Salt Marsh Restoration: Changes in Greenhouse Gas Flux
Nia Bartolucci
50 College Street
South Hadley, MA, 01075
Mentor: Dr. Jim Tang
Ecosystem Center
7 MBL Street
Marine Biological Laboratories, Woods Hole, MA 02543
December 20, 2015
1
Abstract:
In this project a 2 week lab experiment was designed to test how the restoration of
Herring river, a fresh marsh that was a salt marsh before the diking of the Herring River system
in the early 1900s, would affect greenhouse gas flux (CH4 and CO2). Sediment cores were taken
at Herring River and a salt marsh, Stony Brook, and then treated with either fresh or salt water.
CH4 and CO2 fluxes from the cores were then measured five days a week for a 2 week period.
Although there wasn’t a statistical effect of the different water treatments on CH4 flux, general
trends showed that the addition of salt water decreased CH4 flux while the addition of fresh water
increased CH4 flux. CO2 emissions were lower in the controls and higher in cores treated with
the opposite water type than their natural conditions. Field measurements of CH4 and CO2
emissions were also taken at three restored salt marshes to see how length of time since
restoration affects greenhouse gas flux. Due to the cold weather, the data from this portion of the
experiment is inconclusive.
Key words: Salt marsh, greenhouse gas flux, restoration, Herring River, methane, carbon dioxide
Introduction:
Salt marshes are among the most productive systems in the world (Kennish, 2001,
Broome et al 1987). Coastal salt marshes carry out many vital ecosystem functions such as
filtration of coastal runoff, flood abatement, habitat for many plant and animal species and
carbon sequestration. Although many of the functions of salt marshes have been studied
extensively, one function that is not well understood and needs further study is the capability of
salt marshes to offset and help mitigate the amount of greenhouse gases in the atmosphere
through their ability to sequester and store carbon (Tang, 2015).
With rising CO2 levels from primarily anthropogenic causes now at 398.2 ppm, and the
effects of climate change already altering and affecting the world, there have been efforts to
research the capability of natural ecosystem to store carbon (ESRL NOAA 2015). This idea of
using natural ecosystem to help decrease CO2 levels is called “blue carbon” and is a relatively
new area of study (Mcleod, 2011). According to Mcleod et al. (2011), coastal salt marshes store
40 times more carbon then forested upland areas and therefore have been and continue to be
systems that are studied for their carbon storage capacity.
One effect of climate change that is starting to affect salt marshes and greenhouse gas
flux from these systems is sea level rise (Waquoit Bay National Estuarine Research Reserve
2012). According to research done by the Waquoit Bay National Estuarine Research Reserve
2
(2012), carbon burial has increased from 50-100 g C m-2 yr-1 in 1900 to 75 – 250 g C m-2 yr-1;
This can be attributed to sea level rise which has created more marsh area and has allowed for
more C to be stored. However, in order for carbon to be optimally stored with rising sea level,
elevation growth must keep up with sea level rise (Weston et al 2011). As we start to see
increased sea level rise, it is apparent that we will start to see shifts in salt marsh conditions that
will effect biogeochemical processes that lead to greenhouse gas emissions (Helton et al 2014).
While there is some knowledge about the conditions that lead to burial of C or emissions of
greenhouse gases, there is still much that remains unknown.
Biogeochemical processes in salt marshes
Biogeochemical and microbial processes largely control the emissions of both CH4 and
CO2 in salt marshes. While there are several different types of microbial metabolism, two
processes that occur and have the most relevance in regards to this project are sulfate reduction
and methanogenesis. Through the process of methanogenesis, CH4, a green house gas that has 25
times the global warming potential of CO2, is emitted (Howarth, 2011). CH4 flux is significantly
affected by the water table, as methanogenesis is an anaerobic process (Moore and Knowles
1989). Methanogenesis is the metabolic activity of microbes known as methanogens. Through
the reduction of CO2 or the fermentation of acetate, CH2 is produced (Valiela 1995). CH4 is
released into the atmosphere through one of three processes: ebullition, diffusion or arrenchyma
(Mitsch and Gosselink 2007). Ebullition is when gases rise to the surface trapped in bubbles,
diffusion is when gas is dispersed through the water column, and arrenchyma is the transport of
gases through the vascular systems of plants (Mitsch and Gosselink 2007).
