碩士 / 國立彰化師範大學 / 生物學系 / 91 / In this study, the diatom assemblages in the core BLX-C from Boston Lake inferred to the paleoecological history of Boston Lake area. Samples were collecting at 4-8 cm intervals from core BLX-C (7m). One hundred and seventy-one samples from the core BLX-C were proceeded for diatom analysis. The core BLX-C was used to infer the paleoclimate over the past 8,000 yrs and the average sedimentation rate was 0.096 cm / year. A total of 39 genera and 206 species of diatom were found from this core. Among them, freshwater genera, such as Achnanthes、Amphora、Cyclotella、Fragilaria、Navicula、Pseudostaurosira、Staurosira and Staurosirella, were dominant in the whole core. On the other hand, the diatom abundance was ranged from 1.67 ×106 to 1.08 ×108 vales/g DW having an average of 3.29 ×107 vales/g DW. However, the fluctuations among the amount of genus, species and the value of species diversity index were 9-25, 16-62 and 2.19-4.73, respectively. In addition, based on the results of diatom abundance, magnetic susceptibility and the percentage of aragonite and calcite, four distinct stages of climate change were recognized as follow: (1) unstable warm climate between 7.9 and 4.5 ka BP (depth 712-580 cm); (2) fluctuating climates alternation between moderate aridity and wetness during 4.5 and 1.6 ka BP (depth 580-280 cm); (3) extreme wetness period between 1.6 and 0.7 ka BP (depth 280-38 cm) and (4) cold , humid climate between 0.7 and 0.6 ka BP (depth 38-2 cm). At the same time, analyzing the indicator species of the pH, salinity and nutrient level among the diatom assemblage of the four climate stages indicated that the water quality of Boston Lake was affected by the water quality. Generally, the characteristics of the Bosten Lake water had lower pH value, lower salinity and higher nutrient level in warm and wet period, while opposite in cold and dry period. Furthermore, the fluctuations of diatom indicated species were closely related to the mineral components (including aragonite and calcite), total organic carbonates and gastropod fossils. From the fluctuations of diatom indicated species, the increasing of water quantity of Boston Lake during 5.7-4.3 and 3.1-1.5 ka BP was speculatively from the input of run-off and the increasing of atmosphere relative humidity. In contrast, during 1.5-0.8 ka BP, the decreasing of water quantity of Boston Lake was speculatively due to the increasing of water evaporation in the lake surface. In conclusion, from the investigation of diatom assemblage in the whole core, we can realize that the hydrology and lake level of Boston Lake in the past was mainly influenced by paleoecological climate pattern (eq. air temperature and humidity).
| Identifer | oai:union.ndltd.org:TW/091NCUE0112003 |
| Date | January 2003 |
| Creators | Jing-Chieh Ho, 何盈潔 |
| Contributors | Wei-Lung Wang, 王瑋龍 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 123 |
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