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Effects of temperature change on seasonal variations in bacterial growth and loss rates in the northeast of Taiwan
|Authors: ||Hsiao, Wei|
Global warming;marine food webs;temperatures;bacterial growth and mortality
|Issue Date: ||2017-11-15T08:45:39Z
|Abstract: ||二十一世紀正是人類生存在全球變遷的時代，如果全球變遷未能獲得有效的控制，將導致整個地球氣候以及海洋循環的改變。然而海洋生態系食物鏈運轉過程中各食物階層對全球變遷的反應程度為何?目前仍尚未有具體的答案。在一般水域生態系統中，細菌是溶解性有機碳的主要消耗者，且扮演著調節有機碳的生地化循環之重要角色。因此，細菌被移除過程的方式也影響到水體有機碳的流向，一般而言，原生生物的攝食過程即能將有機碳及能量往上一階食物階層傳遞。而病毒的裂解過程，則會將有機碳及營養鹽快速釋放於水體中，進而促使細菌再次有效利用。因此本研究即要了解在全球變遷海洋暖化過程中，溫度的增加是否會對細菌生產及被移除的能力產生影響？本研究使用modified dilution method培養24小時來量測細菌成長率，細菌被攝食率及被病毒裂解率。本研究分別將實驗組分成兩組，控制組為培養在自然環境溫度，另一組為控溫加熱實驗組（約高於環境溫度3℃）。實驗結果發現現場環境溫度在25℃以下時，其加熱培養組，細菌成長變化與控制組相比較約增加27-200%，而在25℃以上時僅增加8-22%。在細菌被移除能力結果發現，增溫後攝食影響會增加(13-250%)，其攝食速率變化與細菌成長速率改變有關。本研究另發現病毒裂解則不受溫度增加影響，可能是細菌種類組成與培養過程中受到溫度增加而改變，致使病毒感染的專一性無法對細菌立即產生影響。或者微細鞭毛蟲隨溫度增加的攝食量也可能攝食被感染的細菌而對病毒裂解能力造成影響。最後經由實驗結果推測海洋暖化會造成臺灣東北沿岸海域微細鞭毛蟲產生明顯攝食增加，進而控制細菌隨溫度增加的生產量。|
The word is steadily warming and induced global change in 21th century, in turn; the Earth’s climatic system and oceanic water circulation will be affected by global change. However, how global warming will affect the ecosystem of marine food chain and structure is under debate. It is well established that a significant fraction of the total carbon flux in marine food webs passes through heterotrophic bacteria. Thus, the fate of bacterial production has important implications for the ecology of microbial food webs and biogeochemical cycling in these systems. The relative contribution of viruses and grazers to bacterial mortality has important consequences for the processing and transfer of organic matter in the ocean. When bacterial cells are grazed, energy is made available to higher trophic levels, whereas when they are lysed, viruses redirect matter and energy away from higher trophic levels and generate substrates for non-infected bacteria. The goal of this study investigated the effect of rising temperatures on bacterial growth and mortality in coastal waters of the western subtropical Pacific Ocean. To do this, water samples were incubated for 24 h at ambient and experimentally increased temperatures (averages 3℃ higher than in situ values) and analyzed for bacterial growth, grazing and viral lysis using a modified dilution method. The experimental warming conditions were found to cause the ranged from 27 to 200% and 8 to 22% increase in bacterial growth rates compared with in situ situations that above and below 25℃, respectively. Furthermore, the experimental warming conditions also caused a 13-250% increase at which bacteria were being grazed, and showed grazing would increase in parallel with bacterial growth rate in this study. However, there was no significant effect of viral lysis as the temperature increased, under grazing pressure; grazers may preferentially graze virus-infected bacteria possibly changing viral mortality response. Furthermore, under grazing pressure, changes in the bacterial community structure may include the selection of virus-resistant bacteria species. These findings suggest that short-term warming changed the function of the microbial food web by increasing the rates of bacterial production and the bacterial carbon flux to predators in our study environment.
|Appears in Collections:||[海洋環境與生態研究所] 博碩士論文|
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