Physiological ecology of marine planktonic prochlorophytes

研究了黑潮及其邻近海域浮游原绿植物的空间分布，并测定了它们的生长对光环境的依赖性。原绿藻在黑潮及其邻近的亚热带沃茨普遍存在。它们的垂直分布表明，在水柱分层的初始阶段，次表层最大值约为表面照度的10%，夏季约为深度的1%，叶绿素a的最大值在那里发展。二乙烯基叶绿素a（chla 2）与叶绿素B的比值沿着深度增加，表明色素对低强度蓝光的适应。原绿藻是重要的初级生产者在常备库存：叶绿素a 2占荧光测定叶绿素a的平均29%。与此相反，原绿藻是在浅海和沿海浮游植物群落的次要成分，他们没有发现在Oyashio水，亚北极水域。通过比较叶绿素a 2的分布和在蓝光激发下发出红色荧光的<1 μ m颗粒物的数量丰度，发现东海陆架上存在着除原绿藻以外的许多颗粒物。培养实验表明，在14 L：10 D光周期条件下，三种菌株的最佳光通量范围为53 ~ 283 mumol·m^<-2>s^-1<-1>，最大比生长速率为0.26 ~ 0.66 d ^-1。叶绿素a 2含量和相对叶绿素B含量随生长光强的降低而增加。生长所需的最低光照强度低于4 μ mol·m ~（-1）·<-2>s ~（-1）<-1>。这些结果与实地调查结果吻合得很好。

The present study investigated spatial distribution of marine planktonic prochlorophytes in the Kuroshio and adjacent area and determined their growth dependence on light environments. Prochlorophytes occurred in Kuroshio and adjacent subtropical waters ubiquitously. They were found at temperature or 18 to 28ﾟC with maximum occurrence at 21ﾟC.their vertical distribution showed subsurface maximum around 10% illumination of the surface at the initial phase of stratification of the water column, and around 1% depth in summer, where the deep maxima of chlorophyll a developed. Ratio of divinylchlorophyll a (chl a2), a marker pigment of prochlorophytes to chlorophyll b increased along with depth indicating pigment adaptation to blue light fields of low intensity. Prochlorophytes were important primary producers in terms of standing stock : chl a2 occupied 29% of fluorometrically determined chlorophyll a on the average. In contrast, prochlorophytes were minor constituents in neritic and coastal phytoplankton communities and they were not found in Oyashio water, subarctic water. Based on comparison of distributions of chl a2 and numerical abundance of <1mum particles that emitted red fluorescence under blue light excitation, many particles other than prochlorophytes were detected on the shelf of the East China Sea. Pigment signature suggested these were likely either chlorophytes or prasinophytes.Culture experiment revealed variations in light-dependency of growth among three strains used with optimal photon flux ranging from 53 to 283mumol m^<-2>s^<-1> and maximum specific growth rates of 0.26 to 0.66 d^1 at 14L : 10D photoperiod. Cellular chl a2 content and relative chlorophyll b contents increased with decrease in growth light intensity. Minimum light intensity for their growth was below 4mumol m^<-2>s^<-1>. These findings agreed well with the results obtained in the field survey.