English: Measuring cryoconites on Longyearbreen glacier during field work of Arctic microbiology course, Svalbard.Although glaciers are considered free of living organisms, there are areas like supraglacial water-filled depressions called cryoconite holes. They can be 0,5 cm to a metre in diameter and up to 0,5 m deep and formed when dark granular matter is deposited onto the surface of the glacier and the low albedo of the matter causes increased absorption of solar energy, which results in melting of the ice and subsequently formation of a water-filled hole with dark granular material at the base. They are considered as microbial hotspots, where carbon and nutrients help the growth of photosynthetic and heterotrophic microorganisms