The microbial metabolism that dominates salt marshes however is sulfate reduction
(Valiela 1995). This can be attributed to the absence of other more favorable electrons acceptors
such as oxygen, nitrate, manganese, and ferric iron. Sulfate reduction inhibits methanogenesis in
three ways. Firstly sulfate reduction yields more energy for sulfate reducing bacteria, which
allows them to outcompete methanogens which use less preferential electron acceptors (Valiela
1995). Secondly, sulfate reducers also oxidize CH4, which further decreases CH4 flux, and lastly,
the reduction of sulfate to sulfide prevents methanogenesis (Valiela 1995). Poffenbarger et al.
(2011) found that CH4 emissions are considerably less in salt marshes in comparison with fresh
water wetlands because of the high concentrations of SO42- in salt water.
3
Methanogenesis: CH3COO- +4 H2 = 2 CH4 + 2H2O
CH3COO- = CH4 + CO2b
Sulfate reduction: CH3COO- + SO4= = 2 CO2 +2 H2O
SO42- + 4H2 = 2H2O +HS(Equations taken from Valiela 1995)
Salt marshes provide short-term storage of C through biomass of vegetation, and provide
long-term storage through their capacity to store C in anaerobic sediments (Mcleod, 2011).
However, although salt marshes are net carbon sinks, they also emit CO2 as salt marshes
experience periodic oxidation which allows for aerobic decomposition of organic material which
then results in emission of CO2. (Moseman- Valtierra, 2011) Moore and Knowles (1989) found
that CO2 emissions were greatly impacted by the level of inundation; completely flooded cores
had much lower emissions than partially flooded cores. Also, another source of CO2 emission
from salt marshes is autotrophic and heterotrophic respiration.
Historically, salt marshes in the New England area were destroyed through dredging and
diking to create agricultural land as well as drained areas for development (Kennish, 2001)
(Bertness et al, 2002). As these sites were diked and drained and became oxidized upland
systems, they lost many of their original ecological functions such as their capacity to store
carbon. As the value of these ecosystems is being discovered and the need to find solutions to
deal with ever-rising CO2 levels in the atmosphere, there have been efforts to restore many of
these coastal wetlands.
In my project, I explored this function of salt marshes as emitters of greenhouse gases in
various New England salt marshes. I also studied how restoration of a salt marsh affects
greenhouse gas flux, specifically CO2 and CH4 flux. To better understand how restoration affects
greenhouse gas emissions I set up a series of sediment core incubations and treated them with
either salt or fresh water to simulate the placement or removal of a dike. I also took in field
measurements at four different locations on Cape Cod, Massachusetts. For my lab experiment, I
predict that the saltwater sediment cores will have lower CH4 flux than the freshwater cores due
to high concentrations of SO4-2 in the salt water. For the treated cores, I hypothesize that the fresh
cores treated with salt water will have greater CH4 flux than the saltmarsh cores treated with
fresh water because I predict that there will higher sulfate concentrations in the saltmarsh core
4
treated with salt water than the freshwater core treated with fresh water. For the in field
measurements, I hypothesize that the fluxes of both CO2 and CH4 will decrease with length of
time since restoration. The following report documents my two and half week experiment that
sought to address these topics.
Methods:
Site Descriptions (see appendix for map):
Stony Brook (41 45.275'N 70 6.767'W): Stony Brook is located in Brewster, MA. The site is
dominated by Spartina spp. It was the most recently restored site of the salt marshes studied in
this experiment; it was restored in 2010.
Herring River (41.96058N, 70.05587W): The Herring River site is located in Wellfleet, MA.
The Herring River site was originally a salt marsh but after the insertion of a dike in the early
1900s has becomes a fresh marsh as tidal inundation has been restricted. The site is dominated
by Typha species.
Quivett Creek (41 44.813'N 70 8.614'W): Quivett Creek is a salt marsh that is located in
Dennis, MA. It was restored in 2005. The vegetation is primarily Spartina spp
Chequessett (41.930457N, 70.071033W): Chequessett is located in Wellfleet, MA. It is located
at the mouth of the Herring River site. The site is also dominated by Spartina spp.
