Chlamydomonas nivalis, commonly known as snow algae, also referred to as Chloromonas typhlos, is a unicellular red-coloured photosynthetic green alga. It is found in the snowfields of the alps and polar regions all over the world and on all seven continents.Hoham, Ronald W.; Remias, Daniel (2020-04). "Snow and Glacial Algae: A Review1". Journal of Phycology. 56 (2): 264–282. doi:10.1111/jpy.12952. ISSN 1529-8817. PMC 7232433. PMID 31825096. There are four known genera causing red snow: Sanguina, Chlainomonas, Chlamydomonas, and Chloromonas.Matsumoto, Maya; Hanneman, Clare; Camara, A. G.; Krueger‐Hadfield, Stacy A.; Hamilton, Trinity L.; Kodner, Robin B. (2024-06). "Hypothesized life cycle of the snow algae Chlainomonas sp. (Chlamydomonadales, Chlorophyta) from the Cascade Mountains, USA". Journal of Phycology. 60 (3): 724–740. doi:10.1111/jpy.13454. ISSN 0022-3646. Chlamydomonas nivalis is one of the primary algae responsible for causing the phenomenon of watermelon snow (also blood snow, raspberry snow), where patches of snow appear red or pink. The first account of microbial communities that form red snow was made by Aristotle. Researchers have been active in studying this organism for over 100 years.
Although C. nivalis is closely related to Chlamydomonas reinhardtii, the environmental conditions each species inhabits are very different with C.nivalis inhabiting the meltwater in-between the spaces of snow and ice crystals in the snow pack.Gray, Andrew; Krolikowski, Monika; Fretwell, Peter; Convey, Peter; Peck, Lloyd S.; Mendelova, Monika; Smith, Alison G.; Davey, Matthew P. (2021-06-16). "Remote Sensing Phenology of Antarctic Green and Red Snow Algae Using WorldView Satellites". Frontiers in Plant Science. 12. doi:10.3389/fpls.2021.671981. ISSN 1664-462X. The habitat of C. nivalis subjects the cells to environmental extremes including limited nutrients, low temperatures, and intense sunlight. In comparison with the mesophilic C. reinhardtii, C. nivalis has special mechanisms that allow it to be cryotolerant and survive on rock surfaces as well as in soil, meltwater, and snow. Secondary carotenoids, a thick cell wall, and particles on the cell wall are some characteristics that protect the cyst from light, drought, and radiation stress. Although the seasonal mobile to dormant life cycle of C. nivalis is complex, it also helps the algae exploit its niche and survive unfavourable conditions. As a result, C. nivalis is one of the best known and studied snow algae. When taking account of the photoprotective effect of its secondary carotenoid, astaxanthin, among the other adaptive mechanisms to its extreme habitat, it can be understood how C. nivalis became so dominant in microbial snow algae communities. Green motile offspring are produced in the spring and throughout the summer. They develop into red dormant cysts, the stage where this organism spends most of its life cycle, as the winter season begins and remain a cyst until the spring.
This alga is an interesting organism for researchers in various fields to study due to its possible role in lowering global albedo, ability to survive in extreme environments, and production of commercially relevant compounds. Additionally, its life cycle is still being studied today in an effort to better understand this organism and amend previous classification errors.
Etymology The name Chlamydomonas nivalis is of compound Greek and Latin origin. Chlamydomonas is ultimately derived from the Ancient Greek χλαμύς (khlamús, "cloak, mantle") and μονάς (monás, "solitary"), while nivalis, from the Latin nivālis, translates to 'found growing in or near snow', as this species of algae are only found associated with snow or near snowy areas.Guiry, M. D. in Guiry, M.D. & Guiry, G.M. (2018). AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; Accessed on: 04 March 2018.
