末次冰盛期以来日本海浮游植物生产力和群落结构变化

The Changes of Phytoplanktonic Productivity and Community Structure in the Japan Sea Since the Last Glacial Maximum

生物标志物法已经被广泛应用于重建海洋浮游植物生产力和群落结构变化。本文利用这种方法重建了日本海末次冰盛期以来浮游植物生产力和群落结构变化。结果显示,生物标志物含量在末次冰期最盛期21～19 ka和14～4 ka时有高值,而在19～14 ka、4～0 ka有低值。末次冰期最盛期时生物标志物的高含量是由于分层导致的底层水缺氧,生物标志物得到较好保存的结果,而此时日本海盐度很低,使颗石藻相对含量很低;19～14 ka陆源输入减少,日本海生产力水平较低,不断增加的盐度使浮游植物群落结构由硅藻、甲藻占优转变为颗石藻占优;14～4 ka对马暖流流量的加大提高了日本海的初级生产力,同时高营养盐利于硅藻、甲藻的生长,使颗石藻的相对比例减小;4 ka以后随冬季风的增强和黑潮减弱,对马暖流减弱,供应的营养盐减少,日本海生产力水平降低,使颗石藻的相对比例增大,硅藻、甲藻的相对比例减小。

Biomarkers have been applied for the reconstruction of phytoplankton productivity and community structure. In this study, the changes of phytoplankton productivity and community structure since the last glacial maximum（LGM） in the Japan Sea were reconstructed by multi-biomarkers. The results indicated that the contents of biomarkers had higher values during the LGM（21-19 ka） and the last 14-4 ka, and had the lower values during the last 19- 14 ka and 4 ka. The high contents of biomarkers during the LGM were caused by better preservation of biomarkers due to strong stratification and anoxic conditions in the bottom waters, while low salinity led to less coccolithophore contribution at this time. During the last 19-14 ka, the reduced primary productivity in the Japan Sea was associated with the decreased terrestrial input, when the increased salinity resulted in the diatom and dinoflagellate contributions decreased while coccolithophore contribution increased. During the last 14-4 ka, primary productivity elevated due to the enhanced flux of Tsushima warm current, and the abundant nutrient supply from the Tsushima warm current favored diatoms and dinoflagellates competition and decreased the contribution from coccolithophore. During the last 4 ka, the Weakened Tsushima warm current owing to the increased winter monsoon and the suppression of the Kuroshio Current caused the reduction of primary productivity, the decrease of diatom and dinoflagellate contributlons, and the increase of coccolithophore contribution.