2009—2010年南海北部浮游有孔虫通量和稳定同位素季节变化及其对东亚季风的响应

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

通过对南海北部2009—2010年获得的浅层、中层和深层时间系列沉积物捕获器的样品分析,发现浮游有孔虫总通量和主要属种Globigerinoidesruber,Globigerinoidessacculifer,Pulleniatinaobliquiloculata和Neogloboquadrinadutertrei的通量和百分含量存在明显的季节性变化,在东北季风和西南季风盛行期出现高值,特别在冬季风期间高值明显,在季风间歇期出现低值,展示出"双峰型"通量模式。浮游有孔虫通量与颗粒总通量、有机碳通量、总碳通量、总氮通量、碳酸钙通量和蛋白石通量变化一致,随叶绿素a浓度和风速大小变化而改变,表明南海北部生源颗粒通量主要受季风影响的表层生产力所控制。浮游有孔虫壳体氧同位素与表层海水温度的季节变化相吻合。壳体δ18 O主要受海水温度变化的影响,不同深度属种的δ18 O变化反映了上层海水温度梯度。此外,壳体碳同位素值总体上在东亚季风强盛期低、季风间期高,与表层海水中叶绿素a浓度和海表风速的变化趋势相反,说明浮游有孔虫δ13 C值反映了水体营养和表层生产力的变化。

Based on the analysis of the time-series samples obtained from the shallow, middle and deep sedi- ment traps in the northern South China Sea from July 2009 to May 2010, it is found that the flux of the to-tal planktonic foraminiferal tests（shells）, and the flux and percentage of the primary species Globigeri-noides ruber , Globigerinoides sacculi f er , 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 pri-marily controlled by the surface productivity affected by the monsoon. The seasonal δ180 variation in plank- tonic 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 wa- ter.