Ecological variations in diatom assemblages in the Paleo-Kathmandu Lake linked with global and Indian monsoon climate changes for the last 600,000 years
Ecological variations in diatom assemblages in the Paleo-Kathmandu Lake linked with global and Indian monsoon climate changes for the last 600,000 years
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DOI：
10.1016/j.yqres.2009.07.003
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发表时间：
2009-11
影响因子：
2.3
通讯作者：
Tatsuya Hayashi;Y. Tanimura;Y. Kuwahara;M. Ohno;M. Mampuku;R. Fujii;H. Sakai;T. Yamanaka;T. Maki;M. Uchida;Wataru Yahagi;H. Sakai
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文献类型：
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作者：
Tatsuya Hayashi;Y. Tanimura;Y. Kuwahara;M. Ohno;M. Mampuku;R. Fujii;H. Sakai;T. Yamanaka;T. Maki;M. Uchida;Wataru Yahagi;H. Sakai
利用在尼泊尔喜马拉雅加德满都盆地钻探的古湖泊(古加德满都湖)沉积物，研究了近60万年来硅藻化石组合的变化及其与全球和印度季风气候变化的关系。通过将花粉干湿指数记录与SPECMAPδ18O叠加记录进行调谐，建立了岩心的年表。生物硅含量和硅藻化石组合的研究表明，在冰期和间冰期尺度上，硅藻组合的生产力和组成的变化与全球和印度季风气候变化密切相关。当夏季季风降雨量在间冰期(间歇期)增加时，由于陆地营养物质输入湖泊的增加，硅藻生产力增加。当冰期(冰期)夏季风降水减少和/或冬季季风干旱化加强时，硅藻的生产力下降，湖平面下降导致硅藻组合的组成发生变化。独特的加德满都环藻和垂尾环藻的单种组合出现在约590-390年间。这可能归因于硅藻组合的进化微调，以适应特定的湖泊环境条件。此外，季风气候的低幅度进动变化和较少的湖泊水位变化也可能使这两个物种在较长时间内占据主导地位。
Variations in fossil diatom assemblages and their relationship with global and Indian monsoon climate changes for the last 600,000 yr were investigated using a core of ancient lake (Paleo-Kathmandu Lake) sediments drilled at the Kathmandu Basin, Nepal Himalaya. Chronological scales of the core were constructed by tuning pollen wet and dry index records to the SPECMAP δ18O stack record. Examinations of biogenic silica contents and fossil diatom assemblages revealed that variations in productivity and compositions of diatom assemblages were closely linked with global and Indian monsoon climate changes on glacial and interglacial time scales. When summer monsoonal rainfall increased during interglacials (interstadials), diatom productivity increased because of increased inputs of terrestrial nutrients into the lake. When summer monsoonal rainfall reduced and/or winter monsoonal aridification enhanced during glacials (stadials), productivity of the diatoms decreased and lake-level falling brought about changes in compositions of diatom assemblages. Monospecific assemblages by unique Cyclotella kathmanduensis and Puncticulata versiformis appeared during about 590 to 390 ka. This might be attributed to evolutionary fine-tuning of diatom assemblages to specific lake environmental conditions. Additionally, low-amplitude precessional variations in monsoon climate and less lake-level changes may have also allowed both species to dominate over the long periods.