Carbon fluxes in estuarine wetlands based on a material flow perspective

Estuarine wetland is important component of continental shelf and blue carbon system. The regulation and enhancement of the carbon pool in estuarine wetlands are contingent upon a clear understanding of the carbon cycle. Given that dynamic material flow is a landmark feature of estuarine wetlands, interpreting this process from a vertical and horizontal material flow perspective may offer a potential breakthrough. However, the impacts of the material exchange in estuaries on the key processes of carbon exchange in estuarine wetlands and the mechanism of carbon sink formation are not well understood. To accurately assess and predict the dynamic capacity of carbon pools in estuarine wetlands, this review summarizes the vertical carbon flux processes in estuarine wetlands, which are believed to be dominated by plant and soil material transport, as well as the horizontal carbon flux processes influenced by hydrological conditions. In addition, we discuss the impacts of carbon and nutrient fluxes from submarine groundwater discharge (SGD), which accompany estuarine wetlands, on the systematic carbon cycling. Finally, we offer a series of recommendations to bridge existing knowledge gaps and contribute to the broader scientific discourse on the carbon cycle in estuarine wetlands.