page_title: Ice algae
section_title: Chlamydomonas nivalis
hierarchical_section_title: Ice algae / Chlamydomonas nivalis
caption_attribution_description: right pic
context_page_description: Ice algae and snow algae are algae and cyanobacteria which grow on long-lasting snow and ice fields like glaciers. When liquid water is available between the snow and ice crystals, they may color the surface green, yellow or red during the summer months. The red pigment of some species is an intracellular protection against excessive visual light and ultraviolet radiation of the sun, which otherwise can cause photoinhibition of photosynthesis or mutations. Without it, the algae at the surface would suffer chromosome breaks and DNA mutations.
  There are also ice algal communities on sea ice. These algae are important in polar ecosystems because they provide food for krill. Krill scrape off the algae from the underside of the ice, which is colored brown by the algae. The algae may be found between ice crystals or attached to them, in the water or saltwater channels between ice crystals.
context_section_description: Chlamydomonas nivalis is a green microalga which causes, besides other closely relative species, Watermelon snow.
  Watermelon snow is snow that is reddish or pink in color, and that can have a smell similar to a fresh watermelon. This type of snow is common during the summer in alpine and coastal polar regions, such as the Sierra Nevada of California. Here, at altitudes of 10,000 to 12,000 feet (3,000–3,600 m), the temperature is cold throughout the year, and so the snow lingers from winter storms. When someone steps on the snow with algae, the footprints look red.
  Chlamydomonas nivalis is a green alga which owes its red color to a bright red carotenoid pigment (Astaxanthin). This protects the chloroplast and cell nucleus from strong visible and ultraviolet radiation. The green and red pigments absorb light and heat, which gives the alga liquid water as the snow melts around it. Algal blooms may go 25 cm (10 inches) deep. Since each cell measures 20 to 30 micrometers in diameter, a teaspoon of melted snow contains a million or more cells. The algae build up in 'sun cups', which are shallow depressions in the snow. The carotenoid pigment absorbs heat, which deepens the sun cups, and makes the glaciers and snowbanks melt faster.
  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.
  Some specialised species feed on C. nivalis, including protozoans such as ciliates, rotifers, nematodes, ice worms and springtails.
caption: Watermelon snow streaks.
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