博士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 93 / Abstract
We analyzed seasonal and diel fluctuation patterns of heterotophic bacteria, Synechococcus spp., and nanoflagellates at a coastal station in the northeast of Taiwan between July 1999 and September 2003. All of these organic exhibited a clear seasonal cycle, with high values during the warm seasons (June to October) and lower values during the cold seasons (November to May). Synechococcus spp. and nanoflagellates exhibited diel fluctuation at water temperatures above 25°C. Cell concentrations of Synechococcus spp. were significantly higher during the evening, whereas those of nanoflagellates were higher during the day. The day and night amounts of heterotrophic bacteria did not differ significantly, and we did not observe diel rhythms of these organisms below 25°C. The fractionation experiments we performed between between August 2002 and July 2003. In the subtropical coastal ecosystem, a two-phased (warm>25℃, cold <25℃) seasonal cycle with a 10-fold variation was found in the picoplankton growth and grazing rate. The only exception was the grazing rate of Synechococcus (2-5 fold). A significant diel cycle of picoplankton growth and grazing rates existed during the warm season with both rates in bacteria being day＞night while, in contrast, Synechococcus was night＞day. During the warm season, our study clearly indicate that nanoflagellates largely depend on bacteria as an energy source in the daytime, but about Synechococcus contributed about 82% of the nanoflagellate diet at night. Another, in the warm season, naoflagellates consumed equal proportions of bacteria and Synechococcus spp. production; therefore, both consumption processes have an equal significance in warm season. However, during the cold season, bacteria contributed about 81% of the nanoflagellate diet, making it a more important food source than Synechococcus.
For studying the control factors of diel variations in Synechococcus abundance during the warm season, to use culture experiment with different density of Synechococcus and Frequency of Dividing Cell method to measure the variations of grazing and growth, and build the model by this method. For the results of model, the grazing rates of nanoflagellates are positively correlated with Synechococcus abundance, it mean that nanoflagellate grazing rates were likely to increase with Synechococcus abundance. Another, temperature could control the growth of Synechococcus, by this reason, we know that nanoflagellates grazing rates were likely to increase at night after Synechococcus had peak, and removed the Synechococcus abundance quickly.
| Identifer | oai:union.ndltd.org:TW/093NTOU5451022 |
| Date | January 2005 |
| Creators | An-Yi Tsai, 蔡安益 |
| Contributors | Kuo-Ping Chiang, 蔣國平 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 114 |
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