium and NOx)
0
1
2
3
4
5
-600 -400 -200 0 200 400 600
C:N
Dep
th (m
)
RLIV Bog
SR Bog
RidgeBogFBc
RL4 Fen
SR Fen
ConclusionsData suggests that the structure or quality of DOC may differ
between the bog and fen environmentsFen DOC is more labile than bog DOC suggesting it as a better
food source for bacteriaThe concentration of LMW DOC increases with depth
suggesting LMW accumulates because it is not utilized by
bacteria, whereas HMW concentrations increase as the bacteria
metabolize it as a food sourceDOC degradation by UV light suggests that the DOC is made
up of aromatic groupsThe cross-plot shows a shift in metabolic pathways in the fen but
not in the bog
Cross-plot shows the transition from aceticlastic methanogenesis to CO2 reduction that the bacteria make in the fen with depth, but the constant use of the CO2 reduction at all depths occurs in the bogs