Sources, dispersal and preservation of sedimentary organic matter in the Yellow Sea: The importance of depositional hydrodynamic forcing

The sources, distribution and fate of sedimentary organic matter (SOM) in the Yellow Sea (YS) were studied based on the datasets of total organic carbon (TOC), total nitrogen (TN), organic carbon isotopic values (δ13C) and n-alkanes of forty-seven surface sediment samples. The spatial pattern of TOC and TN coincided with that of the sediment grain size, suggesting the hydrodynamic constraints on the accumulation of SOM in the YS. The relatively low TOC/TN ratios with contrasting TN intercept of the regression lines indicate the influence of the sorption of inorganic N in the NYS and a mixture of microorganism-derived N-rich OM pool with the terrigenous N-poor OM for the SYS sediment samples, respectively. The enriched δ13C could also be partially related to the agriculture inputs due to the enhanced fertilization process in addition to the planktonic-derived OM. Molecular compositions of n-alkanes and principal component analysis (PCA) showed a significant terrigenous contribution for the SOM in the central mud deposits. The observed even carbon preference of the short chain length n-alkanes (C12–C22) reveals the potential contribution of microorganism-derived OM in the YS. Combined lines of evidence of significant terrigenous n-alkanes in the YS suggest that the hydrodynamic forcing plays a key role on the selective dispersal and preferential accumulation of the fluvial terrigenous organic materials. The simplified terrigenous SOM transport pathway to the central mud deposits of the YS was conceptually constructed based on the mixed sediments provenances, hydrodynamic transport and depositional mechanism of the fine-grained sediments in this region.

► The YS central mud deposits are evident for the presence of terrigenous n-alkanes.
► Microorganism-derived OM was related to the even carbon preference of LMW n-alkanes.
► Hydrodynamics constrains on the selective dispersal and fate of terrigenous SOM.
► Terrigenous SOM transport pathway to the central mud was conceptually constructed.