Methane Emissions during the Tide Cycle of a Yangtze Estuary Salt Marsh

Abstract

: Methane (CH4) emissions from estuarine wetlands were proved to be influenced by tide movement and inundation conditions notably in many previous studies. Although there have been several researches focusing on the seasonal or annual CH4 emissions, the short-term CH4 emissions during the tide cycles were rarely studied up to now in this area. In order to investigate the CH4 emission pattern during a tide cycle in Yangtze Estuary salt marshes, frequent fixed-point observations of methane flux were carried out using the in-situ static closed chamber technique. The results indicated that the daily average CH4 fluxes varied from 0.68 mgCH4·m−2·h−1 to 4.22 mgCH4·m−2·h−1 with the average flux reaching 1.78 mgCH4·m−2·h−1 from small tide to spring tide in summer. CH4 fluxes did not show consistent variation with both tide levels and inundation time but increased steadily during almost the whole research period. By Pearson correlation analysis, CH4 fluxes were not correlated with both tide levels (R = −0.014, p = 0.979) and solar radiation (R = 0.024, p = 0.865), but significantly correlated with ambient temperature. It is temperature rather than the tide level mainly controlling CH4 emissions during the tide cycles. Besides, CH4 fluxes also showed no significant correlation with the underground pore-water CH4 concentrations, indicating that plant-mediated transport played a more important role in CH4 fluxes compared with its production and consumption.

Subsurface Redox Interactions Regulate Ebullitive Methane Flux in Heterogeneous Mississippi River Deltaic Wetland

“…Vegetation plant functions are beyond the investigation scope, so plant‐mediated gas transport, which varies among plant species and requires detailed information on plant functional types, root density and leaf area, etc., is not included in this model study. Since plant‐mediated transport can be a critical pathway for O 2 , CH 4 , and other gas species to exchange between sediment and atmosphere (Harden & Chaton, 1994; Y. Li et al., 2021; Murray et al., 2019; Villa et al., 2020), the omission of this pathway means that the simulations likely underestimate the surface CH 4 gas flux but may also underestimate CH 4 consumption driven by transport of oxygen into the subsurface.…”

“…Wetlands are estimated to be the largest natural source in the global methane budget (Bhullar et al., 2014; L. Zhang et al., 2010; Z. Zhang et al., 2017), among which freshwater wetlands are considered as the major source; wetlands exposed to high concentrations of sulfate are thought to have low CH 4 emissions due to the inhibition of methane production by sulfate‐reducing bacteria (Davidson et al., 2021; King & Wiebe, 1980; Poffenbarger et al., 2011). Even within the same type of wetland (e.g., salt marsh, brackish marsh, or freshwater marsh), large variability has been observed in surface methane flux on different temporal scales from hourly to seasonal (Capooci & Vargas, 2022; Delwiche et al., 2021; Goodrich et al., 2011; Y. Li et al., 2021).…”

Empirical Dynamic Modeling Reveals Complexity of Methane Fluxes in a Temperate Salt Marsh

“…Two steps are applied before CCM, which provide information about the time series of interest (CH 4 ) (Li et al., 2021). The initial step is determining the embedding dimension ( e ) via the function EmbedDimension , which iteratively takes successively longer lags of a set time period defined by the parameter Tau (Ƭ).…”

Empirical Dynamic Modeling Reveals Complexity of Methane Fluxes in a Temperate Salt Marsh

“…12 Two steps are applied before CCM, which provide information about the time series of interest (CH 4 ) (Li et al 2021). The initial step is determining the embedding dimension (e) via the function EmbedDimension, which iteratively takes successively longer lags of a set time period defined by the parameter Tau (Ƭ).…”