## 1 Introduction  
Mangrove wetlands exhibit significant carbon storage potential, in spite of their restricted area [1]. The annual CO\({}_{2}\) absorption rate of mangroves is about eight times that of inland wetlands [2]. However, their role in the global carbon cycle is complex, as mangroves also emit methane (CH\({}_{4}\)), a potent greenhouse gas with a warming potential 27-29.8 times higher than CO\({}_{2}\) over a 100-year timescale [3]. The net ecosystem exchange (NEE) of CO\({}_{2}\) and CH\({}_{4}\) fluxes in mangroves thus represents a delicate balance between carbon absorption and greenhouse gas emissions, which can be upset by extreme climatic events such as storm surges. With climate change amplifying the frequency and intensity of storm surges [4],particularly in vulnerable coastal regions, it is increasingly vital to understand how different types of mangrove ecosystems--both restored and natural--respond to such extreme events. This study provides novel insights into the distinct response mechanisms of NEE and CH4 fluxes under storm surge stress, highlighting the contrasting carbon dynamics between restored and natural mangroves. These findings are critical for refining blue carbon budgets and offer a scientific foundation for evidence-based coastal management, restoration strategies, and long-term climate mitigation planning. NEE serves as a key indicator of mangrove carbon sink strength. Methane emissions, though comparatively smaller in magnitude, are a critical component of mangrove greenhouse gas budgets due to CH4's high global warming potential [3]. Natural mangrove forests, with their complex root systems and anoxic soils, have evolved mechanisms to balance carbon sequestration and methane production. In contrast, restored mangroves--typically established in degraded or anthropogenically altered habitats--may exhibit divergent carbon cycling behaviors due to differences in community structure, microbial community composition, and soil nutrient cycling [5]. Ecosystem and atmospheric CO2 exchange is commonly measured using the eddy covariance technique (EC), which allows long-term, continuous, large-scale monitoring of carbon flux data to quantify the carbon source-sink function of ecosystems [6; 7]. Mangrove ecosystems are particularly susceptible to storm surges given their coastal position. Despite mangroves being regarded as disturbance-adapted ecosystems, the increasing intensity and numbers of storm surges will exacerbate threats to mangrove ecosystems [8]. Storm surges, characterized by rapid seawater inundation and sediment deposition, can transiently or permanently alter these processes by modulating oxygen availability, salinity stress, and organic matter decomposition rates. Such disturbances may shift mangrove ecosystems from net carbon sinks to temporary sources, with implications for their role in climate mitigation [9]. Storm surges introduce abrupt salinity changes, which suppress sulfate-reducing bacteria while favoring methanogens. For instance, [PERSON] et al. [10] found that drought-induced salinity spikes reduced both CO2 sequestration and CH4 emissions in mangroves, but storm surges may reverse this trend by diluting soil salinity temporarily. Storm surges inundate mangroves with saline water, prolonging anaerobic conditions in soils. This suppresses aerobic respiration but promotes CH4 production. In the Pearl River Delta, restored mangroves with low salinity exhibited elevated CH4 emissions (24.7-26.3 g C m\({}^{-2}\) yr\({}^{-1}\)) due to prolonged flooding, contrasting with natural mangroves that act as stronger carbon sinks [11]. However, existing studies on mangrove carbon fluxes often focus on baseline conditions, neglecting episodic disturbances such as storm surges, especially for the natural and restored mangroves. [PERSON] et al. (2000) [12] demonstrated that typhoon-induced damage to mangrove forests is influenced by stand origin, stand density, and stand age.