Peat bog pools around Tamsweg (Lungau, Austria) are typical habitats of the unicellular green alga Micrasterias denticulata. By measurement of water temperature and irradiation throughout a 1-year period (2018/2019), it was intended to assess the natural environmental strain in winter. Freezing resistance of Micrasterias cells and their ability to frost harden and become tolerant to ice encasement were determined after natural hardening and exposure to a cold acclimation treatment that simulated the natural temperature decrease in autumn. Transmission electron microscopy (TEM) was performed in laboratory-cultivated cells, after artificial cold acclimation treatment and in cells collected from field. Throughout winter, the peat bog pools inhabited by Micrasterias remained unfrozen. Despite air temperature minima down to −17.3 °C, the water temperature was mostly close to +0.8 °C. The alga was unable to frost harden, and upon ice encasement, the cells showed successive frost damage. Despite an unchanged freezing stress tolerance, significant ultrastructural changes were observed in field-sampled cells and in response to the artificial cold acclimation treatment: organelles such as the endoplasmic reticulum and thylakoids of the chloroplast showed distinct membrane bloating. Still, in the field samples, the Golgi apparatus appeared in an impeccable condition, and multivesicular bodies were less frequently observed suggesting a lower overall stress strain. The observed ultrastructural changes in winter and after cold acclimation are interpreted as cytological adjustments to winter or a resting state but are not related to frost hardening as Micrasterias cells were unable to improve their freezing stress tolerance.

Tamsweg（奥地利隆高）周围的泥炭沼泽池是单细胞绿藻Micrasterias denticulata的典型栖息地。通过测量 1 年期间（2018/2019）的水温和辐照，旨在评估冬季的自然环境压力。在自然硬化和暴露于模拟秋季自然温度下降的冷驯化处理后，确定了Micrasterias细胞的抗冻性及其霜冻硬化和耐受冰包裹的能力。在实验室培养的细胞、人工冷驯化处理后和从田间收集的细胞中进行透射电子显微镜 (TEM)。整个冬天，米克拉斯特里亚斯居住的泥炭沼泽池保持解冻状态。尽管气温最低降至-17.3°C，但水温大多接近+0.8°C。藻类无法结霜，并且在冰包裹后，细胞显示出连续的霜冻损伤。尽管冷冻胁迫耐受性没有改变，但在现场采样的细胞中观察到显着的超微结构变化，并且响应人工冷驯化处理：叶绿体的内质网和类囊体等细胞器表现出明显的膜膨胀。尽管如此，在现场样品中，高尔基体仍处于无可挑剔的状态，并且较少观察到多泡体，这表明总体应力应变较低。Micrasterias细胞无法提高其对冷冻胁迫的耐受性。