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|Title: ||副熱帶陸棚水體生態系微細鞭毛蟲對細菌浮游生物攝食壓的研究－ 細菌空間變動及微生物食物網能量傳遞|
Coupling of the Spatial Dynamic of Bacteria and Nanoflagellate Grazing Pressure and Carbon Flow of the Microbial Food Web in the Subtropical Pelagic Continental Shelf Ecosystem
|Authors: ||Pei-Jung Tsai|
|Contributors: ||NTOU:Institute of Marine Environmental Chemistry and Ecology|
|Issue Date: ||2013-10-07T02:53:18Z
|Abstract: ||為瞭解細菌浮游生物(異營細菌與藍綠細菌)在副熱帶陸棚水體生態系中小範圍數量分布，與造成此種空間變動之成因，並同時推估細菌浮游生物在微生物食物網中向上傳遞情況。本實驗於2010與2011夏季在東海南部海域使用海研二號以分割過濾法進行五次實驗。由溫鹽圖(T-S diagram)得知五次實驗期間本海域表層均被高溫低鹽之台灣暖流水所占據。實驗結果顯示異營細菌成長率與溫度呈現負相關，暗示底層低溫湧昇水帶入之營養鹽，會刺激異營細菌成長。因此本研究海域屬BU (Bottom-up Control)控制，由此推測貧營養生態系當營養鹽注入時，會由TP (Top-down Control)變成BU。湧昇帶入之營養鹽會使細菌成長，當異營細菌與藍綠細菌現存量較低時淨成長率為正，反之現存量較高則淨成長會負值。因此造成異營細菌數量(105-106 cells ml-1)和藍綠細菌數量(104-105 cells ml-1)均在一狹窄範圍內變動，形成一個Predator-prey eddy或 Predator-prey oscillations。 發現異營細菌和藍綠細菌的成長量與被攝食量有明顯的正相關，細菌62%成長量會經由微細鞭毛蟲攝食向上傳遞，而藍綠細菌為55%。但被攝食量經由連續分割法證實有瀑布效應(cascading effect)存在，因此異營細菌被微細鞭毛蟲攝食量大約低估28.3%，藍綠細菌大約34.6%。由此可知此九成以上成長量會經由微細鞭毛蟲攝食向上傳遞。微細鞭毛蟲每日所攝食之能量64%來自異營細菌，36%來自藍綠細菌。|
To investigate the mechanism of temporal and spatial dynamic of bacteria community (bacteria and Synechococcus spp.) and to estimate the carbon flux in the microbial food web in the subtropical continental shelf pelagic ecosystem, we conducted size-fractionation experiments in 5 cruises of R/V Ocean Research II during the summer periods of 2010 and 2011 in the southern East China Sea. Our culture experiment was done in surface water which was characterized with oligotrophic Taiwan Strait Water during our study period according to the temperature-salinity (T–S) diagram. Bacteria growth rate shows a negative correlation with temperature, indicating that the active growth of heterotrophic bacteria might be induced by nutrient brought up by the cold upwelling water. It is therefore evident that our studied area belongs to a BU control pelagic ecosystem. We suggest that the microbial food web of an oligotrophic ecosystem may be changed from top-down control to resource supply (bottom-up control) with the presence of a physical force to bring nutrient into the oligotrophic ecosystem. Upwelling brings nutrient-rich water to euphotic zone, and promotes bacteria growth, then the higher consumption rate of nanoflagellate will be enhanced due to increased biomass. The net growth rate (growth rate–grazing rate) becomes negative when the density of bacteria and Synechococcus spp. is lower than the threshold value. The interaction of growth and grazing will limit the abundance of bacteria (105-106 cells ml-1) and Synechococcus spp. (104-105 cells ml-1) within a narrow range, forming a predator-prey eddy or predator-prey oscillations. Meanwhile, 62% of bacteria production and 55% of Synechococcus spp. production are transported to higher trophic level (nanoflagellate), both transported percentages of carbon could be underestimated as a result from the cascading effect. Based on the result of increasing number of sizes in the size-fractionation experiments, we estimated that the predation values were be underestimated 28.3% in bacteria and 34.6% in Synechococcus spp. From the corrected result, we conclude that over 90% of picoplankton production was transferred to high trophic level via nanoflagellate in microbial food web and the diet of nanoflagellate is composed of 64% of bacteria and 36% of Synechococcus spp .
|Appears in Collections:||[海洋環境與生態研究所] 博碩士論文|
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