Closing the Coastal Wetlands Carbon Budget using tower-based measurements, soil carbon accumulation rates and high resolution lateral carbon flux observations

Coastal wetlands - an important blue carbon ecosystems - are an exceptionally efficient carbon storage sinks on Earth with high carbon sequestration capacity, contributing significantly to combating climate change. Accurate carbon budgeting of coastal marshes requires a complete understanding of different processes/components including the net ecosystem exchange of CO2 with atmosphere, the lateral carbon export lost with tidal draining, and the soil carbon accumulation rate. Yet, most, if not all, current studies present these three components separately, largely due to the knowledge gaps among the diffferent disciplines. Here, for the first time, we bring together measurements of eddy-covaiance flux tower, soil carbon burial data, and lateral carbon export measurements collected in the Xisha marsh - a tidal freshwater wetlands near the first order of Yangtze bifurcation in the Yangtze river delta. Each data set is collected, processed and analyzed in part with disciplinary methodologies. High resolution measurements of time series lateral carbon continuted for one complete hydrological cycle in the system and results show that teh lateral carbon loss with tides contribute up to 20% in this dynamic estuarine blue carbon system. This study highlights the importance of taking the lateral carbon loss into consideration for better closing up the estuarine blue carbon budget.