Fate of terrigenous organic carbon within shelf sediments from the East China Sea controlled by sea-level and climatic changes since the last deglaciation

The deposition of organic carbon in marine sediments plays a critical role in global carbon sequestration. The East China Sea (ECS) inner shelf, dominated by large river systems, receives significant inputs of terrestrial organic carbon transported by rivers, offering valuable insights into the fate of terrigenous organic carbon in response to sea-level and climatic changes. Based on the total organic carbon (TOC) contents, δ13C values of the TOC, and dry bulk density of core ECMZ, as well as comprehensive analysis of core EC2005 data, our results indicate that sedimentary organic carbon in core ECMZ exhibits mixed sources, with terrigenous organic carbon contributing up to 80%. On a long timescale, the burial of terrigenous organic carbon is primarily controlled by the evolution of the depositional environment and the East Asian summer monsoon, with stronger monsoons leading to increased terrigenous organic matter transport from the Changjiang River into the ECS inner shelf. During the deglacial and Holocene cold periods, the proportion of terrigenous organic carbon peaks due to the influence of the East Asian winter monsoon. Spatially, the proportion of terrigenous components decreases with distance from the estuary, while sedimentation rate emerges as a key controlling factor for terrigenous organic carbon deposition flux. Estimations suggest that since 17.5 ka, the flux of terrigenous organic carbon on the ECS inner shelf has averaged 3 × 103 t C km−2 a−1, with a TOC flux ranging from 4 to 5 × 103 t C km−2 a−1. These findings deepen our understanding of the dynamics of terrigenous organic carbon deposition in the ECS inner shelf and underscore the importance of climatic variability in shaping carbon burial processes in marginal seas.