浮游生物於微流元件中對點狀營養鹽擴散源的趨向遷移行為之討論

Abstract

本研究利用微流元件提供浮游生物點狀營養鹽濃度，觀察經6小時以上之飢餓或無飢餓狀態的浮游生物K. veneficum (CCMP426) 在不同營養鹽濃度環境下的趨化性遷移行為。微流元件結構包含了T型流道與營養鹽供給流道，我們利用改變供給營養鹽的體積流率及其濃度，在T型流道內產生不同濃度分布，將飢餓或無飢餓狀態下的浮游生物置入 1倍或0倍濃度(海水)的培養液中，觀察其趨化性隨時間的演變。 實驗結果顯示，在T型流道置入處於0倍濃度培養液中飢餓狀態下的浮游生物，而營養鹽供給流道通入1X之營養鹽的條件下，浮游生物在高濃度與高濃度梯度區域集中，代表浮游生物因飢餓會往1倍濃度之營養鹽源移動，但在浮游生物的活動力表現在速度上面並無太大差異，表示浮游生物提供營養鹽並不會影響浮游生物活動表現。然而不論在整體或局部遷移行為中，在以 =10 l min-1通入5X或10X的高濃度的營養鹽時，浮游生物皆有遠離營養鹽源的趨勢，代表浮游生物會因較高的濃度使細胞內外的滲透壓差改變過大而遠離營養鹽源。當體積流率增加時，由於對T型流道的擾動與空間上整體濃度的提高，使浮游生物族群密度有顯著的影響。當無飢餓狀態的浮游生物處在原始培養液(1X)中，對外界環境改變有較高的敏感度，在不同局部濃度或濃度梯度之族群密度的變化較明顯，族群密度隨不同的營養鹽濃度改變之差異也較大。本研究所得之結果將有助於釐清浮游生物主動游泳行為與環境濃度梯度場之關係。

In this work, we used a microfluidic device to produce various nutrient field from a point source for comparisum, and study the chemotactic behavior of K. veneficum (CCMP426). Planktonic cells are introduced after starving for 6 hours and placed in the culture medium or seawater.The microfluidic device comprised a T channel and a nutrient channel. Nutrient is injected with different volumetric flow rate and concentration so that the distribution of nutrient in the T channel is varied. The results show that higher density of starving K. Veneficum can be found in the regions of high nutrient concentration and concentration gradient when they are originally introduced in seawater with supplied to the nutrient channel.When the source of nutrient increases to 5X or 10X and is delivered at higher flow rate, planktonic cells start to exhibit negative chemotaxis, beacuase the difference osmotic pressure between inner and outer cell. The results show that starving planktonic cells seek for high concentration of nutrient up to a certain level, but tend to avoid regions with extra-high concentration. The increased volumetric flow rate will effect on the density of the planktonic cells significantly, due to the disturbance of the T channel and the increased concentration in overall space. When the plankton cells without starvation in the original culture medium (1X), it has higher sensitivity to react environment changing, and the difference of planktonic density at different local concentrations or concentration gradients is more obvious. The density of planknic cells also varies with different concentration of nutrients obviously.