Sources and preservation of sedimentary organic matter in the Southern Bohai Sea and the Yellow Sea: Evidence from lipid biomarkers

•The Yellow River runoff is the predominant source of the terrestrial OM.•Sediment process plays a significant role in distribution and preservation of OM.•Inconsistent degradations between the different terrestrial lipids were observed.

The region of Southern Bohai Sea (SBS) and Yellow Sea (YS) represents one of the best examples of large river-dominated ocean margins. The transport and accumulation of sediments played a primary role in distribution of the lipids in the region and could lead to a preferential accumulation of these more refractory land-based lipids. The spatial distribution of total organic carbon (TOC) matched with the lipid distributions over the shelf, and high TOC presented in the central YS, but TOC burial fluxes decreased from 110 ton/km2/yr of SBS to 25-32 ton/km2/yr of YS. Good correlations were observed between terrestrial n-alkanes and TOC in the sediments of SBS and northern YS, but they were poor for southern YS, meanwhile higher ratios of nC27 + nC29 + nC31/nC15 + nC17 + nC19 (12 ± 6) were observed in SBS, and lower in YS (2.2 ± 1.0), suggesting the Yellow River discharge was an important source of terrestrial organic matter to the shelf.