Seasonal Variation of Methane Fluxes in a Mangrove Ecosystem in South India: An Eddy Covariance-Based Approach

Gnanamoorthy, Palingamoorthy; Chakraborty, Supriyo; Nagarajan, R.; Ramasubramanian, R.; Selvam, V.; Burman, Pramit Kumar Deb; Sarathy, Palanivel Partha; Zeeshan, Mohd; Song, Qinghai; Zhang, Yiping

doi:10.1007/s12237-021-00988-1

Cited by 10 publications

(9 citation statements)

References 97 publications

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“…To our knowledge, the highest fluxes from these systems showed F CH4 rates of 54.8 g C m −2 y −1 (Jha et al., 2014). Most mangrove forests, however, had lower emissions of CH 4 , ranging from 6–15.6 g C m −2 y −1 (Gnanamoorthy et al., 2022; Liu et al., 2020). Additionally, this is accompanied by a much higher annual uptake of CO 2 (Table 4, Barr et al., 2012; Liu et al., 2020; Troxler et al., 2015).…”

Section: Discussionmentioning

confidence: 99%

Carbon Dynamics of a Coastal Wetland Transitioning to Mangrove Forest

Yannick,

Oberbauer,

Staudhammer

et al. 2024

JGR Biogeosciences

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Coastal wetlands play a vital role in the global carbon cycle and are under pressure from multiple anthropogenic influences. Altered hydrology and land use change increase susceptibility of wetlands to sea‐level rise, saltwater intrusion, tidal flood events, and storm surges. Flooding from perigean spring tides and storm surges rapidly inundates coastal wetlands with saline waters, quickly surpassing vegetation tolerances, leading to shifts in soil microbial respiration, peat collapse, and plant mortality, followed by establishment of salt‐tolerant vegetation. The Southeast Saline Everglades (SESE) is facing many of these pressures, making it a model system to examine the impacts of ecosystem state transitions and their carbon dynamics. Saltwater flooding from Hurricane Irma (2017) initiated a transitional state, where less salt‐tolerant vegetation (e.g., Cladium jamaicense) is declining, allowing halophytic species such as Rhizophora mangle to colonize, altering the ecosystem's biogeochemistry. We utilized eddy covariance techniques in the SESE to measure ecosystem fluxes of CO2 and CH4 in an area that is transitioning to an alternative state. The landward expansion of mangroves is increasing leaf area, leading to greater physiological activity and higher biomass. Our site was presented initially as a small C source (47.0 g C m−2) in 2020, and by 2022 was a sink (−84.24 g C m−2), with annual greenhouse carbon balance ranging from −0.04 to 0.18. Net radiative forcing ranged from 2.04 to 2.27 W m−2 d−1. As the mangrove landward margin expands, this may lead the area to become a greater carbon sink and a potential offset to increasing atmospheric CO2 concentrations.

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Section: Discussionmentioning

confidence: 99%

Carbon Dynamics of a Coastal Wetland Transitioning to Mangrove Forest

Yannick,

Oberbauer,

Staudhammer

et al. 2024

JGR Biogeosciences

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“…Diel tidal activities have also been found to promote CH 4 emission via tidal pumping of CH 4 -rich porewater and groundwater (Santos et al, 2019). These complexities justify the inconsistent findings in previous studies showing larger CH 4 emission in the daytime (Gnanamoorthy et al, 2022;Liu et al, 2020), nighttime (Zhu, Sun, & Qin, 2021), or no clear diel pattern (Jha et al, 2014).…”

Section: Introductionmentioning

confidence: 97%

“…Due to technical, logistical, and financial constraints, the acquisition of multi-year high-frequency CH 4 flux time series in mangroves is almost impossible until recent years with the application of robust eddy covariance (EC) method (Knox et al, 2019). Although there are over 200 EC sites worldwide for CH 4 flux measurements most established in the past decade (Knox et al, 2019), we're aware of only five sites reporting mangrove CH 4 flux so far with relatively short records from several months (Gnanamoorthy et al, 2022;Jha et al, 2014) to two/three years (Liu et al, 2020;Zhao et al, 2022;Zhu, Sun, & Qin, 2021). These EC studies provided a high-frequency CH 4 flux time series commonly at a 30-min resolution, serving as an important complement to previous chamber-based flux measurements that were usually low-frequency and thus unable to accurately interpret temporal variability of CH 4 flux, especially at short time scale (e.g., diel).…”

Section: Introductionmentioning

confidence: 99%

Asynchronous Methane and Carbon Dioxide Fluxes Drive Temporal Variability of Mangrove Blue Carbon Sequestration

