Methane emissions along a salt marsh salinity gradient

Bartlett, Karen B.; Bartlett, D. S.; Harriss, Robert C.; Sebacher, Daniel I.

doi:10.1007/bf02187365

Cited by 291 publications

(177 citation statements)

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“…Several of the studies in this review used either transparent or opaque flux chambers, with just three studies that used both. The presence of light can have either large effects (Van der Nat and Middelburg 2000) or negligible effects (Bartlett et al 1987) on methane emission rates, depending on plant community composition. Most studies in this analysis did not account for possible differences in methane emissions in light and dark conditions.…”

Section: Methodsmentioning

confidence: 99%

“…The presence of sulfate in tidal marsh soils allows sulfate-reducing bacteria to outcompete methanogens for energy sources, consequently inhibiting methane production (DeLaune et al 1983, Bartlett et al 1987, Wang et al 1996. This relationship can be complicated by site-specific conditions that may allow methane production in saline marshes to persist despite the inhibitory effects of sulfate (Megonigal et al 2004, Weston et al 2011.…”

Section: Introductionmentioning

confidence: 99%

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Salinity Influence on Methane Emissions from Tidal Marshes

2011

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The relationship between methane emissions and salinity is not well understood in tidal marshes, leading to uncertainty about the net effect of marsh conservation and restoration on greenhouse gas balance. We used published and unpublished field data to investigate the relationships between tidal marsh methane emissions, salinity, and porewater concentrations of methane and sulfate, then used these relationships to consider the balance between methane emissions and soil carbon sequestration. Polyhaline tidal marshes (salinity >18) had significantly lower methane emissions (mean ± sd=1±2 gm −2 yr −1) than other marshes, and can be expected to decrease radiative forcing when created or restored. There was no significant difference in methane emissions from fresh (salinity=0-0.5) and mesohaline (5-18) marshes (42±76 and 16±11 gm −2 yr −1, respectively), while oligohaline (0.5-5) marshes had the highest and most variable methane emissions (150±221 gm −2 yr −1). Annual methane emissions were modeled using a linear fit of salinity against log-transformed methane flux ( logðCH 4 Þ ¼ À0:056 Â salinity þ 1:38; r 2 = 0 . 5 2 ; p < 0.0001). Managers interested in using marshes as greenhouse gas sinks can assume negligible methane emissions in polyhaline systems, but need to estimate or monitor methane emissions in lower-salinity marshes.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Salinity Influence on Methane Emissions from Tidal Marshes

2011

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“…The carbon, hydrologic, and anthropogenic management and plant community dynamics of these water bodies are considered to be distinct from those of natural wetlands. Saline systems, in particular, may involve processes that are missing in freshwater wetland models such as sulphate reduction (Bartlett et al, 1987). In practice however, the models are commonly not able to distinguish between wetlands and these other non-wetland water bodies; thus exclusion of these systems is commonly accomplished through masking of the grid cells with observational datasets (Table A1).…”

Section: Wetland Definitionmentioning

confidence: 99%

Present state of global wetland extent and wetland methane modelling: conclusions from a model inter-comparison project (WETCHIMP)

