藻類による彩雪現象 (雪氷の生態学 : 彩雪の生物群集)

概要

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雪が着色する現象は世界の山岳地帯や極地でしばしば観察されている. 最も普通にみられるのは赤雪でその多くはChlamydomonas のような単細胞性の緑藻が原因である. しかし本報告の尾瀬においては４月から５月かけての融雪期にみられる大規模な雪の赤褐色化は, 直径約10μm の球もしくは楕円状の赤褐色粒子によるものである. 赤褐色の原因は単細胞性の緑藻Hemitoma 胞子の被殻に多量に含まれる酸化鉄が原因である.Spring red snow phenomenon is frequently observed in alpine and polar environments with extremely low temperature, high light intensity, and low nutrient levels around the world. The red snow phenomenon is mostly caused by the green algae such as Chlamydomons and Chloromonas, and its reddish color is derived from carotenoids in the algae's vacuoles. However, we have recently found that the red snow in Oze National Park in Japan is caused by the green algae, Hemitoma, and its reddish color is caused by Fe-oxide accumulating at the surface of spores in the alga. Therefore, the cause of the red snow is divergent. In this review, we overview recent knowledge of the algae-dependent red snow.