THE INFLUENCE OF EAST ASIAN MONSOON ON SEASONAL VARIATIONS IN PLANKTONIC FORAMINIFERAL FLUX AND STABLE ISOTOPE IN THE NORTHERN SOUTH CHINA SEA DURING 2009-2010

Based on the analysis of the time-series samples obtained from the shallow, middle and deep sediment traps in the northern South China Sea from July 2009 to May 2010, it is found that the flux of the total planktonic foraminiferal tests(shells), and the flux and percentage of the primary species Globigerinoides ruber, Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei are characterized by apparent seasonal variation.Their higher values appeared in the prevailing northeast and southwest East Asian Monsoon periods, especially in the winter monsoon time, and lower values appeared in intermittent period of the East Asian Monsoon, which performed a "bimodal pattern" flux model. Their seasonal variations are in line with the change in total particle flux, organic carbon flux, total nitrogen flux, calcium carbonate flux and opal fluxes, and all are closely related to the alteration of chlorophyll-a concentrations and wind speed,indicating that the biogenic particle flux in northern South China Sea is primarily controlled by the surface productivity affected by the monsoon.The seasonal δ¹⁸O variation in planktonic foraminiferal tests is in conformity with the seasonal changes in sea temperature.The variations in species dwelled in different depth reflected the temperature gradient of the upper ocean.The δ¹³C variations of planktonic foraminiferal tests generally performed lower values in the prevailing East Asian Monsoon periods and higher values in the monsoon intermittent time, showing an opposite variation trend with the chlorophyll-a concentrations and wind speed of the surface water.It demonstrates that the δ¹³C value of the planktonic foraminiferal tests reflected the variation in nutrition or primary productivity of the ocean water.