Source-sink dynamics of coastal blue carbon: a review of mechanisms and drivers

Within the context of global climate change, coastal blue carbon ecosystems (e.g., mangroves, salt marshes, seagrass meadows, and macroalgae) have emerged as critical natural carbon sinks. Yet, persistent methodological inconsistencies and geographic biases hinder their reliable incorporation into blue carbon management and climate prediction. Here, we synthesize current understanding of source-sink characteristics, drivers, and formation mechanisms of coastal blue carbon ecosystems, focusing on carbon storage capacity, sequestration pathways, and spatial heterogeneity across ecosystem types. We emphasize biogeochemical processes, including sedimentation, tidal dynamics, and microbial mediation, and critically examine anthropogenic disturbances—coastal development, land-use change, pollution, and ecosystem degradation—on blue carbon dynamics. Finally, we identify critical knowledge gaps, particularly the quantification of lateral carbon fluxes and microbial carbon stabilization mechanisms, highlighting the need for integrated, multi-scale monitoring to better assess the climate mitigation potential of coastal blue carbon ecosystems.