Benthic foraminifera in the Nakdong River Delta (southeast Korea) and their response to middle Holocene climatic change in the coastal environment of the East Asian margin

•Benthic foraminifera in the NRD contain the Marine, Bay, and Opportunistic taxa.•Precipitation and resultant river discharge increased in Korean Peninsula at ∼ 4 ka.•Two small maxima of low oxygen-resistant taxon represent the fluctuated TWC.•Replacement of two species implies the enhanced East Asian winter monsoon at 4.6 ka.