Morphology Red snow has a variety of forms with cell development stages being considered to correspond with cell form.Fiołka, Marta J.; Takeuchi, Nozomu; Sofińska-Chmiel, Weronika; Mieszawska, Sylwia; Treska, Izabela (2020-11-05). "Morphological and physicochemical diversity of snow algae from Alaska". Scientific Reports. 10 (1): 19167. doi:10.1038/s41598-020-76215-x. ISSN 2045-2322. Cell wall structure is typically what differentiate cell types, with smooth, nippled, papillae, and wrinkled being among the most common. Ribbed, rosette, ellipsoid, and star formations have also been observed.Remias, Daniel; Karsten, Ulf; Lütz, Cornelius; Leya, Thomas (2010-03-14). "Physiological and morphological processes in the Alpine snow alga Chloromonas nivalis (Chlorophyceae) during cyst formation". Protoplasma. 243 (1–4): 73–86. doi:10.1007/s00709-010-0123-y. ISSN 0033-183X. Cell sizes vary with red spheres being 35.96 ± 4.9 μm in diameter, ellipsoid/oval shaped cells being 20–28 mm long and 11–15 mm wide, and star shaped cells being 40–50 μm.Almela, Pablo; Elser, James J.; Zmuda, Anthony; Niehaus, Thomas; Hamilton, Trinity L. (2026-02). "Community‐driven variations in snow algae color modulate snow albedo reduction". New Phytologist. 249 (4): 1739–1752. doi:10.1111/nph.70775. ISSN 0028-646X. PMC 12825401. PMID 41292094.Muramoto, K., Kato, S., Shitara, T., Hara, Y., & Nozaki, H. (2008). Morphological and Genetic Variation in the Cosmopolitan Snow Alga Chloromonas nivalis (Volvocales, Chlorophyta) from Japanese Mountainous Area. Cytologia, 73, 91-96.Kawecka, B. (1981). Biology and ecology of snow algae. Acta Hydrobiol, 23, 211-215. Chlamydomonas nivalis have been observed to have primary and secondary cell walls, where the primary will be shed leaving a smooth cell wall behind.Remias, Daniel; Karsten, Ulf; Lütz, Cornelius; Leya, Thomas (2010-07). "Physiological and morphological processes in the Alpine snow alga Chloromonas nivalis (Chlorophyceae) during cyst formation". Protoplasma. 243 (1–4): 73–86. doi:10.1007/s00709-010-0123-y. ISSN 0033-183X. Secondary cell walls tend to constitute to more mature cysts of Chlamydomonas nivalis and being ribbed where as younger cysts were associated with being rounder, lobed, and smooth-walled.Remias, D., Lütz-Meindl, U., & Lütz, C. (2005). Photosynthesis, pigments and ultrastructure of the alpine snow alga Chlamydomonas nivalis . European Journal of Phycology, 40(3), 259–268. https://doi.org/10.1080/09670260500202148 Furthermore, cell walls can be found to be 66 to 154 nm thick for smooth cell walled cysts.Ezzedine, Jade A.; Uwizeye, Clarisse; Si Larbi, Grégory; Villain, Gaelle; Louwagie, Mathilde; Schilling, Marion; Hagenmuller, Pascal; Gallet, Benoît; Stewart, Adeline; Petroutsos, Dimitris; Devime, Fabienne; Salze, Pascal; Liger, Lucie; Jouhet, Juliette; Dumont, Marie (2023-11-18). "Adaptive traits of cysts of the snow alga Sanguina nivaloides unveiled by 3D subcellular imaging". Nature Communications. 14 (1): 7500. doi:10.1038/s41467-023-43030-7. ISSN 2041-1723.
Dispersal While snow algae are considered to be a cosmopolitan species and Chlamydomonas nivalis has been observed across bipolar regions, the mechanisms behind their dispersal and migrations are not clear. Additional research across latitude-ranges of red snow patches on glacial and snow fields will be advantageous in understanding the colonizing habits of snow algae.
