Carbon Flux Trajectories and Site Conditions from Restored Impounded Marshes in the Sacramento‐San Joaquin Delta

Valach, Alex; Kasak, Kuno; Hemes, Kyle S.; Szutu, Daphne; Verfaillie, Joe; Baldocchi, Dennis

doi:10.1002/9781119639305.ch13

Cited by 7 publications

(8 citation statements)

References 151 publications

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“…S5). High CH 4 emissions at that site during our sampling may also be attributed to its recent conversion to a restored wetland and the subsequent increase in primary productivity and labile carbon inputs; CH 4 emissions have since declined both there and at West Pond over time (2012–2020) ( 47 ). High CH 4 production has also been observed in oligohaline wetlands in the Delaware River estuary where isotopic measurements indicated patterns across the salinity gradient were driven more by a lack of CH 4 consumption than by greater gross CH 4 production ( 42 ).…”

Section: Discussionmentioning

confidence: 97%

Multiple microbial guilds mediate soil methane cycling along a wetland salinity gradient

Hartman,

Bueno de Mesquita,

Theroux

et al. 2024

mSystems

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Estuarine wetlands harbor considerable carbon stocks, but rising sea levels could affect their ability to sequester soil carbon as well as their potential to emit methane (CH 4 ). While sulfate loading from seawater intrusion may reduce CH 4 production due to the higher energy yield of microbial sulfate reduction, existing studies suggest other factors are likely at play. Our study of 11 wetland complexes spanning a natural salinity and productivity gradient across the San Francisco Bay and Delta found that while CH 4 fluxes generally declined with salinity, they were highest in oligohaline wetlands (ca. 3-ppt salinity). Methanogens and methanogenesis genes were weakly correlated with CH 4 fluxes but alone did not explain the highest rates observed. Taxonomic and functional gene data suggested that other microbial guilds that influence carbon and nitrogen cycling need to be accounted for to better predict CH 4 fluxes at landscape scales. Higher methane production occurring near the freshwater boundary with slight salinization (and sulfate incursion) might result from increased sulfate-reducing fermenter and syntrophic populations, which can produce substrates used by methanogens. Moreover, higher salinities can solubilize ionically bound ammonium abundant in the lower salinity wetland soils examined here, which could inhibit methanotrophs and potentially contribute to greater CH 4 fluxes observed in oligohaline sediments. IMPORTANCE Low-level salinity intrusion could increase CH4 flux in tidal freshwater wetlands, while higher levels of salinization might instead decrease CH4 fluxes. High CH4 emissions in oligohaline sites are concerning because seawater intrusion will cause tidal freshwater wetlands to become oligohaline. Methanogenesis genes alone did not account for landscape patterns of CH4 fluxes, suggesting mechanisms altering methanogenesis, methanotrophy, nitrogen cycling, and ammonium release, and increasing decomposition and syntrophic bacterial populations could contribute to increases in net CH4 flux at oligohaline salinities. Improved understanding of these influences on net CH4 emissions could improve restoration efforts and accounting of carbon sequestration in estuarine wetlands. More pristine reference sites may have older and more abundant organic matter with higher carbon:nitrogen compared to wetlands impacted by agricultural activity and may present different interactions between salinity and CH4. This distinction might be critical for modeling efforts to scale up biogeochemical process interactions in estuarine wetlands.

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Section: Discussionmentioning

confidence: 97%

Multiple microbial guilds mediate soil methane cycling along a wetland salinity gradient

Hartman,

Bueno de Mesquita,

Theroux

et al. 2024

mSystems

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“…Methane emissions are inherently linked to plant productivity (Bridgham et al., 2013); thus, reductions in NEE due to disturbance were often accompanied by reductions in FCH 4 (Figure ) (Chamberlain et al., 2020; Sturtevant et al., 2016). Unintended short‐term water drawdowns have become more frequent in recent years, influencing FCH 4 on multiple time scales and seemingly causing an overall decreasing trend at the young and old managed wetlands (Figure ) (Valach et al., 2021). This trend contrasts with those observed at other restored nontidal wetlands in the Delta (Valach et al., 2021), suggesting that ongoing site‐specific factors might be driving FCH 4 variability.…”

