Seasonal variations of methane fluxes from an unvegetated tidal freshwater mudflat (Hammersmith Creek, GA)

Segarra, Katherine Eowyn; Samarkin, V.; King, Elizabeth G.; Meile, Christof; Joye, Samantha B.

doi:10.1007/s10533-013-9840-6

Cited by 18 publications

(15 citation statements)

References 58 publications

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“…Considerable reservoirs of porewater methane were present in these FWW pore fluids, all of which supported high rates of biological methane production 21 (Table 1). The anoxic, permanently water-saturated surface soils (see Methods) exhibited the highest rates of AOM ( Fig.…”

Section: Resultsmentioning

confidence: 88%

“…2). Additional methane to support the measured oxidation rates may have been produced from alternative substrates 38 and/or supplied via vertical advection from depths 440 cm or lateral advection 21 in the tidally-influenced sites (Georgia and Florida).…”

Section: Resultsmentioning

confidence: 99%

“…Limiting the comparison to temperate wetlands 60 (0.6-1.1 Â 10 12 m 2 ), AOM may consume between 20 and 40 Tg methane per year, or 1-30 times the estimated annual methane flux from these environments 60,61 . In a direct comparison, atmospheric methane flux measurements 21 were roughly twice the magnitude of areally-integrated AOM rates in Georgia in August 2008.…”

Section: Discussionmentioning

confidence: 97%

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High rates of anaerobic methane oxidation in freshwater wetlands reduce potential atmospheric methane emissions

et al. 2015

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The role of anaerobic oxidation of methane (AOM) in wetlands, the largest natural source of atmospheric methane, is poorly constrained. Here we report rates of microbially mediated AOM (average rate ¼ 20 nmol cm À 3 per day) in three freshwater wetlands that span multiple biogeographical provinces. The observed AOM rates rival those in marine environments. Most AOM activity may have been coupled to sulphate reduction, but other electron acceptors remain feasible. Lipid biomarkers typically associated with anaerobic methane-oxidizing archaea were more enriched in 13 C than those characteristic of marine systems, potentially due to distinct microbial metabolic pathways or dilution with heterotrophic isotope signals. On the basis of this extensive data set, AOM in freshwater wetlands may consume 200 Tg methane per year, reducing their potential methane emissions by over 50%. These findings challenge precepts surrounding wetland carbon cycling and demonstrate the environmental relevance of an anaerobic methane sink in ecosystems traditionally considered strong methane sources.

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Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 97%

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High rates of anaerobic methane oxidation in freshwater wetlands reduce potential atmospheric methane emissions

et al. 2015

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“…Due to advective flow in the tidal areas, which is of special importance in permeable sandy sediments, pore waters enriched in re-mineralized nutrients and methane are actively released from sediments into the overlying water column (Beck and Brumsack, 2012;Segarra et al, 2013). As Cuxhaven is surrounded by tidal flats, we assume a strong lateral input of methane from these tidal flats.…”

Section: Discussionmentioning

confidence: 99%

Environmental factors affecting methane distribution and bacterial methane oxidation in the German Bight (North Sea)

Osudar

Matoušů

Alawi

et al. 2015

Estuarine, Coastal and Shelf Science

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a b s t r a c tRiver estuaries are responsible for high rates of methane emissions to the atmosphere. The complexity and diversity of estuaries require detailed investigation of methane sources and sinks, as well as of their spatial and seasonal variations. The Elbe river estuary and the adjacent North Sea were chosen as the study site for this survey, which was conducted from October 2010 to June 2012. Using gas chromatography and radiotracer techniques, we measured methane concentrations and methane oxidation (MOX) rates along a 60 km long transect from Cuxhaven to Helgoland. Methane distribution was influenced by input from the methane-rich mouth of the Elbe and gradual dilution by methane-depleted sea water. Methane concentrations near the coast were on average 30 ± 13 nmol L À1 , while in the open sea, they were 14 ± 6 nmol L À1 . Interestingly, the highest methane concentrations were repeatedly detected near Cuxhaven, not in the Elbe River freshwater end-member as previously reported. Though, we did not find clear seasonality we observed temporal methane variations, which depended on temperature and presumably on water discharge from the Elbe River. The highest MOX rates generally coincided with the highest methane concentrations, and varied from 2.6 ± 2.7 near the coast to 0.417 ± 0.529 nmol L À1 d À1 in the open sea. Turnover times varied from 3 to >1000 days. MOX rates were strongly affected by methane concentration, temperature and salinity. We ruled out the supposition that MOX is not an important methane sink in most of the Elbe estuary and adjacent German Bight.

