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Seasonal variations of viral - and nanoflagellate - mediated mortality of heterotrophic bacteria in the coastal ecosystem of subtropical western Pacific
|Authors: ||Jie Hung|
|Contributors: ||NTOU:Institute of Marine Environmental Chemistry and Ecology|
|Issue Date: ||2013-10-07T02:53:26Z
|Abstract: ||水體中異營性細菌被病毒裂解或微細鞭毛蟲攝食之相對重要性，對於食物網能量傳遞有著不同的影響。本研究實驗是利用修正過後的稀釋培養法於2011 年4 月至12 月及2012 年4 月至10 月期間估算病毒裂解與微細鞭毛蟲攝食對細菌死亡率所造成的影響。研究期間細菌成長率變化為0.078 h-1 (2011 年四月) 至0.42 h-1 (2011 年九月)，並顯示溫度是控制細菌季節性成長率變化之重要因子。此外，微細鞭毛蟲攝食和病毒裂解移除細菌生產量之季節變化各為34 %至68 %及13 %至138 %之間。本研究認為在夏季(特別於7－8 月間)，由於有較多的微細鞭毛蟲數量，使得控制細菌生產量的主要因素為攝食作用，並超越病毒裂解的影響。另一方面，病毒裂解被認為是9 月至12 月間主要的細菌生產力移除作用。基於這些研究結果，觀察到本研究海域細菌數量之季節性變化可以利用成長率與被移除率(攝食率＋裂解率)來解釋。|
Since viral lysis and nanoflagellate grazing differ in their impact on the aquatic food web, it is important to assess the relative importance of both bacterial mortality factors. In this study, an adapted version of the modified dilution method was applied to simultaneously estimate the impact of both viral and nanoflagellate grazing on the mortality of heterotrophic bacteria. A series of experiments was conducted monthly from April to December 2011 and April to October 2012. The growth rates of bacteria were measured and ranged from 0.078 h-1 (April 2011) to 0.42 h-1 (September 2011).Results also suggest that temperature can be important in controlling the seasonal variations of bacterial growth. Furthermore, it appeared that seasonal changes in nanoflagellate grazing and viral lysis could account for 34% to 68% and 13% to 138% of the daily removal of bacterial production, respectively. We are suggesting that nanoflagellates grazing could play a key role in controlling bacterial biomass and might exceed the impact of viral lysis during summer period (July to August), because of the higher abundance of nanoflagellates. On the other hand, viral lysis was identified as the main bacterial mortality cause between September and December. Based on these findings in this study, the observed seasonal variations in bacterial abundance can be explained by the following scenario in which both growth rates and loss rates (grazing + viral lysis) influence the dynamics of the bacteria community.
|Appears in Collections:||[海洋環境與生態研究所] 博碩士論文|
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