A field survey was carried out in early spring to investigate the growth physiology and efficiency of cyst formation of Alexandrium tamarense in low water temperatures. A bloom of A. tamarense occurred in a stratified water column, formed by river inflow. The in situ growth rate estimated from daily cell abundance was high, 0.33 divisions day(-1), at 7.5-9 degrees C. New cysts began to be observed during the late growth phase. Maximum cyst flux (600 cysts cm(-2) day(-1)) was observed just after maximum cell abundance occurred. PO(4)-P Chl a(-1) gradually decreased and reached extremely low levels beyond the mid-growth phase of A. tamarense. As sinking cysts were also recognized at that time, it suggests cyst formation may have been induced by depletion of phosphorus source. The incidence of cyst formation (C.I) was 30%. The number of C.I was the same as reported previously for batch cultures under conditions suitable for vegetative growth. These results indicate that A. tamarense grows with considerably higher growth rate and transforms to cysts in high numbers, in low water temperatures in the field.

中文翻译：

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日本东北部低水温下有毒鞭毛藻 Alexandrium tamarense 的生长和包囊形成

在早春进行了一项实地调查，以研究 Alexandrium tamarense 在低水温下的生长生理学和孢囊形成效率。A. tamarense 的大量繁殖发生在由河流流入形成的分层水体中。从每日细胞丰度估计的原位生长率很高，在 7.5-9 摄氏度时为 0.33 个师天 (-1)。在生长后期开始观察到新的包囊。就在最大细胞丰度发生后观察到最大囊肿通量（600 个囊肿 cm(-2) day(-1))。PO(4)-P Chl a(-1) 在 A. tamarense 的中期生长阶段后逐渐减少并达到极低的水平。由于当时也发现了下沉的囊肿，这表明囊肿的形成可能是由于磷源枯竭所致。囊肿形成 (CI) 的发生率为 30%。数量 C. 我与之前报道的在适合营养生长的条件下分批培养相同。这些结果表明 A. tamarense 以相当高的增长率生长，并在田间低水温下大量转化为孢囊。