Zawierucha, M. Kolicka, N. Takeuchi and Ł. Kaczmarek
Glaciers support a whole range of life, from bacteria and algae to more complex organisms such as mosses, nematodes and arachnids, despite their harsh environmental conditions. Indeed, it has been suggested that glaciers should be treated as a new biome altogether. Cryoconite holes, which are small, water-filled reservoirs on the surface of glaciers, form microecosystems complete with simple trophic webs that sustain primary producers and primary and even secondary consumers. Cryoconite holes are formed when windblown dust or soot land on the surface of a glacier and start melting the ice, as they absorb heat from the sun owing to their dark colour. In their article published in the Journal of Zoology, Krzysztof Zawierucha and his co-authors provided the first comprehensive review of the fauna found living in cryoconite holes on glaciers around the globe. They found that only 26 papers published since 1885 have reported on cryoconite hole fauna, and these studies were conducted on glaciers located in the Arctic, Antarctic, Patagonia, Alps and Himalayas. These papers had found invertebrates from five phyla (Rotifera, Annelida, Tardigrada, Nematoda and Arthropoda) and 41 taxa living in cryoconite holes, forming basic food webs where primary consumers feeding on microbes and algae are prey to secondary consumers.
Moreover, some of these animals are specifically adapted to these extreme environments: they may enter anabiosis in unfavourable conditions or produce dormant eggs, or have black pigment granules in their epidermis to protect them from the high levels of UV radiation, particularly in the polar regions. Furthermore, other studies have found in cryoconite holes bacteria that produce special antifreeze proteins. Further research will probably find more taxa inhabiting cryconite holes, and improve our understanding on how organisms adapt to living in these extreme environments. However, accelerated melting of glaciers due to climate change means that these ecosystems are disappearing at increasing rates, making them one of the most endangered ecosystems in the world.