Zhu,

Chen,

et al. 2024

Geophysical Research Letters

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The climate benefit of blue carbon sequestered by mangrove forests can be partially offset by CH4 emission, but this offset is rarely assessed using multi‐year high‐frequency measurements. Here, four‐year eddy covariance measurements were used to examine temporal patterns of CH4 flux and its blue carbon offset (i.e., reduced climate benefit) in a subtropical estuarine mangrove in China. We found both diel and seasonal CH4 fluxes were mainly driven by soil temperature and tidal activities, showing greater nighttime emission. On average, one‐tenth of CO2 uptake was offset by CH4 emission using the sustained‐flux global warming potential metric at a 20‐year time horizon, while this offset could vary over an order of magnitude due to asynchronous fluxes of CH4 and CO2 across diel and seasonal cycles. These results highlight the significant contribution of nighttime emission to mangrove CH4 budget and the importance of asynchronous flux variations in assessing mangrove's climate benefit.

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“…Particularly in mangroves, tides may have a profound influence on F CH4 by regulating water table depth, sulfate concentrations, oxygen availability, soil temperature, and the transport of vertical gases and aqueous carbon (Li et al., 2018). For example, high concentrations of sulfate in mangroves can inhibit F CH4 because sulfate‐reducing bacteria can outcompete methanogens for their common substrates (Gnanamoorthy et al., 2021; Purvaja et al., 2004).…”

Section: Introductionmentioning

confidence: 99%

“…The eddy covariance technique has emerged as a widespread means of quantifying real-time exchange of carbon, water, and energy fluxes between the biosphere and the atmosphere because it can provide high-frequency and near-continuous flux data at the ecosystem scale (Baldocchi, 2003(Baldocchi, , 2014. Eddy covariance measurements of CH 4 fluxes (F CH4 ) have been implemented in more than 200 sites across different landscapes (e.g., wetlands, croplands, forests and grasslands) (Delwiche et al, 2021;Knox et al, 2019), including mangrove sites in China (Liu et al, 2020;Zhao et al, 2021) and India (Gnanamoorthy et al, 2021;Jha et al, 2014). However, the high complexity of internal processes that dominates the production and transport of wetland F CH4 poses various challenges when investigating and interpreting these data using traditional analysis methods (Knox et al, 2021;Sturtevant et al, 2016):…”

mentioning

confidence: 99%

Biophysical Controls of Ecosystem‐Scale Methane Fluxes From a Subtropical Estuarine Mangrove: Multiscale, Nonlinearity, Asynchrony and Causality

Liu

Valach

Baldocchi

et al. 2022

Global Biogeochemical Cycles

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Mangroves are complex ecosystems subject to periodic and irregular changes in meteorology, tides, water quality and biological factors. Methane dynamics in mangroves and their dependence on biogeochemical controls across scales are poorly characterized using traditional parametric statistics. We measured the ecosystem‐scale methane flux (FCH4) using an eddy covariance system in a subtropical estuarine mangrove for two years. A combination of nonparametric statistical approaches, including singular spectrum analysis and information theory, was used to isolate multiscale FCH4 variations and explore their variability and dominant controls at different time scales. FCH4 exhibited the largest variability at the diel scale (57%), followed by seasonal (25%) and multiday (18%) scales. Mutual information metrics suggested that variation in FCH4 was dominantly coupled to plant activities through synchronous processes at the diel scale. Moreover, fluctuations in atmospheric turbulence and soil temperature dominated multiday variation in FCH4 through asynchronous processes. Seasonally, soil temperature and water salinity were dominant variables leading to changes in FCH4 with a time lag of 12 and 17 days, respectively. Weak links between FCH4 and tidal heights were found across all the studied time scales. Transfer entropy metrics indicated that a super typhoon event substantially weakened causal links between biophysical variables and FCH4 by causing severe defoliation and disturbing the soil microbial community. The typhoon also temporarily decoupled the causal link between FCH4 and temperature. These findings call for the inclusion of the properties of scale emergence, nonlinearity, asynchrony and causality for comprehensively understanding and accurately predicting the interactions between mangrove FCH4 and its biophysical controls.

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Seasonal Variation of Methane Fluxes in a Mangrove Ecosystem in South India: An Eddy Covariance-Based Approach

Cited by 10 publications

References 97 publications

Carbon Dynamics of a Coastal Wetland Transitioning to Mangrove Forest

Carbon Dynamics of a Coastal Wetland Transitioning to Mangrove Forest

Asynchronous Methane and Carbon Dioxide Fluxes Drive Temporal Variability of Mangrove Blue Carbon Sequestration

Biophysical Controls of Ecosystem‐Scale Methane Fluxes From a Subtropical Estuarine Mangrove: Multiscale, Nonlinearity, Asynchrony and Causality

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