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Sea ice algae community
Ice algae are any of the various types of algal communities found in annual and multi-year sea or terrestrial ice. On sea ice in the polar oceans, ice algae communities play an important role in primary production. The timing of blooms of the algae is especially important for supporting higher trophic levels at times of the year when light is low and ice cover still exists. Sea ice algal communities are mostly concentrated in the bottom layer of the ice, but can also occur in brine channels within the ice, in melt ponds, and on the surface.
Because terrestrial ice algae occur in freshwater systems, the species composition differs greatly from that of sea ice algae. These communities are significant in that they often change the color of glaciers and ice sheets, impacting the reflectivity of the ice itself.
Ice-Albedo Feedback Loop (SAF)
As the ice/snow begins to melt the area the ice covers decreases which means a higher portion of land is exposed. The land underneath the ice has a higher rate of solar absorption due to it being less reflective and darker. Melting snow also has lower albedo than dry snow or ice because of its optical properties[1], so as snow begins to melt the albedo decreases, which results in more snow melting, and the loop continues. This feedback loop is referred to as the Ice–albedo feedback loop.This can have drastic effects on the amount of snow melting each season. Algae plays a role in this feedback loop by decreasing the level of albedo of the snow/ice, however the exact effect algae is having is unclear.
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Terrestrial ice algae[edit | edit source]
Algae also occur on terrestrial ice sheets and glaciers. The species found in these habitats are distinct from those associated with sea ice because the system is freshwater. Even within these habitats, there is a wide diversity of habitat types and algal assemblages. For example, cryosestic communities are specifically found on the surface of glaciers where the snow periodically melts during the day. Research has been done on glaciers and ice sheets across the world and several species have been identified. However, although there seems to be a wide array of species they have not been found is equal amounts. The most abundant species identified on different glaciers are Ancyonema nordenskioldii and Chlamydomonas nivalis .
Table 1. Algae Species Composition Across Studies on Glaciers and Ice Sheets
Genus | Species | Source |
Mesotaenium | bregrenii | |
Ancylonema | nordenskioldii | |
Cylindrocystis | brebissonii | |
Chlamydomonas | nivalis | |
Phromidemis | priestleyi | |
Oscillatoriaceae | cyanobacterium | |
Chlorooceae | cyanobacterium | |
Chroococcaceae | cyanobacterium | |
Chloroplastida | ||
Chloromonas | polyptera | |
Chlamydomonas | alpina | |
Chlamydomonas | tughillensis |
Implications for climate change[edit]
The rate of glacier melt depends on the surface albedo. Recent research has shown the growth of algae darkens local surface conditions, decreasing the albedo and thus increases the melt rate on these surfaces. Melting glaciers and ice sheets have been directly linked to increase in sea level rise. The second largest ice sheet is the Greenland Ice Sheet which has been retreating at alarming rates. Sea level rise will lead to an increase in both frequency and intensity of storm events.
On enduring ice sheets and snow pack, terrestrial ice algae often color the ice due to accessory pigments, popularly known as "watermelon snow". The dark pigments within the structure of algae increases sunlight absorption, leading to an increase in the melting rate. Algae blooms have been shown to appear on glaciers and ice sheets once the snow had begun to melt, which occurs when the air temperature is above the freezing point for a few days. The abundance of algae changes with the seasons and also spatially on glaciers. Their abundance is highest during the melting season of glaciers which occurs in the summer months. Climate change is affecting both the start of the melting season and also the length of this period, which will lead to an increase in the amount of algae growth.
This growth of algae has been studied but it is not exact effects of its influence on decreasing albedo is still unknown. Glacier algae needs to be incorporated into the snow-albedo feedback loop. The Black and Bloom project is conducting research to determine the amount algae are contributing to the darkening of the Greenland Ice Sheet, as well as algae's impact on the melting rates of the ice sheets. It is important to understand the extent to which algae is changing the albedo on glaciers and ice sheets and then should be incorporated in global climate models and used to predict sea level rise.
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- ^ Qu, Xin; Hall, Alex (2007-08-01). "What Controls the Strength of Snow-Albedo Feedback?". Journal of Climate. 20 (15): 3971–3981. doi:10.1175/JCLI4186.1. ISSN 0894-8755.