Core Collection
We collected 16 approximately 50 cm sediment cores on November 17th, 2015 from two
different locations, 8 from Stony Brook, a salt marsh and 8 from Herring River, a fresh marsh. At
the Stony Brook site, we took the cores from the southwestern portion of the salt marsh near to
where Dr. Tang previously established sampling site. At the Herring River sites, we took the
cores adjacent to another established sampling area located close to the road in the southeastern
portion of the marsh.
We collected the cores by pounding polyvinyl cores into the ground using a
sledgehammer. Once the cores were completely driven into the ground, a metal fitting was
fastened around the next of the core and attached to a sawhorse cradle with a crank mechanism
attached. Before removing the cores from the ground, we pushed a rubber plug into the cores to
create a vacuum to keep the sediment in the core. Once we removed the cores from the ground,
we capped them with plastic caps to transport back to the lab.
5
Lab Experiment Set Up and Maintenance
The incubation treatments were set up on November 18th, 2015. We drilled holes in the
bottom caps and fit them with ports so that pore water could be sampled. To minimize leaking
for when we flooded the cores, we wrapped the bottom part of the core where the end of the cap
met the core with ½ inch thread sealing tape to ensure the cap had a snug fit. We also sealed the
remaining gap between the cap and the core with ¾ inch black electrical tape, and then lastly fit a
metal collar around the core.
We collected a carboy of seawater from the Marine Biological docks in Woods Hole, MA
and then filtered it using 25mm GF/F swinex filters. The 16 cores were treated with different
types of water, and were set up in replicates of 4. We flooded four of the cores from Stony Brook
with saltwater while the remaining four cores were flooded with DI water. The same treatments
were applied to the Herring River cores; four were flooded with DI water and four were flooded
with salt water. The Herring River cores with DI water and the Stony Brook cores with salt water
acted as controls and represented what happens naturally. The Stony Brook cores with the fresh
water simulated the diking of the system while the Herring River cores with added salt water
simulate the restoration of a salt marsh by the removal of the dike and the return of tidal flow.
Because the different cores varied in depth, differential amounts of water were added to the
cores. Water was added until the entirety of the sediment was submerged in water. The cores
were left open and were stored in a controlled environment with an ambient temperature of
approximately 21 degrees C.
Field Measurements:
We took field measurements using the Picarro CO2, CH4, and H2O gas analyzer. We took
measurements at the Herring River and Chequessett site on Nov. 24th, 2015. The field data for
Stony Brook and Quivette Creek was collected on Dec. 3rd, 2015. Field conditions and
temperature were comparable between these different dates.
Greenhouse Gas Measurements and Flux Calculations
I took greenhouse gas measurements using the G2301 Picarro CO2, CH4, and H2O gas
analyzer ( Picarro Inc. Santa Clara, CA, USA). For the lab experiment, I took samples
6
approximately five days a week for a two-week incubation period. Once concentrations were
recorded using the Picarro gas analyzer, fluxes were calculated using the computer program
Matlab 6 (Mathworks, Natick, MA, USA).
Physical Parameters, DOC and Sulfate Analysis:
I collected pore water from the cores on Nov. 18, 2015, Nov. 19th, 2015, Nov. 23rd, 2015, and
Nov. 30th, 2015. At each pore water collection time, I also measured pH, temperature, redox, and
salinity using Spectrum FieldScout SoilStik electrode meters. The pore water was then filtered
through 47mm GF/D filter followed by a 47mm GF/F filter. Once filtered, dissolved organic
carbon (DOC) samples were acidified with 1 μliter of phosphoric acid for each mL of sample.
Samples were run on the total organic carbon analyzer (OL Analytical Aurora 1030). Sulfate
concentrations were determined using the Dionex, ion chromatograph.
Statistical Analysis:
I used the StatPlus add-on for Microsoft Excel 2011 and SPSS21.0 to run one-way and
two-way ANOVAs to determine significant effects and interactions between the field sites and
different treatments in the lab experiment. A 95% confidence interval was used to determine
significance.
