Ice algae 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. Microbial life in sea ice is extremely diverse, and includes abundant algae, bacteria and protozoa. Algae in particular dominate the sympagic environment, with estimates of more than 1000 unicellular eukaryotes found to associate with sea ice in the Arctic. Species composition and diversity vary based on location, ice type, and irradiance. In general, pennate diatoms such as "Nitschia frigida"
Gasteroid fungi described by Linnaeus in his original "Species Plantarum" of 1753, but the first critical treatment of the group was by Christiaan Hendrik Persoon in his "Synopsis methodica fungorum" of 1801. Until 1981, this book was the starting point for the naming of Gasteromycetes under the "International Code of Nomenclature for algae, fungi, and plants". Although the starting point was subsequently put back to 1753, names of gasteroid fungi used in Persoon's book are still sanctioned and cannot be replaced by earlier names. Elias Magnus Fries introduced the name Gasteromycetes for a class of fungi in his "Systema Mycologicum" of 1821,