Biomarker record in the Hupo Trough of the southwestern East Sea since the late Pleistocene

The East Sea, located on the northwest continental margin of the Pacific Ocean, acts an important marine environment sensitive to the global/regional climate change including the East Asian monsoon. GDGT (glycerol dialkyl glycerol tetraether), one of the membrane lipids originated from archaea or bacteria, has been broadly used as a ubiquitous biomarker for the paleoceanogprahic reconstruction. Although the numerous paleoceanographic results in the East Sea have been reported, the GDGT records and its application to the East Sea paleoceanography are still limited. In this study, we reconstructed the late Pleistocene seawater temperatures using hydroxylated and isoprenoid GDGTs using a sediment core 19ESDP-101 from the Hupo Trough of the southwestern East Sea (Japan Sea). Several temperature proxies were compared, alongside additional GDGT-derived indices and mean grain size. The temperature proxies yielded broadly consistent temperatures during the warm periods, but diverged in cooler intervals, where RI-OH′ values decreased sharply. These discrepancies reflect the different sensitivity to temperature, salinity, and depositional conditions. Proxy-derived temperatures were inversely correlated with sediment grain size, implying linkage between hydrographic and depositional environments. During the glacial periods, coarse-grained particles, low TEX₈₆L values, and high terrestrial input were correlated, suggesting the sea-level control on environmental conditions. Nevertheless, the integration of multiple GDGT proxies from core 19ESDP-101 highlights the significance of local oceanographic settings in paleoenvironmental reconstruction and supports the selective use of TEX₈₆L and OH-GDGTs.