Results:
Lab Experiment:
CH4 fluxes from the incubated sediment cores show no clear trends in any of the
treatments before and at the beginning of the incubation (Figure 1). The fresh marsh core treated
with salt water (FS) has a large peak at day zero and the salt marsh core with salt water (SS) had
a large dip at day one (Figure 1). However, towards the end of the incubation, the fluxes begin to
become steadier and show that the controls show discernable differences in fluxes; the fresh
marsh core with fresh water (FF) has higher CH4 flux than the salt marsh core treated with salt
water (Figure 1). The salt marsh core with fresh waster (SF) and the fresh marsh core with salt
water (FS) do not show clear trends (Figure 1). The results of a two-way ANOVA show that
neither the origin of the sediment core (p=0.36), treatment (either fresh water or salt water)
(p=0.90), nor the combination of the two (p= 0.53) have a significant effect on the CH4 flux
(df=13). However, general trends in the data suggest that the addition of fresh water to the salt
7
marsh cores increases the CH4 flux while the addition of salt water to the fresh water cores
decreases CH4 flux (Figure 2).
CO2 fluxes from the incubation experiment show extremely high fluxes at the beginning
of the incubation period but then quickly decrease in all treatments in the subsequent days
(Figure 3). Again the trends between the different treatments don’t show any clear trends (Figure
3). Statistical analysis of the mean fluxes over the incubation period, conclude that there is not an
effect of origin (p=0.67) on the sediment core or the treatment of the cores (p=0.73) on CO2 flux
(df= 14). However the interaction of both treatment and origin did have a significant affect on
CO2 flux (df= 14, p= 0.48). Adding fresh water to the salt-water cores increased CO2 flux as did
adding salt water to the fresh water cores (Figure 4). Comparing CO2 flux with CH4 flux across
the different treatments, CO2 had substantially higher fluxes than CH4 ( Figure 2, Figure 4).
Physical Parameters, Sulfate, and DOC Analysis:
pH was highest in the SF cores (7.15), followed by the SS cores (6.88), then the FF cores
(5.59), and lastly the FS cores (4.99) ( Figure 5). pH data across the incubation period show
general increase in pH in all cores expect the FS treatment (Figure 6).
Average redox of the different treatments follow the same patterns as the pH data (Figure
7). Over the incubation period, the redox values became less negative in the SF and SS cores
(Figure 8). The FF and FS cores start out with positive values but then become negative with
time, and then increase towards the end of the incubation period (Figure 8). The data from Nov.
19 shows opposite trends from what was observed in the other days, and shows large positive
values for all the treatments (Figure 8). In calculating mean values, the data from Nov. 19 was
excluded.
Salinity was highest in the SS cores (24ppm), followed by the SF cores (21 ppm), then
the FS cores (4 ppm), and lastly the FF cores (<1 ppm) (Table 1).
Sulfate data mostly correlates with the pH and redox data; average concentrations are
highest in the SS cores (12,313 μmols/L), followed by the SF cores (8,625 μmols /L), then FS
cores (3,619 μmols /L), and lastly FF cores (732 μmols /L (Figure 9). Average dissolved organic
carbon (DOC) was highest in the FS cores (179.30 ppm), lowest in the SS cores (31.95 ppm) and
intermediary in the FF and SF cores (98.56 ppm) (31.78ppm) respectively (Figure 10).
8
Field Measurements
CH4 flux was highest at the Herring River site (0.0104 μmols m-2 sec-1 ) , followed by
Quivette Creek (0.0102 μmols m-2 sec-1 ), then Stony Brook (0.0035 μmols m-2 sec-1 ), then
Chequessett (9.5x10-5 ) (Figure 11). The standard error for Quivette Creek indicates much greater
variance for this site( Figure 11). Using a one way ANOVA to compare the different sites show
that there wasn’t a statistical effect of site on CH4 flux ( df= 19, p=0.051). CO2 flux was highest
at the Quivette Creek (0.4999 μmols m-2 sec-1) and lowest at Stony Brook (-0.213 μmols m-2 sec1
) (Figure 12). Herring River and Chequesset had intermediary CO2 flux (0.0802 μmols m-2 sec-1
) (-0.0087 μmols m-2 sec-1 ) respectively (Figure 12). The results of a one way ANOVA show
that there is no statistical effect of the site on the CO2 flux (df=29, p=0.42). Similarly to the lab
experiment, CO2 fluxes were higher than CH4 fluxes ( Figure 2, Figure 4, Figure 11, Figure 12)
Discussion:
Lab Experiment:
Although there weren’t any significant effects of the origin, treatment, or origin and
treatment in combination on CH4 flux from the lab experiment cores, the general trends that we
observed are what we expected. CH4 flux was highest in the cores in which fresh water was
added. Salt water has high concentrations of SO4-2. This presence of SO4-2, which is a
preferential electron acceptor allow sulfate reduction to be the dominant process and inhibit
methanogenesis. CH4 increased in the cores where we added fresh water because SO42concentrations were lower; this is corroborated by the SO42- concentration data. These results are
comparable to those of Poffenberger et al (2011) who found decreasing CH4 with increasing
salinity and SO4-2 concentrations.
