南海內波對自營性超微浮游生物24小時週期分布之影響研究

Abstract

本研究主要探討南海內波對自營性超微浮游生物包括Prochlorococcus, Synechococcus 及 Picoeukaryotes之24小時週期分佈之影響。本研究在2012~2013年間在南海有不同物理特性的測點進行了7個24小時週期研究。分別是上舉型內波影響區 (4站)，沉降型內波影響區 (1站)，以及無內波或弱內波影響 (2站)，其中後兩區物理環境條件相似，被歸類為控制組，其餘為內波影響組。結果發現Synechococcus 與 Picoeukaryotes在內波影響組其深度積分平均值的總平均值(19.92 ×103 及 3.76 ×103 cells ml-1)為控制組 (4.05×103 及 1.53 ×103cells ml-1) 數量的三倍以上；而Prochlorococcus的豐度變化則是與上述兩者呈現相反的情形，在上舉型內波影響區數量減少 (28.68 ×103cells ml-1)，於控制組有較高的數量分布 (52.17 ×103cells ml-1) 。上述結果和前人的觀點相似，在光照與溫度條件充足時，Synechococcus於富營養鹽區有較多的數量， Prochlorococcus則在營養鹽低的環境數量較多，Picoeukaryotes生物量之空間變動與Synechococcus類似，但Picoeukaryotes組成複雜，何種生態因子影響其生物變動尚未解明。空間分布上，自營性生物主要分布於躍層之上 (溫度高於20。C)， Synechococcus棲息偏向表層， Prochlorococcus主要棲息於次表層，推測可能與光強度抵禦機制有關。整體而言，在內波影響組受到上舉型內波帶來富營養鹽海水的影響，使得偏好高營養鹽的Synechococcus 與Picoeukaryotes有較高的數量分佈，為東沙環礁附近的主要優勢物種。本篇研究結果顯示東沙環礁受南海內波的影響，超微浮游生物的組成與南中國海時間序列站 (SEATS站) 呈現完全不同的情形，說明內波活動對於東沙環礁生態系有著相當重要的影響力。

The South China Sea (SCS) is famous for its internal waves (IWs). To explore its impacts on the diel distribution patterns of picophytoplankton, including Synechococcus , Prochlorococcus and Picoeukaryotes, a total of seven anchored studies were conducted during the period of 2012~2013 in the SCS areas with different physical conditions. These are areas subjected to elevation IWs (4 sites), depression IWs (1 site) and weak or no IWs (2 sites). The latter two areas serve as the control sites. Results indicated that Synechococcus and Picoeukaryotes showed higher abundance in elevation IWs sites (19.92 ×103 and 3.76 ×103 cells ml-1, respectively) than in depression and no IWs sites (4.05 ×103 and 1.53 ×103 cells ml-1, respectively). The depth-integrated averaged abundance values of Synechococcus and Picoeukaryotes increased 5- and 2.5-fold higher than control sites, respectively. Prochlorococcus showed a contrast pattern with much lower abundance in the elevation IWs sites. Our moored buoy data indicated that the IWs occurred mostly during the flood-tide period. Synechococcus and Picoeukaryotes abundance showed similar pattern with the tide cycle, suggesting that the limiting inorganic nutrients brought up to the upper-water column by the elevation IWs might have stimulated the growth of Synechococcus and Picoeukaryotes.