et al. 2013

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Global wetlands are believed to be climate sensitive, and are the largest natural emitters of methane (CH4). Increased wetland CH4 emissions could act as a positive feedback to future warming. The Wetland and Wetland CH4 Inter-comparison of Models Project (WETCHIMP) investigated our present ability to simulate large-scale wetland characteristics and corresponding CH4 emissions. To ensure inter-comparability, we used a common experimental protocol driving all models with the same climate and carbon dioxide (CO2) forcing datasets. The WETCHIMP experiments were conducted for model equilibrium states as well as transient simulations covering the last century. Sensitivity experiments investigated model response to changes in selected forcing inputs (precipitation, temperature, and atmospheric CO2 concentration). Ten models participated, covering the spectrum from simple to relatively complex, including models tailored either for regional or global simulations. The models also varied in methods to calculate wetland size and location, with some models simulating wetland area prognostically, while other models relied on remotely sensed inundation datasets, or an approach intermediate between the two. Four major conclusions emerged from the project. First, the suite of models demonstrate extensive disagreement in their simulations of wetland areal extent and CH4 emissions, in both space and time. Simple metrics of wetland area, such as the latitudinal gradient, show large variability, principally between models that use inundation dataset information and those that independently determine wetland area. Agreement between the models improves for zonally summed CH4 emissions, but large variation between the models remains. For annual global CH4 emissions, the models vary by ±40% of the all-model mean (190 Tg CH4 yr−1). Second, all models show a strong positive response to increased atmospheric CO2 concentrations (857 ppm) in both CH4 emissions and wetland area. In response to increasing global temperatures (+3.4 °C globally spatially uniform), on average, the models decreased wetland area and CH4 fluxes, primarily in the tropics, but the magnitude and sign of the response varied greatly. Models were least sensitive to increased global precipitation (+3.9 % globally spatially uniform) with a consistent small positive response in CH4 fluxes and wetland area. Results from the 20th century transient simulation show that interactions between climate forcings could have strong non-linear effects. Third, we presently do not have sufficient wetland methane observation datasets adequate to evaluate model fluxes at a spatial scale c...

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“…Many studies have attributed the decrease in wetland CH 4 emissions along increasing salinity and sulfate concentrations to sulfate-reducing bacteria outcompeting methanogens for substrates (DeLaune et al, 1983;Bartlett et al, 1987;Magenheimer et al, 1996;Poffenbarger et al, 2011), but none of these studies directly assessed whether lower CH 4 emissions resulted from reduced CH 4 production or higher CH 4 oxidation. Two recent studies documented lower CH 4 production with elevated salinity (Chambers et al, 2013;Neubauer et al, 2013), and attempted to link C mineralization rates to extracellular enzymes, but microbial communities were not quantified.…”

Section: Non-tidal Freshwater and Tidal Brackish Wetland Comparisonmentioning

confidence: 99%

Regulators of coastal wetland methane production and responses to simulated global change

et al. 2017

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Abstract. Wetlands are the largest natural source of methane (CH 4 ) emissions to the atmosphere, which vary along salinity and productivity gradients. Global change has the potential to reshape these gradients and therefore alter future contributions of wetlands to the global CH 4 budget. Our study examined CH 4 production along a natural salinity gradient in fully inundated coastal Alaska wetlands. In the laboratory, we incubated natural sediments to compare CH 4 production rates between non-tidal freshwater and tidal brackish wetlands, and quantified the abundances of methanogens and sulfate-reducing bacteria in these ecosystems. We also simulated seawater intrusion and enhanced organic matter availability, which we predicted would have contrasting effects on coastal wetland CH 4 production. Tidal brackish wetlands produced less CH 4 than non-tidal freshwater wetlands probably due to high sulfate availability and generally higher abundances of sulfate-reducing bacteria, whereas non-tidal freshwater wetlands had significantly greater methanogen abundances. Seawater addition experiments with freshwater sediments, however, did not reduce CH 4 production, perhaps because the 14-day incubation period was too short to elicit a shift in microbial communities. In contrast, increased organic matter enhanced CH 4 production in 75 % of the incubations, but this response depended on the macrophyte species added, with half of the species treatments having no significant effect. Our study suggests that CH 4 production in coastal wetlands, and therefore their overall contribution to the global CH 4 cycle, will be sensitive to increased organic matter availability and potentially seawater intrusion. To better predict future wetland contributions to the global CH 4 budget, future studies and modeling efforts should investigate how multiple global change mechanisms will interact to impact CH 4 dynamics.

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Methane emissions along a salt marsh salinity gradient

Cited by 291 publications

References 50 publications

Salinity Influence on Methane Emissions from Tidal Marshes

Salinity Influence on Methane Emissions from Tidal Marshes

Present state of global wetland extent and wetland methane modelling: conclusions from a model inter-comparison project (WETCHIMP)

Regulators of coastal wetland methane production and responses to simulated global change

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