CO2 fluxes from the sediment cores showed that the addition of fresh or salt water to
either the fresh marsh or salt marsh core had a significant effect on CO2 flux. The addition of
fresh water to the salt marsh could have increased CO2 flux because the fresh water could have
allowed microbes that were once limited by high salinity to become more active which increased
their respiration. The higher CO2 flux in the SF cores could be attributed to more living roots in
the cores; the salt marsh cores overall still had many residual root systems in the cores which
could elevate CO2 flux. Higher CO2 flux from the fresh marsh treated with salt water could also
be attributed to high sulfate concentrations which then accelerated decomposition of soil organic
9
matter. This is supported by high DOC in the pore water that was collected from the FS cores.
However, it is predicted that this is short -term trend and that over time as the added salt water
causes an increase in salinity microbes would eventually become limited.
Physical Parameters and SO42- data
The salt marsh cores had the highest pH and the largest negative redox values. This is due
to the high rates of dissimilatory sulfate reduction that reduces SO42- to H2S. This process
consumes H ions, which then results in a higher pH. Also high negative redox values are
expected with high concentrations of H2S. However, the data from Nov. 19 displays redox
results that are inconsistent with the general trends from the rest of the data. This dissimilar data
is most likely explained by the fact that the cores were flooded on this date. The immediate
flooding and disruption of what was happening naturally, resulted in peaked results. The high pH
correlates with low CH4 emissions due to the presence of SO4-2 which t allows sulfate reduction
to be the dominate process and out compete methanogens.
Field Measurements
The field measurements show much higher CO2 flux than CH4 flux. This is expected, as
CH4 release into the atmosphere is much smaller than total soil respiration. CH4 is highest in the
fresh marsh, Herring River, and lowest in the natural salt marsh, Chequessett. This can be
explained by high SO42- in the salt marsh and low SO42- in the fresh marsh. The high CH4
emissions in the Quivette Creek contradict what is expected. As Quivette Creek was restored ten
years ago, I expected Quivette Creek to have lower flux than the Stony Brook salt marsh that was
restored more recently. I also expected to see more of a difference between the Herring River site
and the salt marsh sites. It may be that since Herring River was a natural salt marsh that was
then diked in the early 1900s that there is residual SO42- in the sediments that then inhibits
methanogenesis. Also, there are such large error bars in the Quivette Creek site, that a larger
sample number is needed to get accurate results.
10
Conclusion:
One thing to consider about this experiment was the brevity of it. Looking at the
greenhouse gas fluxes from the sediment cores across the sampling time, it becomes evident that
it takes time for fluxes to normalize from the disturbance of being removed from the
environment and then flooded. For example, the CO2 fluxes start off very high from all the
treatments, this is due to the oxidation of the sediment core that occurred during the transport and
set up of the experiment and doesn’t represent normal fluxes. In order to get more realistic fluxes
it would be necessary to have a much longer incubation period.
For the field experiment, it was hard to discern any significant trends largely because of
the time of the year I took measurements. I sampled in late November to early December after
the days have become colder compared to summer months and many of the plants have senesced
and microbial activity has decreased. As microbial activities largely influence greenhouse gas
emission, their decreased activity significantly decreases CH4 and CO2 efflux. It would be
interesting to continue to measure CO2 and CH4 throughout the year to see how fluxes change
throughout the year. Also, since fluxes are dependent on many factors it is hard to get an
accurate understanding of fluxes from one day of measurements. In conclusion, with the affects
of climate change already impacting the globe, it is important that studies similar to this one
continue so that we can better understand the intricacies and conditions that lead to greenhouse
gas emissions from natural ecosystems.
Acknowledgements:
Thank you to my mentor Jim Tang who helped me with experimental design. Joanna Carey for
her insights and help explaining the biogeochemistry of wetlands. To Thomas Parker for his help
with statistics and to Liz de la Reguera for showing me around the lab and her general support.
