Intrusion of Circumpolar Deep Water has driven the Holocene changes in diatom- and dinoflagellate-derived productivity at Palmer Deep, Western Antarctic Peninsula

The western Antarctic Peninsula, one of the world's most rapidly warming regions, has undergone substantial ecosystem changes, including community succession driven by environmental stress. However, due to the lack of suitable proxies, how this succession responded to Holocene climate fluctuations remains unknown. This study focuses on a sediment core from Ocean Drilling Program (ODP) Leg 178 Site 1098, Palmer Deep, western Antarctic Peninsula, a hotspot of biological activity and a core area of long-term ecosystem research. By analyzing lipid biomarkers (sterols, n -alkanols, phytol, and fatty acids) and other proxies throughout the Holocene, this study aims to determine the past changes in productivity and the contributions of different phytoplankton groups. Lipid biomarkers (e.g., brassicasterol, sitosterol, phytol, and 16:0 fatty acid) generally aligned with variations in diatom abundance and stable carbon isotope of organic carbon (δ 13 C org ), indicating an overall trend of the diatom-dominating productivity that was mainly influenced by Circumpolar Deep Water (CDW) intrusion, along with other oceanic factors. The changes in dinosterol, however, indicated stable or even increased dinoflagellate-associated productivity during cool climates of the early Holocene and Neoglacial, concurrent with reduced diatom-associated productivity. This study highlights the advanced applicability of lipid biomarkers in reconstructing productivity changes across multiple components of phytoplankton communities, which provide a powerful tool for revealing the evolution of Antarctic marine ecosystems under climate change impacts. • Lipid biomarkers are powerful for revealing climatic impacts on multiple biotic components. • Increased dinoflagellate productivity during cool climates of early Holocene and Neoglacial. • Opposite trend of dinoflagellate and diatom productivity during cool periods. • Holocene productivity mainly influenced by westerly-driven CDW intrusion.