Methane and Carbon Dioxide Production Rates in Lake Sediments from Sub-Arctic Sweden
Joel DeStasio1, Madison Halloran2, Lance Erickson3, Ruth K Varner4, Joel E Johnson5, Jacob Setera5, Maria F Meana Prado5, Martin Wik6, Patrick M Crill6
1. Departments of Natural Resources and the Environment and Earth Sciences, University of New Hampshire, Durham, NH, United States. 2. Department of Environmental Studies, Carleton College, Northfield, MN, United States. 3.
Department of Geology, Gustavus Adolphus College, St. Peter, MN, United States. 4. Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH, United States.5. Department of Earth Sciences,
University of New Hampshire, Durham, NH, United States. 6. Department of Geological Studies, Stockholm University, Stockholm, Sweden.
Results
• Ecosystems at high latitudes are undergoing rapid change due to amplified atmospheric warming. Lakes in these regions
are sources of both methane (CH4) and carbon dioxide (CO2) to the atmosphere and will likely be impacted by elevated
temperatures.
Villasjön CO2 incubations at 5C
0
Hypotheses
1.2
1.4
0
0.1
0.6
0.7
y = 14.578x + 4.7052
R² = 0.5426
45
40
35
VI1_23cm
VI1_38cm
VI2_4cm
VI2_24cm
VI1_23cm
VI1_38cm
30
25
20C
5C
20
Linear (5C)
15
VI2_4cm
10
5
VI2_24cm
-1
VI2_39cm
Figure 3: CO2 flux rates for samples taken at eastern & western most points of
transect VM. Samples taken from Villasjön.
Villasjön CH4 incubations at 5C
Villasjön CH4 incubations at 20C
0
1
2
3
4
5
6
7
8
0
VI1_8cm
VI1_8cm
VI1_25cm
VI1_25cm
VI1_40cm
VI2_6cm
VI2_26cm
VI2_41cm
Villasjön
1.5
2
2.5
3
Figure 4: CO2 vs. TOC weight % from samples taken from cores VI1 and VI2.
Samples taken from Villasjön.
TOC Content vs. Sediment Depth in Villasjön
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
VI1_40cm
VI2_6cm
VI2_26cm
Figure 6: CO2 flux rates for samples taken at eastern & western most points of
transect VM. Samples taken from Villasjön.
CH4 Concentrations in Villasjon, VP Transect
μg CH4
20
40
g-1
CH4 Concentrations in Villasjon, VM Transect
60
80
100
0
20
40
60
80
Figure 7: Total organic carbon (TOC) content for VM & VP transect core
samples. Samples taken from Villasjön.
Inre Harrsjön & Mellan Harrsjön CH4 Concentrations
μg CH4 g-1ds
ds
0
Photo courtesy of Google Maps,
2013
1
VI2_41cm
Figure 5: CO2 flux rates for samples taken at eastern & western most points of
transect VM. Samples taken from Villasjön.
0
0.5
μg CH4 g-1ds day-1
Core/Sediment Depth (cm)
Core/Sediment Depth (cm)
Mellan Harrsjön
0
μmol CO2 g-1ds day-1
Figure 2: CO2 flux rates for samples taken at eastern & western most points of
transect VM. Samples taken from Villasjön.
Inre Harrsjön
-0.5
VI2_39cm
μg CH4 g-1ds day-1
μg CH4 g-1ds
100
0
0
50
100
150
200
250
300
350
0
5
10
Inre Harrsjön & Mellan Harrsjön (Sites MD1, MS1, ID1 & IS1):
15
VP1
VP2
30
VP3
VP4
VP5
40
VP6
50
60
• 2 sets of samples were taken from each lake; Inre Harrsjön (IS1 &ID1) & Mellan Harrsjön (MS1 & MD1).
Each sample set consisted of 4 individual sediment cores:
- The first core was sub-sampled for CH4 incubation . Duplicate 2 cm3 sub-samples from this core were
taken at surface, middle and maximum sediment depths.
- The second core was sub-sampled for bulk CH4 concentration in increments of 5cm along the length of
the core. Samples were stored in sealed 30mL vials.