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“…It was shown that both changes in soil moisture content induced by precipitation events and variations in soil temperature can substantially affect the rate and progress of microbially mediated processes in soils and sediments, as well as gas exchange with the atmosphere. In illustration of this point, Suseela et al (2012) demonstrated that seasonally dynamic temperature sensitivity of deep soil heterotrophic respiration in a mesic ecosystem was coupled to changes in soil moisture availability, and Segarra et al (2013) found that CH 4 generation and emission rates in a tidal mudflat were controlled by seasonal changes in sediment saturation. On longer time scales, recharge from precipitation can stimulate microbial respiration, leading to changing patterns in gas generation and consumption (Bekins et al, 2005; Hawley and Altizer, 2011; Conant et al, 2011).…”

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confidence: 99%

Seasonal Variability in Vadose Zone Biodegradation at a Crude Oil Pipeline Rupture Site

Sihota

Trost

Bekins

et al. 2016

Vadose Zone Journal

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Core Ideas Contaminant mass loss rates vary seasonally. Vadose zone temperatures in the source zone correlate with rates of contaminant respiration. Natural soil respiration and gas transport seasonality affect mass loss estimates. Understanding seasonal changes in natural attenuation processes is critical for evaluating source‐zone longevity and informing management decisions. The seasonal variations of natural attenuation were investigated through measurements of surficial CO2 effluxes, shallow soil CO2 radiocarbon contents, subsurface gas concentrations, soil temperature, and volumetric water contents during a 2‐yr period. Surficial CO2 effluxes varied seasonally, with peak values of total soil respiration (TSR) occurring in the late spring and summer. Efflux and radiocarbon data indicated that the fractional contributions of natural soil respiration (NSR) and contaminant soil respiration (CSR) to TSR varied seasonally. The NSR dominated in the spring and summer, and CSR dominated in the fall and winter. Subsurface gas concentrations also varied seasonally, with peak values of CO2 and CH4 occurring in the fall and winter. Vadose zone temperatures and subsurface CO2 concentrations revealed a correlation between contaminant respiration and temperature. A time lag of 5 to 7 mo between peak subsurface CO2 concentrations and peak surface efflux is consistent with travel‐time estimates for subsurface gas migration. Periods of frozen soils coincided with depressed surface CO2 effluxes and elevated CO2 concentrations, pointing to the temporary presence of an ice layer that inhibited gas transport. Quantitative reactive transport simulations demonstrated aspects of the conceptual model developed from field measurements. Overall, results indicated that source‐zone natural attenuation (SZNA) rates and gas transport processes varied seasonally and that the average annual SZNA rate estimated from periodic surface efflux measurements is 60% lower than rates determined from measurements during the summer.

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Seasonal variations of methane fluxes from an unvegetated tidal freshwater mudflat (Hammersmith Creek, GA)

Cited by 18 publications

References 58 publications

High rates of anaerobic methane oxidation in freshwater wetlands reduce potential atmospheric methane emissions

High rates of anaerobic methane oxidation in freshwater wetlands reduce potential atmospheric methane emissions

Environmental factors affecting methane distribution and bacterial methane oxidation in the German Bight (North Sea)

Seasonal Variability in Vadose Zone Biodegradation at a Crude Oil Pipeline Rupture Site

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