Seasonal distribution of planktic foraminifers in the East Sea (Sea of Japan), a large marginal sea of the northwest Pacific

Abstract

A time series sediment trap was deployed in the interior of the East Sea (Sea of Japan) (39 degrees 40'N, 132 degrees 24'E) for the period from July 1994 to July 1995, Total foraminifera flux varied from 3 to 8,200 individuals/m(2)/day, with major peaks during late fall (November) rind winter (December and January), and a minor peak curing spring (March-May), Foraminiferal assemblages were dominated by both right- and left-coiled Neogloboquadrina pachyderma, N. dutertrei, and Globigerina bulloides, and their fluxes varied seasonally, The highest flux of both right- and left-coiled N. pachyderma throughout all seasons indicates that the study site was dominated by the cold Subarctic water mass. The influx from the cold North Korean Current was stronger than that of the warm Tsushima Current in the spring. This cold water influx is evidenced by the highest flux of left coded N. pachyderma and Globigerina bulloides, and the absence of N. dutertrei. The dominance of right-coiled N. pachyderma during January, July, and November-December suggests a greater influence of the warm Tsushima Current. The absence of N. dutertrei at the study site and the presence of N. dutertrei in the North Pacific in spring suggests that the study site in the Japan Basin is isolated from the North Pacific Ocean during the spring. G. bulloides and N. dutertrei dominate during March and November, respectively. The onset of the winter monsoon (late October-November) is responsible for the planktic foraminifera flux peak during November.