Ice

Although many organisms cannot tolerate low temperatures, a few microorganisms thrive at temperatures near 0⁰C. These organisms are known as psychrophiles (cold loving). The best known of the psychrophiles are algae that are seen on the surface of snow fields in the summer months. These algae are green photosynthesizers that produce red spores. As snow melts in the summer temperatures, these red spores become visible (as shown in the picture above). The red streaks on the side of the mountain are populations of the snow alga Chlamydomonas nivalis. In the cooler months, this alga is green. When the snow starts to melt, the algae produce the distinctive red spores that become concentrated on the surface. As the spores become covered with snow again, the cells become active, and the green vegetative state of the alga is visible.