Ice algae
During the winter months, when white snow covers them, the algae become dormant. In spring, nutrients, increased levels of light and meltwater, stimulate germination. Once they germinate, the resting cells release smaller green flagellate cells which travel towards the surface of the snow. Once the flagellated come close to the surface, they may lose their flagellae and form thick-walled resting cells, or they may function as gametes, fusing in pairs to form zygotes.