Response of chironomid assemblages to East Asian summer monsoon precipitation variability in northern China since the last deglaciation.

ABSTRACT We investigate chironomid assemblages in a sediment core from Gonghai Lake, which is located on the East Asian summer monsoon (EASM) boundary in northern China, to quantify EASM variability during the past 13.5 ka BP. Six significantly different chironomid assemblage zones indicate that maximum precipitation and water depth occurred in the mid-Holocene (8270-2700 cal a BP) and the minimum period was the past 1250 years. A modern dataset of 44 lakes near Gonghai Lake was sampled to calibrate the response of chironomid assemblages to precipitation. Our results demonstrate that mean annual precipitation is the most significant environmental variable influencing modern chironomid assemblages in this monsoonal region. Maximum EASM precipitation in the mid-Holocene, indicated by chironomid assemblages in the monsoon fringe, contrasts with the early Holocene EASM maximum suggested by stalagmite δ¹⁸O data from southern China, but is consistent with other evidence. Our findings are compatible with the proposal that the stalagmite δ¹⁸O variations in southern China may not reliably reflect the evolution of EASM since the last deglaciation. [ABSTRACT FROM AUTHOR]