Pyeongtaek wedand, whose name means "flat swamp", is a wide flat paleo-swamp formed during the early Holocene.The Pyeongtaek wetland is located near the central part of the west coast of the Korean Peninsula, and as it was formed during the early Holocene, this area can be particularly useful for investigating coastal plant community ecological responses to climate change and sea-level fluctuations.In this study, we attempted to reconstruct the Holocene coastal depositional environment of the Pyeongtaek area in response to sea-level changes, based on age-controlled pollen and phytoplanktonic algae records.The East Asian monsoon-controlled coastal area is an open system that experiences an intensive interplay between oceanic and terrestrial processes.The ecological response of sensitive terrestrial ecosystems can provide independent data complementing the almost exclusively marine body of evidence.Therefore, coastal-especially intertidal-ecosystems can provide valuable information on past depositional environmental changes because such systems are very sensitive to environmental changes in the sea-continent interface.From 10400 cal-8000 cal a BP, halophytic Chenopodiaceae pollen and marine dinoflagellates indicate the depositional environment was an intertidal flat.Between 8000 cal and 6000 cal a BP, no marine dinoflagellates and abundant meso-to hypersaline salt marshes of Gramineae, with a later increase of mesosaline marshes of Cyperaceae, indicate a transition from intertidal flat to freshwater swamp.From 6000 cal to 4500 cal a BP, aquatic genera and freshwater algae indicate that the study area completely changed to freshwater swamp.The directional sequence in relative abundance of taxa (maximum percentage of pollen of Chenopodiaceae followed by Gramineae, Cyperaceae, and aquatics) suggests a gradational pattern indicative of marked environmental clines typical of intertidal habitats.