It’s the Fourth day of our Microbial Advent Calendar! Today we have a look at the incredible diversity in the ecosystem of Santa’s snowy surroundings. At first glance, ice sheets and glaciers are quite devoid of life, but they are in fact unique biomes. If you look closely those nutrient limited environments actually host surprisingly rich microbial communities.
A good recent review by Alexandre Anesio (here, check it out, it’s a good read) describes what is know about how those communitites settle, by taking the example of Cryoconite holes. Cryoconite is powdery windblown dust made of a combination of small rock particles, soot and microbes that is deposited and builds up on snow, glaciers, or ice caps. By reducing albedo and increasing localised melting this forms water-filled holes in ice surfaces. These sediments then submerged in unfrozen water become oases of life.
Filamentous Cyanobacteria are the early colonizers of those pockmarks and produce extracellular polysaccharide filaments to protect themselves against cold and UV and/or scavenge for nutrients. Although present in low abundance, the Cyanobacteria will be the base of a food web, which is able to sustain a rich heterotrophic microbial population. The microbial population will be able to feed on the carbon of the extracellular polysaccharide and will eventually build up to mature biofilms. To add to the communities interactions, the whole community will be then eventually top-down controlled by viruses.