[Spatial variations of carbon stock in tidal flat sediments of Zhoushan Archipelago]

Tidal flats, a type of blue carbon ecosystems, play a crucial role in enhancing carbon storage capacity of natural ecosystems and addressing climate change. The organic carbon stored in tidal flat sediments is a key component of their carbon sequestration function but is dependent on habitat factors such as topographic features and depositional environments. To investigate the spatial variations of carbon storage in tidal flat sediments and their primary regulating factors at the regional scale, we selected six typical islands in the Zhoushan Archipelago as research areas, systematically analyzed the spatial distribution characteristics of sedimentary organic carbon storage and quantified the impact of sediment physicochemical factors on carbon storage capacity using the Absolute Principal Component Score-Multiple Linear Regression (APCS-MLR) model. The results showed that there was significant spatial heterogeneity in sedimentary carbon storage among sampling sites, with the highest carbon storage value being recorded on Daishan Island (68.96 Mg C·hm^-2) and the lowest on Liuheng Island (50.96 Mg C·hm^-2). Most sampling sites showed no significant differences in organic carbon storage between the surface layer (0-30 cm), intermediate layer (30-60 cm), and bottom layer (>60 cm). The APCS-MLR model identified three principal components, with particle size structure, sedimentary state, and salinity-alkalinity characteristics contributing 37.0%, 29.0%, and 20.0% to the carbon storage capacity of tidal flat sediments in the Zhoushan Archipelago, respectively. Particle size structure and sedimentary depth exhibited significant correlations with carbon storage, while there was no relationship between sedimentary state and salinity-alkalinity characteristics and carbon storage. This study would enhance understanding of carbon storage mechanisms in tidal flat sediments and provide scientific support and decision-making for regional blue carbon estimation and coastal carbon sink management.