Monospecific planktonic diatom assemblages in the Paleo-Kathmandu Lake during the middle Brunhes Chron: Implications for the paradox of the plankton
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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DOI：
10.1016/j.palaeo.2010.12.007
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发表时间：
2011-02
期刊：
影响因子：
--
通讯作者：
Tatsuya Hayashi
中科院分区：
文献类型：
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作者：
Tatsuya Hayashi
在Brunhes Chron中期的古湖泊中出现的几乎单种的浮游硅藻组合是湖泊生态系统的一个重要研究问题，因为它们的存在意味着著名的浮游生物悖论在当时并不矛盾。为了探讨其原因，我检查了过去600 kyr在尼泊尔喜马拉雅山古加德满都湖浮游硅藻的组合结构和多样性。组合结构在300ka后变化频繁，但在此之前基本保持稳定。此外，300ka后，南极物种的平均多样性相对较高，但在此之前，物种的平均多样性极低。300ka前的异常生态条件反映了加德满都小环藻和变形斑藻几乎单一种的浮游硅藻组合的形成。湖泊水位波动（尤其是水位下降）作为生态扰动，控制着浮游硅藻的群落结构和物种多样性。300ka后，湖平面的波动发生在约20ka的时间间隔，这可能有助于维持多样的浮游硅藻组合。相比之下，更长的时间间隔发生在300万年前的湖泊水位波动，这些是一个频率太低，以维持不同的浮游硅藻组合。这可能使C。kathmanduensis和P.versiformis组成单种组合。
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 600kyr. The assemblage structure changes frequently after 300ka but remains nearly stable before then. Additionally, planktonic species show a relatively high average diversity after 300ka but show an extremely low average before then. Those abnormal ecological conditions before 300ka 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 300ka, fluctuations in lake levels occur in about 20ka intervals, which probably helped to sustain diverse planktonic diatom assemblages. In contrast, much longer intervals occurred between lake-level fluctuations before 300ka, 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.