翡翠水庫病毒豐度之時空變化

Abstract

為了解亞熱帶(半)封閉性淡水系統內病毒豐度的時空變化及其對微生物環的影響，本研究從2004年11月至次年11月間，於翡翠水庫大壩站進行為期一年的週採樣，利用螢光計數法及穿透式電子顯微鏡法來推估病毒豐度的時空變異及對潛在宿主的致死率。其它的調查參數包括水體中細菌豐度(0.5~8.9×106 cells ml-1)、細菌生產力(1.1~118.3 mgC m-3 d-1)、藍綠菌豐度(0.3~16.0×105 cells ml-1)、葉綠素濃度(0.0~7.0 μg l-1)及相關的物化參數。結果發現，翡翠水庫病毒的豐度測值在0.3~7.2×107 particles ml-1之間。空間分佈上，病毒豐度由表水往底水遞減，但接近底泥時有增高的趨勢；時間變異上，表水層的病毒豐度有明顯季節性變化：夏、秋高(1.6~6.4×107 particles ml-1) ，春、冬低(0.8~3.9×107 particles ml-1)；中水層的病毒豐度不具明顯變化趨勢；底水層的病毒豐度雖呈現季節性變化，但起伏較表水層大。颱風造成的無機營養鹽(磷酸鹽)脈衝，對於病毒豐度似有提升的效應。從表水層的資料得知：病毒豐度與細菌、藍綠菌豐度及水溫均呈正相關，而細菌及藍綠菌豐度又與水溫呈正相關。穿透式電子顯微鏡觀察所得的數據卻指出，病毒裂解效應僅佔細菌死亡率的8 %，並非細菌主要的致死因子。但是表水層的病毒-細菌商數與細菌豐度仍呈顯著的負相關顯示，除了原生動物捕食作用之外，病毒也是調節表水層細菌豐度季節性變化的原因之一。

To estimate the temporal and vertical distribution of viral abundance (VA) and understand its roles play in the microbial loop in a subtropical (semi-) closed freshwater ecosystem, VA and its infection rate on bacterioplankton were studies weekly from November 2004 to November 2005 in the Fei-Tsui Reservoir. Heterotrophic bacterial abundance (BA, 0.5 to 8.9×106 cells ml-1), heterotrophic bacterial production (BP, 1.1 to 118.3 mgC m-3 d-1), cyanobacterial abundance (CA, 0.3 to 16.0×105 cells ml-1), chlorophyll a concentration (Chl, 0.0 to 7.0 μg l-1) and other physic-chemical parameters were also measured. VA ranged from 0.3 to 7.2×107 particles ml-1. For vertical variation, VA decreased with depth, and then reached highest values near the bottom. VA in the epilimnion show a strong seasonal trend with the highest abundance (1.6~6.4×107 particles ml-1) in the summer/autumn and lowest values (0.8~3.9×107 particles ml-1) in the spring/winter. On the other hand, VA observed in the metalimnion showed no specific trend. VA in the hypolimnion did show a seasonal pattern, but with a higher magnitude of fluctuation than that in the epilimnion. N nutrient pulses induced by typhoons seemed had effects in enhancing. VA were positively correlated with temperature, BA and CA, while BA and CA were also showed a positive correlation with temperature. Viral lysis (determined by the ratio of viral-containing bacteria) rate was low with values<8%, indicating that VA might not be the cause for bacteria mortality. There was a negative liner regression(r = -0.43，p<0.05) between virus-bacterium quotient and BA. This indicated that except for the protozoa grazing effect, viral lysis may be a low but constant factor in regulating seasonal variation of BA in this reservoir.