CH4 emissions partially offset net ecosystem CO2 uptake in the Cyperus malaccensis salt marsh in Min River estuary

Jiang Shaofeng; Tong Chuan; Fang Shuyuan; Huang Jiafang; Yu Yixuan; Gao Jujuan; Li Lin

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Jiang Shaofeng，Tong Chuan，Fang Shuyuan, et al. CH4 emissions partially offset net ecosystem CO2 uptake in the Cyperus malaccensis salt marsh in Min River estuary[J]. Haiyang Xuebao，2026, 48(x)：1–12

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Jiang Shaofeng，Tong Chuan，Fang Shuyuan, et al. CH₄ emissions partially offset net ecosystem CO₂ uptake in the Cyperus malaccensis salt marsh in Min River estuary[J]. Haiyang Xuebao，2026, 48(x)：1–12

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CH₄ emissions partially offset net ecosystem CO₂ uptake in the Cyperus malaccensis salt marsh in Min River estuary

Jiang Shaofeng^1
,,
Tong Chuan^{1, 2, 3, 4
,
,},
Fang Shuyuan¹,
Huang Jiafang^{1, 2, 3, 4},
Yu Yixuan¹,
Gao Jujuan^{3, 4},
Li Lin¹

1.
School of Geographical Sciences, Fujian Normal University, Fuzhou 350007, China
2.
Key Laboratory of Humid Subtropical Eco-geographical Process, Ministry of Education, Fujian Normal University, Fuzhou 350007, China
3.
Wetland Ecosystem Research Station of Minjiang Estuary, National Forestry and Grassland Administration, Fuzhou 350215, China
4.
Fuzhou Coastal Wetland Ecology Research Center, Fuzhou 350215, China

Received Date: 2026-03-08
Rev Recd Date: 2026-04-23

Available Online: 2026-05-27

Abstract

Abstract

Coastal salt marsh ecosystems exhibit high efficiency in carbon fixation and storage, but they are also non-negligible sources of methane (CH₄) emissions. Global Warming Potential (GWP) is an indicator that measures the warming effect of a unit mass of greenhouse gas relative to CO₂ over a specific time horizon. The GWP of CH₄ over long timescales is significantly higher than that of carbon dioxide (CO₂). Therefore, scientific quantification of offset intensity of net ecosystem CO₂ uptake by CH₄ emissions in coastal salt marshes and accurate determination of ecosystem carbon sink rates are crucial to assess the carbon sink magnitude of blue carbon ecosystems at regional scales. This study employed a combination of techniques, including a “transparent chamber combined with shades of varying light transmittance, trace gas infrared analyzers, and modeling” to conduct high-frequency observations and assessment of the net ecosystem exchange of CO₂ (NEE) and ecosystem respiration (ER) in the Cyperus malaccensis salt marsh of the Minjiang River Estuary, simultaneously, also measured the CH₄ fluxes , and finally quantified the annual carbon sink rate of the C. malaccensis salt marsh and the offset of net ecosystem CO₂ uptake by CH₄ emissions. NEE of the C. malaccensis salt marsh exhibited significant seasonal variation, with net atmospheric CO₂ uptake occurring in all months. The annual NEE was −5970.2 ± 895.9 g CO₂/(m²·a). and the annual CH₄ flux was 18.5 ± 0.2 g CH₄/(m²·a). Considering theGWP₂₀ and GWP₁₀₀, the ecosystem carbon sink rates of the C. malaccensis salt marsh were 4543.47 and 5486.8 g CO₂-eq/(m²·a), respectively. The offset ratios of net ecosystem CO₂ uptake by CH₄ emissions were 25.7% and 8.7%, respectively. Although CH₄ emissions partially offset the net ecosystem CO₂ uptake in the C. malaccensis salt marsh of the Minjiang River Estuary, the C. malaccensis salt marsh ecosystem still exhibits a strong carbon sink function, and plays a significant role in mitigating global climate warming.
- net ecosystem exchange of CO₂,
- CH₄ emission,
- carbon sink rate,
- offset,
- Cyperus malaccensis salt marsh,
- coastal blue carbon ecosystem

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References(29)

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