Sediment Depth (cm)
20
20
25
30
20
VM1
VM2
VM3
VM4
VM5
VM6
VM4*
35
40
45
Sediment Depth (cm)
Methods
• Cores were taken along 2 perpendicular transects within Villasjön: VM & VP. 2 sediment cores were
taken at each sample site in Villasjön. Cores were sampled for CH4 concentrations, TOC, S, N & C.
Additional sediment cores were also taken from each end of the VM1 transect (VI1 and VI2) for CO2 and
CH4 production rate analysis.
10
10
Sediment Depth (cm)
Villasjön (VM Transect):
0.8
VI1_6cm
• CH4 and CO2 concentrations and production rates will be highest in organic rich sediments containing the highest TOC .
Research site:
50
μmol CO2 g-1ds day-1
0.3
0.4
0.5
0.2
Villasjön CO2 Production vs. TOC
0
•Sediments from areas within Villasjön known to have the highest rates of CH4 ebullition (western end of VM transect) will
yield the highest CH4 concentrations and production rates.
Figure 1 (Right):
Stordalen Mire
complex. The 2
uppermost lakes are
Inre Harrsjön and
Mellan Harrsjön.
Villasjön is the largest
of the three lakes,
located at the bottom
right. The marked
points indicate where
each sample core set
was taken.
1
Core/Sediment Depth (cm)
• Sediment cores were incubated to determine CO2 and CH4 production rates and were analyzed for CH4 concentrations,
dissolved inorganic carbon (DIC) concentrations, total organic carbon (TOC) concentrations, as well as carbon, nitrogen
and sulfur content.
0.4
VI1_6cm
Core/Sediment Depth (cm)
• CH4 and CO2 production potential of sediments were studied using cores from three lakes in the Stordalen Mire complex
in sub-Arctic, Sweden: Inre Harrsjön, Mellan Harrsjön, and Villasjön.
0.2
μmol CO2 g-1ds day-1
0.6
0.8
Villasjön CO2 incubations at 20C
TOC Weight %
Introduction
30
Inre Deep
Inre Shallow
40
Mellan Deep
Mellan Shallow
50
60
50
70
80
Figure 8: CH4 concentrations vs. sediment depth along VP transect.
Samples taken from Villasjön.
55
60
Figure 9: CH4 concentrations vs. sediment depth along VM transect.
Samples taken from Villasjön.
70
80
Figure 10: CH4 concentrations per sediment depth from cores ID1, IS1, MD1 &MS1.
Samples taken from Inre Harrsjön & Mellan Harrsjön.
Conclusions and Future Work
• Villasjön cores indicate that CH4 production rates were highest at the same sediment depths as peak dissolved CH4 concentrations, with maximum values between depths of
approximately 10cm and 30cm (Figures 5,6,8 & 9).
• CH4 production was highest in areas of Villasjön known to have the highest rates of CH4 ebullition.
- The third core was sub-sampled for bulk total
organic carbon (TOC), carbon, sulfur and nitrogen
concentrations in increments of cm along the length of
the core.
• CO2 production was highest in surface sediments ranging from about 4cm to 11cm in depth, with rates displaying a steady decrease below 11cm (Figures 2 & 3).
• CO2 production correlated with total organic carbon (TOC) concentrations with respect to sediment depth. (Figures 2-4 & 7).
• Future isotopic analysis of sediment & headspace samples will help determine if the ages between sampled CH4 and sediment match or differ. Older CH4 would indicate
production may be occurring at depths below what we have sampled.
- The fourth core was sub-sampled every 5cm using
Rhizons to extract pore water samples for dissolved
inorganic carbon (DIC) content.
Acknowledgements
Special thanks to Mr. Dana Hamel, Dr. and Mrs. Arthur G. Rand, Georgeann Murphy, Peter Akerman, ANS and the Northern Ecosystems Research for Undergraduates program (NSF REU site EAR#1063037) for
making this project possible. Additional thanks to my research mentors, Dr. Ruth Varner and Dr. Joel Johnson
Photo: Ruth Varner