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首页> 外文期刊>Palaeogeography, Palaeoclimatology, Palaeoecology: An International Journal for the Geo-Sciences >Monospecific planktonic diatom assemblages in the Paleo-Kathmandu Lake during the middle Brunhes Chron: Implications for the paradox of the plankton
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Monospecific planktonic diatom assemblages in the Paleo-Kathmandu Lake during the middle Brunhes Chron: Implications for the paradox of the plankton

机译：Brunhes年代中期古加德满都湖中的单特异性浮游硅藻组合：对浮游生物悖论的启示

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摘要

The almost monospecific assemblages of planktonic diatoms that occurred in ancient lakes during the middle Brunhes Chron are an important research issue for lake ecosystems because their existence implies that the famous paradox of the plankton was no paradox at that time. To investigate their cause, I examined the assemblage structure and diversity of planktonic diatoms in the Paleo-Kathmandu Lake at Nepal Himalaya over the past 600. kyr. The assemblage structure changes frequently after 300. ka but remains nearly stable before then. Additionally, planktonic species show a relatively high average diversity after 300. ka but show an extremely low average before then. Those abnormal ecological conditions before 300. ka reflect the formation of almost monospecific planktonic diatom assemblages of Cyclotella kathmanduensis and Puncticulata versiformis. The assemblage structure and species diversity of the planktonic diatoms were controlled by lake-level fluctuations (especially lake-level declines) as ecological disturbances. After 300. ka, fluctuations in lake levels occur in about 20. ka intervals, which probably helped to sustain diverse planktonic diatom assemblages. In contrast, much longer intervals occurred between lake-level fluctuations before 300. ka, and these were of a frequency that was too low to sustain diverse planktonic diatom assemblages. This may have allowed C. kathmanduensis and P. versiformis to form monospecific assemblages.
机译：在Brunhes Chron中段的古代湖泊中发生的浮游硅藻几乎是单特异性的组合，对于湖泊生态系统来说是一个重要的研究课题，因为它们的存在暗示着当时著名的浮游生物悖论还不是悖论。为了研究它们的成因，我研究了过去600年来尼泊尔喜马拉雅山古加德满都湖中浮游硅藻的组成结构和多样性。组装结构在300 ka之后频繁变化，但在此之前几乎保持稳定。此外，浮游物种在300 ka之后显示出相对较高的平均多样性，但在此之前显示出极低的平均值。 300. ka之前的那些异常生态条件反映了加德满都小环周菌和凡士林的单种浮游性硅藻组合的形成。浮游硅藻的组成结构和物种多样性受到作为生态干扰的湖面涨落（尤其是湖面下降）的控制。在300. ka之后，湖泊水位的波动大约在20. ka间隔内发生，这可能有助于维持各种浮游硅藻组合。相反，在300. ka之前，湖级波动之间的间隔要长得多，而且这些间隔的频率太低，无法承受各种浮游硅藻的聚集。这可能已经允许加德满都C. and P. versiformis形成单特异性组合。

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