Thank you to Rich Mchorney for helping me with DOC and sulfate analysis. Thank you to the
wonderful TAs – Brecia, Hannah, and Aliza, for their input and their direction in lab. Special
thanks to Faming Wang who helped me with every step of my project from data collection to
explaining the results we found. I could not have done this project without his guidance. Lastly,
thank you to Olivia Box and Erica Moretti for their input, support, and laughter throughout the
whole process.
11
Literature Cited:
Bertness, M, P. Ewanchuk, and B. Silliman. 2002. Anthropogenic modification of New
England salt marsh landscapes. Proceedings of the National Academy of Sciences of
the United States of America. 99(3): 1395-1398
Broome, S., E. Seneca, E. Woodhouse. 1988. “Tidal salt marsh restoration” Aquatic Botany.
32(1-2): 1-22
ESRL/NOAA (Earth Systems Research Laboratory/National Oceanic and Atmospheric
Administration). 2015. http://www.esrl.noaa.gov/gmd/ccgg/trends/. Viewed 9
November, 2015.
Helton, A., E. Bernhardt, A. Fedders. 2014.”Biogeochemical regime shifts in coastal landscapes:
the contrasting effects of saltwater incursion and agricultural pollution on greenhouse gas
emissions from a freshwater wetland.” Biogeochemistry. 120:133-147
Howarth, R.W. 2011. “Methane and the greenhouse gas footprint of natural gas from shale
formations” Climatic Change. Vol 106(4):679-690
Kennish, M. 2001. “Coastal salt marsh systems in the U.S: a review of anthropogenic impacts.”
Journal of Coastal Research 17(3):731-748
Mcleod E. G. Chmura, S. Bouillon, R. Salm, M. Bjork, C.M. Duarte, C.E. Lovelock, W.H.
Schlesinger, B.R. Silliman. 2011. “A blueprint for blue carbon: toward an improved
understanding of the role of vegetated coastal habitats in sequestering CO2” Frontiers in
Ecology and the Environment. 9(10): 552-560
Mitsch, W.J and J.G Gosselink. 2007. Wetlands. Hoboken, New Jersey. John Wiley and Sons
Inc.
Moore, T, R. Knowles. 1989. “The Influence of Water Table Levels on Methane an Carbon
Dioxide Emissions from Peatlands Soils” Canadian Journal of Soil Science.” 69(1): 3338
Moseman-Valteierra, S, R. Gonzales, K. Kroeger, J. Tang, W. Chao, J. Crusius, J. Bratton, A.
Green, J. Shelton. 2011. Atmospheric Environment. 45(26): 4390-4397
Poffenbarger H. B. Needelman, J. Megonigal. “salinity influence on methane emissions from
tidal marshes.” Wetlands. 31(5):831-842
Tang, Jim. 2015. Personal Communication.
Valiela, I. 1995.Marine Ecological Processes. Springer Science and Business Media, Inc. New
York, New York, USA
12
Waquoit Bay National Estuarine Research Reserve. 2012. “ Greenhouse gas fluxes and carbon
storage in wetlands: summary of BWM science findings” Fact Sheet.
Weston, N.B, M.A. Vile, S.C. Neubauer, D.J, Velinsky. 2011. “Accelerated microbial organic
matter mineralization following salt-water intrusion into tidal freshwater marsh soils.”
Biogeochemistry. 102:135-151
13
Tables and Figures list:
Table 1: Average salinity of the different cores
Figure 1: CH4 flux of the different core treatments over the incubation period
Figure 2: Average CH4 flux of the different core treatments
Figure 3: CO2 flux of the different core treatments over the incubation period
Figure 4: Average CO2 flux of the different core treatments
Figure 5: Average pH of the different core treatments
Figure 6: pH of the different core treatments over time.
Figure 7: Average redox values (mv) of the different core treatments
Figure 8: Redox values of the different core treatments over time
Figure 9: Sulfate concentrations of the different core treatments.
Figure 10: Dissolved organic carbon (DOC) of the different core treatments.