Description The seasonal life cycle of C. nivalis can be broken down to three stages based on the color of the cell as a result of carotenoid composition, which are green, orange, and red.Lütz, C. (2012). "Plants in Alpine Regions". Springer-Verlag Wien. doi: 10.1007/978-3-7091-0136-0 Orange cells and red cells are the most difficult to differentiate as they look similar while the red and green cells are easiest to differentiate as they have more significant differences in composition.Beer, T.; Tanaka, Z.; Netzter, N.; Rothschild, L. J.; Chen, B. (2011). "An analysis of uncultured extremophilic snow algae by non-invasive single cell Raman spectroscopy". Proc. SPIE 8152, Instruments, Methods, and Missions for Astrobiology XIV, 81520F. doi: 10.1117/12.896481 Cells at the red stage were previously described as a separate species than the green cells, but were later discovered to be different stages of the C. nivalis''' complex life cycle.Cvetkovska, M. C.; Hüner, N. P. A.; Smith, D. R. (2016). "Chilling out: the evolution and diversification of psychrophilic algae with a focus on Chlamydomonas". Polar Biol. 40 (6): 1169-1184. doi: 10.1007/s00300-016-2045-4
Small green coloured motile cells of the young C. nivalis at the green stage are produced in spring or early summer when temperatures are warmer and zygotes undergo meiosis in meltwater pools.Bidigare, R. R.; Ondrusek, M. E.; Kennicutt II, M. C.; Iturriaga, R.; Harvey, H. R.; Hoham, H. W.; Macko, S. A. (1993). "Evidence for a photoprotective function for secondary carotenoids of snow algae". J. Phycol. 29 (4): 427-434. The biflagellated cells are slightly oval and about 5-15 μm in diameter.Stibal, M.; Elster, J.; Sabacka, M.; Kastovska, K. (2007). "Seasonal and diel changes in photosynthetic activity of the snow alga Chlamydomonas nivalis (Chlorophyceae) from Svalbard determined by pulse amplitude modulation fluorometry". FEMS Microbiology Ecology. 59 (2): 265–273. doi: 10.1111/j.1574-6941.2006.00264.x. In this asexually reproductive phase, the cells are sensitive to temperature and drought stress. They avoid unfavorable light and temperature by swimming in the snow until they reach more optimal conditions.Remias, D.; Lütz-Meindl, U.; Lütz C. (2005). "Photosynthesis pigments and ultrastructure of the alpine snow alga Clamydomonas nivalis". European Journal of Phycology. 40 (3): 259-268, doi: 10.1080/09670260500202148 Chloroplasts of green cells are irregularly shaped. The dominating pigment, chlorophyll, gives the cell its characteristic hue and facilitates maximum cell growth through light absorption. Secondary carotenoid concentrations are much lower at this stage as the cells need photosynthetically active radiation for energy and growth. Cells in the green stage also have less organic and inorganic particles on their surface compared to mature cysts.
Later in the season, when nitrogen and nutrients becomes limited and radiation stress increases, the green cells will develop into flagellated sexual gametes that mate and produce new zygotes that have lost their flagella and are capable of surviving the winter period. Transformation into the zygote, or hypnoblast, is characterized by the production and accumulation of reserve materials that include sugars and lipids as well as the formation of esterified secondary carotenoids. The secondary carotenoids will turn the green zygotes orange as they accumulate in the area around the plastids of the cell to protect the zygotes from UV radiation. Orange and red spores can be seen throughout the summer. During this stage, the cell wall will also begin to thicken to help the cell tolerate freezing temperatures and UV light. In addition, the color of these pigments reduces albedo such that individual cells may melt nearby ice and snow crystals to access limiting nutrients and water in an otherwise unavailable frozen state.Dial, R.; Ganey, G.; Skiles, M. (2018). "What color should glacier algae be? An ecological role for red carbon in the cryosphere". FEMS Microbiology Ecology. 94 (3): fiy007. https://academic.oup.com/femsec/article/94/3/fiy007/4810544; Accessed on: 18 December 2018
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