The Yellow Sea is a semi-enclosed marginal sea characterized by strong seasonal stratification and the formation of the Yellow Sea Bottom Cold Water (YSBCW), a key hydrographic feature that shapes regional ecosystem dynamics. Understanding how this hydrographic system structures benthic communities is essential for evaluating ecosystem responses to environmental variability in Pacific Asian marginal seas. Macrobenthic samples were collected from 2021 to 2025 using a Smith–McIntyre grab (0.1 m²) across the offshore Yellow Sea, including the YSBCW region and adjacent waters. Hydrographic parameters were measured using CTD casts, and sediment grain size and organic matter contents (total organic carbon and total nitrogen) were analyzed to assess environmental gradients. Species richness and Shannon diversity increased from the YSBCW region toward coastal and East China Sea waters, while macrobenthic density peaked in transitional zones between the cold-water mass and adjacent warm currents. Multivariate analyses revealed clear spatial segregation of community structure associated with hydrographic and sedimentary gradients. Species composition showed positive associations with bottom temperature and sediment sand content, and negative relationships with water depth, fine sediment fractions, and organic matter concentrations. These results demonstrate that macrobenthic communities in the Yellow Sea are strongly structured by hydrographic gradients linked to the YSBCW, highlighting the role of seasonal water-mass dynamics in regulating benthic ecosystem organization in marginal sea environments. Given ongoing ocean warming and potential alterations in the intensity and spatial extent of the YSBCW, benthic community restructuring may occur under future climate scenarios.

Macrofauna, Yellow Sea, Yellow Sea Bottom Cold Water