Section: Discussionmentioning

confidence: 99%

“…Unintended short‐term water drawdowns have become more frequent in recent years, influencing FCH 4 on multiple time scales and seemingly causing an overall decreasing trend at the young and old managed wetlands (Figure ) (Valach et al., 2021). This trend contrasts with those observed at other restored nontidal wetlands in the Delta (Valach et al., 2021), suggesting that ongoing site‐specific factors might be driving FCH 4 variability. The shorter record of greenhouse gas exchange at the restored tidal wetland complicates assessing interannual variability, however, the 3 years of NEE recorded at this site are similar (average: −386, range of 95 g C−CO 2 m −2 yr −1 ).…”

Section: Discussionmentioning

confidence: 99%

Tidal and Nontidal Marsh Restoration: A Trade‐Off Between Carbon Sequestration, Methane Emissions, and Soil Accretion

et al. 2021

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Coastal wetlands are sites of high carbon (C) sequestration rates through continuous vertical accretion owing to both, their capacity to trap allochthonous sediments and the allocation of a large fraction of their production to roots and rhizomes (Duarte et al., 2013). Their high rates of photosynthetic C fixation and the low rates of organic matter decomposition in their waterlogged and oxygen-poor soils promote the preservation

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“…It is thus important to understand the drivers of wetland CH 4 emissions, especially given that there has been much recent discussion of the potential for coastal and estuarine wetlands to sequester vast quantities of carbon in what has been referred to as “blue carbon” (4–7). However, any increases in carbon (C) storage could potentially be offset by greenhouse gas emissions (8–10), which warrants further study and quantification.…”

Section: Introductionmentioning

confidence: 99%

Microbial ecology and site characteristics underlie differences in salinity-methane relationships in coastal wetlands

Bueno de Mesquita,

Hartman,

Ardón

et al. 2024

Preprint

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Methane (CH4) is a potent greenhouse gas emitted by archaea in anaerobic environments such as wetland soils. Tidal freshwater wetlands are predicted to become increasingly saline as sea levels rise due to climate change. Previous work has shown that increases in salinity generally decrease CH4 emissions, but with considerable variation, including instances where salinization increased CH4 flux. We measured microbial community composition, biogeochemistry, and CH4 flux from field samples and lab experiments from four different sites across a wide geographic range. We sought to assess how site differences and microbial ecology affect how CH4 emissions are influenced by salinization. CH4 flux was generally, but not always, positively correlated with CO2 flux, soil carbon, ammonium, phosphate, and pH. Methanogen guilds were positively correlated with CH4 flux across all sites, while methanotroph guilds were both positively and negatively correlated with CH4 depending on site. There was mixed support for negative relationships between CH4 fluxes and concentrations of alternative electron acceptors and abundances of taxa that reduce them. CH4/salinity relationships ranged from negative, to neutral, to positive and appeared to be influenced by site characteristics such as pH and plant composition, which also likely contributed to site differences in microbial communities. The activity of site-specific microbes that may respond differently to low-level salinity increases is likely an important driver of CH4/salinity relationships. Our results suggest several factors that make it difficult to generalize CH4/salinity relationships and highlight the need for paired microbial and flux measurements across a broader range of sites.

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Carbon Flux Trajectories and Site Conditions from Restored Impounded Marshes in the Sacramento‐San Joaquin Delta

Cited by 7 publications

References 151 publications

Multiple microbial guilds mediate soil methane cycling along a wetland salinity gradient

Multiple microbial guilds mediate soil methane cycling along a wetland salinity gradient

Tidal and Nontidal Marsh Restoration: A Trade‐Off Between Carbon Sequestration, Methane Emissions, and Soil Accretion

Microbial ecology and site characteristics underlie differences in salinity-methane relationships in coastal wetlands

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