Light is a fundamental resource for phytoplankton. To utilize the available light, most phytoplankton species possess pigments in taxon-specific combinations and quantities, which in turn result in a specific use of certain wavelengths. This optimizes the light use efficiency, allows for a complementary use of light, and may be an additional driver for community structure. While the effects of light intensity on phytoplankton biomass production and community composition have been intensively studied, here we focused on the effects of specific light spectrum quality (thus light color) on a natural phytoplankton community. In a controlled mesocosm experiment we reduced the supplied wavelength range to its blue, green, or red part of the light spectrum and compared the responses of each treatment to a full spectrum control over 28 d. Highest community growth rates were observed under blue, lowest under red light. Light absorption by the communities showed adaptation toward the supplied wavelength range. Community composition was significantly affected by light quality treatments, driven by Bacillariophyta and Chlorophyta, whereas pigment composition was not. Furthermore, lower species richness but higher evenness occurred when communities were exposed to red light compared to the full spectrum. We expected the response of phytoplankton communities to changes in the light spectrum to be driven by a combination of species sorting and pigment acclimation; however, the effect of species sorting turned out to be stronger. Our study showed that, even if species might acclimate, changes in the available light spectrum affect primary production and phytoplankton community composition.

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水下光光谱质量的变化改变了浮游植物群落组成

光是浮游植物的基本资源。为了利用可用光，大多数浮游植物物种都具有特定于分类群的组合和数量的色素，这反过来又导致特定波长的特定使用。这优化了光的使用效率，允许光的互补使用，并且可能是社区结构的额外驱动力。虽然已经深入研究了光强度对浮游植物生物量产生和群落组成的影响，但在这里我们专注于特定光谱质量（即浅色）对天然浮游植物群落的影响。在受控的中胚层实验中，我们将提供的波长范围减少到光谱的蓝色、绿色或红色部分，并将每种处理的响应与 28 天的全光谱控制进行比较。在蓝色光下观察到最高的群落增长率，在红光下观察到最低。群落的光吸收显示出对提供的波长范围的适应。群落组成受光质处理的显着影响，由芽孢杆菌和叶绿藻驱动，而色素组成则没有。此外，与全光谱相比，当群落暴露于红光时，物种丰富度较低，但均匀度较高。我们预计浮游植物群落对光谱变化的反应是由物种分类和色素适应的组合驱动的；然而，物种分类的效果却更强。我们的研究表明，即使物种可能适应环境，可用光谱的变化也会影响初级生产和浮游植物群落组成。