Poirier Mackenzie C, Fugard Kassandra, Cvetkovska Marina
Department of Biology, University of Ottawa, 30 Marie-Curie Pr., Ottawa, ON, K1N 6N5, Canada.
Photosynth Res. 2025 Jan 20;163(1):9. doi: 10.1007/s11120-024-01127-0.
The perennially ice-covered Lake Bonney in Antarctica has been deemed a natural laboratory for studying life at the extreme. Photosynthetic algae dominate the lake food webs and are adapted to a multitude of extreme conditions including perpetual shading even at the height of the austral summer. Here we examine how the unique light environment in Lake Bonney influences the physiology of two Chlamydomonas species. Chlamydomonas priscui is found exclusively in the deep photic zone where it receives very low light levels biased in the blue part of the spectrum (400-500 nm). In contrast, Chlamydomonas sp. ICE-MDV is represented at various depths within the water column (including the bright surface waters), and it receives a broad range of light levels and spectral wavelengths. The psychrophilic character of both species makes them an ideal system to study the effects of light quality and quantity on chlorophyll biosynthesis and photosynthetic performance in extreme conditions. We show that the shade-adapted C. priscui exhibits a decreased ability to accumulate chlorophyll and severe photoinhibition when grown under red light compared to blue light. These effects are particularly pronounced under red light of higher intensity, suggesting a loss of capability to acclimate to varied light conditions. In contrast, ICE-MDV has retained the ability to synthesize chlorophyll and maintain photosynthetic efficiency under a broader range of light conditions. Our findings provide insights into the mechanisms of photosynthesis under extreme conditions and have implications on algal survival in changing conditions of Antarctic ice-covered lakes.
南极洲常年被冰雪覆盖的邦尼湖被视为研究极端环境下生命的天然实验室。光合藻类在该湖的食物网中占主导地位，并适应了多种极端条件，包括即使在南半球夏季最盛时也常年处于阴影之中。在此，我们研究邦尼湖独特的光照环境如何影响两种衣藻属物种的生理特性。普氏衣藻仅发现于深光合带，在那里它接收到的光照水平极低，且光谱偏向蓝光部分（400 - 500纳米）。相比之下，ICE - MDV衣藻在水柱的不同深度（包括明亮的表层水域）都有分布，它接收到的光照水平和光谱波长范围更广。这两个物种的嗜冷特性使其成为研究极端条件下光质和光量对叶绿素生物合成及光合性能影响的理想系统。我们发现，与蓝光相比，适应阴影环境的普氏衣藻在红光下生长时积累叶绿素的能力下降，且出现严重的光抑制现象。这些影响在较高强度的红光下尤为明显，表明其适应不同光照条件的能力丧失。相比之下，ICE - MDV衣藻在更广泛的光照条件下仍保留了合成叶绿素和维持光合效率的能力。我们的研究结果为极端条件下的光合作用机制提供了见解，并对南极冰雪覆盖湖泊环境变化中藻类的生存具有启示意义。
