Red snow caused by spherical cysts can be found worldwide, while an orange snow phenomenon caused by spherical cells is restricted to (Sub-)Arctic climates. Both bloom types, occurring in the same localities at Svalbard, were compared ecophysiologically. Using a combination of molecular markers and light- and transmission electron microscopy, cells were identified as Sanguina nivaloides and Sanguina aurantia (Chlorophyceae). In search for reasons for a cosmopolitan vs. a more restricted distribution of these microbes, significant differences in fatty acid and pigment profiles of field samples were found. S. aurantia accumulated much lower levels of polyunsaturated fatty acids (21% vs. 48% of total fatty acids) and exhibited lower astaxanthin-to-chlorophyll-a ratio (2–8 vs. 12–18). These compounds play an important role in adaptation to extreme conditions at the snow surface and within snow drifts. Accordingly, the performance of photosystem II showed that one third to nearly half of the photosynthetic active irradiation was sufficient in S. aurantia, compared to S. nivaloides, to become light saturated. Furthermore, formation of plastoglobules observed in S. nivaloides but missing in S. aurantia may contribute to photoprotection. The rapid light curves of the two species show to a certain extent the shade-adapted photosynthesis under the light conditions at Svalbard (high α-value 0.16 vs. 0.11, low saturation point Ik 59 vs. 86). These results indicate significant physiological and ultrastructural differences of the two genetically closely related cryoflora species, but the reasons why S. aurantia has not been found at conditions outside (Sub-)Arctic climate types remain unknown.

中文翻译：

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环极地橙色雪藻 Sanguina aurantia 与世界性红雪藻 Sanguina nivaloides（绿藻门）的生态生理学和超微结构特征比较

由球形囊肿引起的红色雪在世界各地都可以发现，而由球形细胞引起的橙色雪现象仅限于（亚）北极气候。对发生在斯瓦尔巴特群岛同一地点的两种水华类型进行了生态生理学比较。结合分子标记以及光学和透射电子显微镜，细胞被鉴定为 Sanguina nivaloides 和 Sanguina aurantia （绿藻纲）。在寻找这些微生物的世界性分布与更有限分布的原因时，发现了现场样品的脂肪酸和色素特征的显着差异。S. aurantia 积累的多不饱和脂肪酸水平要低得多（占总脂肪酸的 21% vs. 48%），并且虾青素与叶绿素-a 的比率较低（2-8 vs. 12-18）。这些化合物在适应雪面和雪堆内的极端条件方面发挥着重要作用。因此，光系统 II 的性能表明，与 S. nivaloides 相比，S. aurantia 三分之一到近一半的光合有效辐射足以达到光饱和。此外，在 S. nivaloides 中观察到但在 S. aurantia 中缺失的质体球的形成可能有助于光保护。两个物种的快速光变曲线在一定程度上显示了斯瓦尔巴特群岛光照条件下的荫适应光合作用（高α值0.16 vs. 0.11，低饱和点Ik 59 vs. 86）。这些结果表明，这两种遗传上密切相关的冷冻植物物种存在显着的生理和超微结构差异，但在（亚）北极气候类型以外的条件下没有发现 S. aurantia 的原因仍然未知。