Figure 11: Methane emissions from the different field sites
Figure 12: CO2 emissions from the different field sites
14
Tables and Figures:
Table 1: Average salinity (ppm) of the individual sediment cores
Origin
Treatment
Salinity (ppm)
F
F
0
F
F
0
F
F
0
F
F
0
F
S
2
F
S
5
F
S
6
F
S
2
S
S
22
S
S
25
S
S
24
S
S
24
S
F
20
S
F
21
S
F
25
S
F
19
15
.0300
μmol m-2 sec-1
.0200
Fresh Marsh with Fresh Water
.0100
Fresh Marsh with Salt Water
.0000
Salt Marsh with Fresh Water
-1
0
0.5
1
3
4
6
-.0100
-.0200
8
10
11
Salt Marsh with Salt Water
Days After Incubation
Figure 1: Average CH4 flux (μmols m-2 sec-1) from the different core treatments over the
incubation period.
16
0.006
umol m-2 sec-1
0.005
0.004
add salt
0.003
add fresh
0.002
0.001
0
Salt Marsh
Fresh Marsh
Figure 2: Average CH4 flux (μmols m-2 sec-1) of the different core treatments from day 3-11 of
the incubation period. Error bars display standard error.
17
20
umol m-2 sec-1
15
10
FF
FS
5
SF
SS
0
-1
0
0.5
1
3
4
6
8
10
11
-5
-10
Days After Incubation
Figure 3: CO2 flux (μmols m-2 sec-1) from the different core treatments over the incubation
period.
18
2
μmol m-2 sec-1
1.5
1
add salt
add fresh
0.5
0
Salt Marsh
Fresh Marsh
-0.5
Figure 4: Average CO2 flux (μmols m-2 sec-1) of the different core treatments from day 3-11 of
the incubation period. Error bars display standard error.
19
8
7
6
pH
5
4
3
2
1
0
Fresh Marsh Fresh
Water
Fresh Marsh Salt
Water
Salt Marsh Salt
Water
Salt Marsh Fresh
Water
Figure 5: Average pH of the different core treatments. Error bars display standard error.
20
8
7
pH
6
5
Fresh Marsh Fresh Water
4
Fresh Marsh Salt Water
3
Salt Marsh Salt Water
Salt Marsh Fresh Water
2
1
0
18-Nov
19-Nov
23-Nov
30-Nov
Figure 6: pH of the different core treatments over time. Error bars display standard error.
21
50
0
-50
Fresh Marsh
Fresh Water
Fresh Marsh Salt Salt Marsh Salt Salt Marsh Fresh
Water
Water
Water
mV
-100
-150
-200
-250
-300
-350
Figure 7: Average redox values (mv) of the different core treatments. Error bars display standard
error
22
400
300
200
Fresh Marsh Fresh Water
mV
100
Fresh Marsh Salt Water
0
18-Nov
-100
19-Nov
23-Nov
30-Nov
Salt Marsh Salt Water
Salt Marsh Fresh Water
-200
-300
-400
Figure 8: Redox values (mV) of the different core treatments over time. Error bars display
standard error.
23
20000
μmol
16000
12000
8000
4000
0
Fresh Marsh Fresh
Water
Fresh Marsh Salt WaterSalt Marsh Fresh Water Salt Marsh Salt Water
Figure 9: Sulfate concentrations (μmol) of the different core treatments. Error bars display
standard error.
24
300
250
ppm
200
150
100
50
0
Fresh Marsh Fresh
Water
Fresh Marsh Salt
Water
Salt Marsh Fresh
Water
Salt Marsh Salt Water
Figure 10: Dissolved organic carbon (DOC) of the different core treatments. Error bars display
standard error.
25
0.025
μmol m--2 sec-1
0.02
0.015
0.01
0.005
0
-0.005
Herring River Fresh
Marsh
Stony Brook 2010
Quivette Creek 2005
Chequessett Natural
Salt Marsh
Figure 11: Methane emissions (μmols m--2 sec-1 ) from the different field sites. Error bars display
standard error.
26
0.8
0.6
μmol m--2 sec-1
0.4
0.2
0
-0.2
Herring River Fresh Stony Brook 2010 Quivette Creek 2005 Chequessett Natural
Marsh
Salt Marsh
-0.4
-0.6
-0.8
Figure 12: CO2 emissions (μmols m--2 sec-1) from the different field sites. Error bars display
standard error.
27
Appendix:
Map of sampling sites
28