Stretching and bending vibrations of water molecules absorb photons of specific wavelengths, a phenomenon that constrains light energy available for aquatic photosynthesis. Previous work suggested that these absorption properties of water create a series of spectral niches but the theory was still too simplified to enable prediction of the spectral niches in real aquatic ecosystems. Here, we show with a state-of-the-art radiative transfer model that the vibrational modes of the water molecule delineate five spectral niches, in the violet, blue, green, orange and red parts of the spectrum. These five niches are effectively captured by chlorophylls and phycobilin pigments of cyanobacteria and their eukaryotic descendants. Global distributions of the spectral niches are predicted by satellite remote sensing and validated with observed large-scale distribution patterns of cyanobacterial pigment types. Our findings provide an elegant explanation for the biogeographical distributions of photosynthetic pigments across the lakes and oceans of our planet.

水分子的拉伸和弯曲振动会吸收特定波长的光子，这种现象会限制可用于水生光合作用的光能。以前的工作表明，水的这些吸收特性会产生一系列光谱生态位，但该理论仍然过于简化，无法预测真实水生生态系统中的光谱生态位。在这里，我们用最先进的辐射传递模型展示了水分子的振动模式在光谱的紫色、蓝色、绿色、橙色和红色部分描绘了五个光谱壁龛。这五个生态位被蓝藻及其真核后代的叶绿素和藻胆素色素有效捕获。光谱生态位的全球分布通过卫星遥感进行预测，并通过观察到的蓝藻色素类型的大规模分布模式进行验证。我们的发现为光合色素在我们星球的湖泊和海洋中的生物地理分布提供了一个优雅的解释。