Bay morphology and soil chemistry govern spatiotemporal variability in porewater carbon exchange in coastal mangroves

Authors: LI, X - Beijing Normal University; SHI, K - Beijing Normal University; FANG, L - Beijing Normal University; PENG, Y - Beijing Normal University; YANG, Q - Hong Kong University Of Science; SU, G - Beijing Normal University; ZHANG, C - Beijing Normal University; WANG, J - Jinan University; DU, L - University Of Maryland; McCarty, Gregory

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2025
Publication Date: 3/24/2025
Citation: Li, X., Shi, K., Fang, L., Peng, Y., Yang, Q., Su, G., Zhang, C., Wang, J., Du, L., Mccarty, G.W. 2025. Bay morphology and soil chemistry govern spatiotemporal variability in porewater carbon exchange in coastal mangroves. Journal of Hydrology. 657. https://doi.org/10.1016/j.jhydrol.2025.133159.
DOI: https://doi.org/10.1016/j.jhydrol.2025.133159

Interpretive Summary: Understanding the spatiotemporal variability of lateral carbon exchanges in mangroves is essential for assessing their role in global carbon sequestration and potential impacts on climate change. To assess these carbon exchange dynamics, a study was conducted using mangrove ecosystems in coastal regions of the Pearl River Delta in China. The study resulted in development of a predictive causal model quantifying the important lateral carbon exchange pathways. This study demonstrated the feasibility of utilizing these key metrics, especially easily accessible ones like bay morphology indices and tidal flow hours, to quantify dissolved inorganic and organic carbon exchanges in mangroves. It offers a straightforward approach for evaluating carbon lateral exchanges in coastal mangroves and has significant implications for large-scale carbon flux estimation.

Technical Abstract: Understanding the spatiotemporal variability of lateral carbon exchanges in mangroves is essential for assessing their role in global carbon sequestration and potential impacts on climate change. This is particularly important in coastal regions like the Pearl River Delta, where highly diverse mangroves are present but are subjected to anthropogenic disturbances. This study examines the variability of porewater dissolved inorganic carbon (pDIC) and dissolved organic carbon (pDOC) interplay in mangroves in the Pearl River Delta, emphasizing the role of tidal hydrology, water chemistry, soil chemistry, and bay morphology in these carbon exchanges. Across five mangrove sites, we detected a strong correlation (r= 0.870) between the spatiotemporal variability of pDIC and pDOC, exhibiting significant negative trends related to tidal flow hours. Soil chemistry had the most substantial impact on pDOC concentrations, accounting for 51% of its variance, while bay morphology, soil chemistry, and pDOC concentrations similarly impacted pDIC, each accounting for about 25% of the pDIC variance. Specifically, indices such as roundness, area, and perimeter in bay morphology, along with soil DOC, soil organic carbon (SOC), and soil total nitrogen, pH, oxidation-reduction potential (ORP) and water nitrogen in water chemistry, as well as tidal flow hours, water temperature, and water depth in tidal hydrology, were all found to significantly influence dyanamics of pDIC and pDOC. This study demonstrated the feasibility of utilizing these key metrics—especially easily accessible ones like bay morphology indices and tidal flow hours—to quantify pDIC and pDOC exchanges in mangroves. It offers a straightforward approach for evaluating carbon lateral exchanges in coastal mangroves and has significant implications for large-scale carbon flux estimation.