Yet surprsingly, active C. Here's what a different species of Chlamydomonas looks like swarming in water to give you the idea. Here's a closeup alongside a slinky green alga called Euglena. The homely, roundish cells are Chlamydomonas , and you can see both their paired flagella and the cells' various organelles aren't you glad our bodies aren't transparent? The cells know which way to drive in their snowbank because they can see. Most species of Chlamydomonas -- and I assume C. Versions of the same ancient chemical are found to cite but a few examples in your own eyes, in sea-faring protists called dinoflagellates, and in salt-loving photosynthetic archaea living in natron flats, who use it not to see but to make supper.
And as you saw, the vegetative cells of Chlamydomonas nivalis are green while growing. So how is it that they color snow pink? Since, like lichens, these algae must contend with intense UV bombardment, they need sunscreen to protect their light-harvesting molecule chlorophyll, and lots of it. They need it most in their resting stage -- the one that might have to survive for a long time on top of a snow drift or soil prior to next fall's snows.
That stage is the zygote. In many species of snow algae, this single-celled, immobile product of mating is packed with carotenoids click here for some nice images. Carotenoids are brightly-colored UV-absorbing pigments. This huge class of biochemicals includes beta-carotene.
When consumed and transported to your eyes, beta carotene performs a similar job for you by absorbing UV, thereby protecting your retina from diseases like macular degeneration. Like the carotenoids found in fruits and vegetables, the chemicals also lend zygotes an orange, red or rusty hue under the microscope. Midummer snow reveals its chromatic algal payload most readily on permanent snow fields in sunny, dry areas; rain tends to wash them away.
Joyce Gellhorn says these self-reinforcing pink pits are called "sun cups". Not all snow algae color snow pink. Compressing the snow intensifies the color and density of the algal cells.
Microscopic view X of the bright red resting cells aplanospores of snow algae Chlamydomonas nivalis. The larger winged structure lower left is a pollen grain from the timberline whitebark pine Pinus albicaulis. The smaller, transparent-green cells center with a lipid droplet at each end are Chloromonas , another species of snow algae.
B rian Duval and his associates Journal of Applied Phycology Volume , have shown that snow algae cells aplanospores exposed to ultaviolet light produce antioxidant compounds called flavonoids.
Flavonoids are 3-ring phenolic compounds consisting of a double ring attached by a single bond to a third ring. In leaves they block far ultraviolet UV light which is highly destructive to nucleic acids and proteins , while selectively admitting light of blue and red wavelengths which is crucial for photosynthesis. Flavonoids include water soluble pigments such as anthocyanins that are found in cell vacuoles.
The defensive value of flavonoid production in snow algae may be explained by UV-stimulated phenolic compounds in other plants, including the highly-acclaimed resveratrol. Future research on antioxidant production in snow algae may have valuable pharmacological implications in the treatment of certain cancers in humans. The pretty pigmentation isn't the only reason to pay attention to the phenomenon, though.
It's actually pretty problematic in terms of speeding up the process of melting glaciers. In a study published in June on Nature Communications , scientists say pink snow plays a "crucial role in decreasing albedo," the amount of light or radiation reflected by a surface—meaning it could result in higher melt rates. Because of this, the team concluded that the effect should be considered in climate models. No matter how cool pink snow may look, we'll stick to dreaming of the white stuff instead.
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