Red algae on glaciers in the Arctic.

Photo Courtesy of Brocken Inaglory

Red Algae on Glaciers

By Caitlin Connelly             November 25, 2017

As the fear of climate change becomes stronger, researchers are attempting to quantify its effects on surface ice and snow in the arctic. Recently, scientists have discovered an unexpected influence on the rate of melting: Pink colored algae. This discovery has caused some concern due to its widespread geographical range in alpine and polar regions worldwide and potential impacts on the global climate systems.

The algae, scientifically named chlamydomonas nivalis and commonly referred to as “Red Algae”, are green during the winter months and lie dormant under the snow. In the spring and summer, they propel themselves up to the surface with the help of their flagellum in order to reach an environment with levels of light and water suitable for photosynthesis. At the surface, the algae produce a pink pigment called astaxanthin which masks the green pigment chlorophyll causing the algae to appear pink. During this time,  the algae covers the snow and ice sheets in layers of pink, creating the phenomenon known as “Watermelon Snow”. More importantly for the algae, the pigment astaxanthin protects its chloroplasts from the intense UV radiation present in alpine and polar environments. In addition, the pigment absorbs heat and melts surrounding snow, providing a critical water source for the algae. It is this ability of red algae to absorb heat and melt surrounding snow that scientists are interested in studying.

Albedo, a measure of how much light a surface reflects, typically depends on the color of the surface. Darker surfaces have a lower albedo, meaning that they tend to absorb more of the incoming solar energy and reflect less. The energy that is absorbed is then used to either heat or melt the surface. On the other hand, lighter surfaces, such as pure white snow, would have a high albedo since they reflect a lot if the incoming solar radiation. According to a publication in Nature Communications, the red algae phenomenon changes the albedo of surface snow and ice. Researchers from Britain and Germany examined 40 samples of ice from Greenland, Norway, Sweden, and Iceland. After comparing white snow with Red snow, the researchers determined that the albedo of the snow with the algae was reduced by 13% over the course of the summer season. Because the astaxanthin changes the color of the algae to pink, it darkens the overall color of the surface. By changing the color of the surface from a white or near white to pink, the surface albedo would decrease. The lowered albedo has the potential to increase melting of the snow and ice on the surface. Although it’s not clear how large a role the algae plays in overall melting, scientist are concerned that this “bio-albedo” effect may be a positive feedback loop that could exacerbate melting patterns and have an effect on climate systems. As the algae grows and the ice melts, it creates more water, a more hospitable environment for the algae, and then creates more algae, which causes more melting. Because climate modelers include other biological factors in their models like dust from forest fires and deserts, scientists suggest that the effect of red algae on ice and snow melting should be considered in global models.

Although algae are small, the geographic distribution of the species give it the potential for widespread effects. In addition, because temperatures in arctic and alpine ecosystems are increasing at twice the global rate, the decreased albedo caused by red algae will only further exacerbate the melting of snow and ice caused by climate change.

While it is known that the algae affect albedo, it is unclear how much the change will affect glacial and snow melting. As a result, the Black and Bloom Project (US $4 million), aims to measure how the algae will affect the melting of the Greenland ice sheet, since the sheet contains enough ice to raise sea level seven meters. In addition, the information can also be used by climate modellers to predict melting that would affect water supplies in other areas of the world as well. For example, algal blooms have been recorded on water producing glaciers in the Himalayas that support the drinking water supply, irrigation, and livelihoods of millions of people. With climate change already altering the patterns of glacial capture and release of water, understanding how algae will affect glacial melt is important for predicting water supplies for those in the surrounding area.



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Snow Alga - Chlamydomonas nivalis - Details. (n.d.). Retrieved October 19, 2017, from has increased from 10% to 17.5% since 2006.

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