## 1 Introduction  
Gross primary productivity (GPP), the total amount of carbon absorbed by green plants through photosynthesis, reflects the productivity level of ecosystems in natural environments and is a fundamental component of the carbon cycle [1]. Evapotranspiration(ET) encompasses both water evaporation (the movement of water to the air directly from the Earth's surface) and transpiration (evaporation that occurs mainly through the stomata of plant leaves). It connects the processes of stomatal function, water consumption, and photosynthetic carbon sequestration of plant leaves, thus playing a critical role in carbon and water cycling and energy balance in terrestrial ecosystems. As two fundamental processes, GPP and ET are indispensable to carbon and water cycles across multiple spatial scales [2; 3; 4]. They are interconnected through biochemical processes in plants [5] and are coupled at different spatial and temporal scales. Existing research indicates that variations in temperature, precipitation, and light intensity affect photosynthesis, respiration, transpiration, and soil properties in ecosystems [6; 7; 8], thereby influencing carbon and water cycling processes. In low-latitude regions, changes in GPP are primarily influenced by precipitation, while in mid- to high-latitude regions, they are mainly influenced by temperature [9]. Additionally, compared to other ecosystems, wetland ecosystems are less affected by water availability and more influenced by temperature [10]. Temperature also affects stomatal conductance in vegetation, thereby influencing photosynthetic and respiration rates. Simultaneously, light intensity impacts photosynthetically active radiation, thereby impacting photosynthetic rates and influencing carbon and water cycling processes [11]. Solar-induced chlorophyll fluorescence (SIF), an important optical signal emitted in the spectral range of 650-800 nm, is produced by plants during photosynthesis, in addition to the energy used for heat dissipation and light reactions. Incorporating remotely sensed SIF signals into carbon and water cycle modeling can not only help track how ecosystem functioning responds to environmental change across large spatial domains [12; 13; 14] but also reduce the uncertainty in ecosystem carbon and water cycle modeling [15; 16; 17]. Previous research [18; 19; 20] has shown a strong correlation between SIF and GPP across various vegetation types at various spatial and temporal scales. Additionally, a significant non-linear correlation between ET and SIF has also been found [21]. Therefore, SIF demonstrates significant potential as an effective indicator for GPP and ET in ecosystems with high spatiotemporal resolution. As an interface connecting terrestrial and marine ecosystems, coastal wetlands are among the most productive ecosystems on Earth [22]. However, coastal wetland ecosystems are particularly vulnerable due to river-tide interactions [23]. Periodic tidal fluctuations constitute a unique hydrological feature of coastal wetlands, inducing variations in inundation levels and salinity that impact carbon and water cycling processes. More specifically, tides may influence ecosystem photosynthesis, transpiration, and the emission of chlorophyll fluorescence, as tidal flooding tends to induce hypoxia and salt stress, leading to physiological and biochemical changes in plants, such as reductions in enzyme activity and stomatal conductance [24]. Simultaneously, tidal flooding also affects the radiative transfer process and the detection of SIF [25]. Therefore, in addition to meteorological factors, the GPP, SIF, and ET of coastal wetland ecosystems are also influenced by tidal inundation and associated salinity changes. Furthermore, given the limited area and high heterogeneity of coastal wetlands, coupled with tidal-induced short-term vegetation changes, high-resolution remote sensing is crucial for large-scale GPP and ET estimation.