Batrachospermum turfosum Bory is one of the generalists among the few red algae that have adapted to freshwater habitats, occurring in a variety of primarily shaded, nutrient-poor micro-habitats with lotic (running) or lentic (standing) waters. Seasonal variations in water level and canopy cover can expose this sessile alga to widely fluctuating temperatures, solar irradiation and nutrient availability. Here we report on the ecophysiology of B. turfosum collected from an ultra-oligotrophic bog pool in the Austrian Alps. Photosynthesis as a function of photon fluence density (PFD) and temperature was studied by measuring oxygen evolution in combination with chlorophyll fluorescence. In addition, the effects of ultraviolet radiation (UVR) on photosynthetic pigments were analysed using HPLC and spectrophotometric methods, and cellular ultrastructure was studied using transmission electron microscopy. We found that B. turfosum is adapted to low light, with a light compensation point (Ic) and a light saturation point (Ik) of 8.4 and 29.7 μmol photons m- 2 s-1, respectively, but also tolerates higher PFDs of ~1000 μmol photons m-2 s-1, and is capable of net photosynthesis at temperatures between 5°C and 35°C. Exposure to either UV-A or UV-AB for 102 h led to a strong transient drop in effective quantum yield (ΔF/FM'), followed by an acclimation to about 70% of initial ΔF/FM' values. Ultrastructural changes included the accumulation of plastoglobules and dilated membranes after UVR treatment. Although all photosynthetic pigments strongly decreased upon UVR exposure and no UV-photoprotectants (e.g. mycosporine-like amino acids) could be detected, the alga was capable of recovering ΔF/FM' and phycobiliproteins after UVR treatment. In summary, B. turfosum tolerates a wide range of irradiation and temperature regimes, and these traits may be the basis for its successful adaptation to challenging environments.

中文翻译：

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淡水红藻 Batrachospermum turfosum (Florideophyceae) 可以适应各种光照和温度条件。

Batrachospermum turfosum Bory 是少数适应淡水栖息地的红藻中的通才之一，出现在各种主要遮蔽、营养贫乏的微栖息地，具有流动（流动）或静止（静止）水域。水位和树冠覆盖的季节性变化会使这种固着藻类暴露在广泛波动的温度、太阳辐射和养分供应中。在这里，我们报告了从奥地利阿尔卑斯山的一个超贫营养沼泽池中收集的 B. turfosum 的生态生理学。通过结合叶绿素荧光测量氧气释放来研究作为光子注量密度 (PFD) 和温度函数的光合作用。此外，使用 HPLC 和分光光度法分析了紫外线辐射 (UVR) 对光合色素的影响，使用透射电子显微镜研究细胞超微结构。我们发现 B. turfosum 适应弱光，光补偿点 (Ic) 和光饱和点 (Ik) 分别为 8.4 和 29.7 μmol 光子 m-2 s-1，但也耐受更高的 PFDs ~ 1000 μmol 光子 m-2 s-1，能够在 5°C 至 35°C 的温度下进行净光合作用。暴露于 UV-A 或 UV-AB 102 小时导致有效量子产率 (ΔF/FM') 的强烈瞬时下降，随后适应初始 ΔF/FM' 值的约 70%。超微结构变化包括 UVR 处理后塑性球和扩张膜的积累。尽管所有的光合色素在 UVR 暴露后都强烈减少，并且没有检测到 UV 光保护剂（例如类真菌孢子素氨基酸），这种藻类在 UVR 处理后能够恢复 ΔF/FM' 和藻胆蛋白。总之，B. turfosum 耐受广泛的辐照和温度条件，这些特征可能是其成功适应具有挑战性的环境的基础。