Department of Biology, College of Sciences, Shantou University, Shantou 515063, Guangdong, China; STU-UNIVPM Joint Algal Research Center, College of Sciences, Shantou University, Shantou 515063, Guangdong, China.
Key Laboratory of Tropical Marine Bio-Resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510530, China.
Harmful Algae. 2019 Feb;82:26-34. doi: 10.1016/j.hal.2018.12.008. Epub 2019 Jan 4.
Light drives phytoplankton photosynthesis, so phytoplankton in their living habitats must exploit variable light levels and exposure durations, depending upon seasons, latitudes, depths and mixing events. Comparative growth, physiology and biochemical compositions were explored for the small Alexnadrium minutum (˜40 μm biovolume) and large Alexandrium catenella (˜9300 μm biovolume), globally wide spread coastal toxic red tide dinoflagellates, responding to a matrix of photoperiods (Light:Dark, 8:16, 16:8 and 24:0) and growth light irradiances. Smaller A. minutum grew faster under shorter photoperiods across growth light levels, while larger A. catenella grew fastest under longer photoperiods at the lowest applied light level. Photosystem II function responded largely to the instantaneous growth light level across photoperiod lengths, while the cell biovolume-based respiration, antioxidant capacity as well as cell composition responded more to photoperiod duration than to light level. These complex photophysiological responses resolved into linear correlations between growth rate versus cellular antioxidant activity and versus dark respiration, indicating that respiration energizes cellular antioxidant systems to benefit the growth of the cells. These results show the growth responses of Alexandrium species to light levels across photoperiods vary with species, and possibly with cell size. Together with previous results this puts a note of caution on meta-analytical extrapolations of physiological responses to light intensity derived from studies applying different photoperiods to different taxa, because different taxa show differential, even opposite growth responses to photoperiods and light intensities.
光驱动浮游植物光合作用，因此浮游植物在其生活栖息地中必须根据季节、纬度、深度和混合事件利用可变的光照水平和暴露时间。为了研究全球广泛分布的沿海有毒赤潮甲藻中的小型亚历山大藻（˜40 μm 生物量）和大型亚历山大藻（˜9300 μm 生物量），我们探索了它们的比较生长、生理和生化组成，以应对光照周期（光：暗，8:16、16:8 和 24:0）和生长光辐照度的矩阵。在整个生长光水平下，较小的 A. minutum 在较短的光照周期下生长得更快，而较大的 A. catenella 在最低应用光水平下在较长的光照周期下生长得最快。光系统 II 功能主要响应整个光照周期长度的瞬时生长光水平，而细胞生物量呼吸、抗氧化能力以及细胞组成对光照周期持续时间的响应比对光水平的响应更大。这些复杂的光生理反应在生长速率与细胞抗氧化活性之间以及与黑暗呼吸之间转化为线性相关性，表明呼吸为细胞抗氧化系统提供能量，以促进细胞的生长。这些结果表明，亚历山大藻种对光周期中光照水平的生长反应随种而异，并且可能随细胞大小而异。结合之前的结果，这就提醒人们注意，根据不同的光照周期对不同的分类群施加不同的光照强度，从生理反应推断到光强度的元分析外推可能存在问题，因为不同的分类群对光照周期和光强度表现出不同的，甚至相反的生长反应。
