Soil algae

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As a soil algae are eukaryotic , photoautotrophic microorganisms referred to, their habitat on the soil surface or in the interior of the soil is located. They are almost always accompanied by prokaryotic cyanobacteria that live in the same ecological niche . Terrestrial algae have to be adapted to life on land due to the at least temporarily limited water availability; the conventional habitats of algae, on the other hand, are all types of water.

The Danish botanist Johannes Boye Petersen differentiated three ecological groups according to the biotope : aero-terrestrial algae or air algae live on substrates that are permanently elevated above the soil surface (e.g. tree trunks), hydro-terrestrial algae come on permanently wet or water-saturated soils in front. The actual soil algae form the third group, which he calls eu-terrestrial algae.

Soil algae come from almost all groups of algae that live in freshwater . The main focus of the represented clans is the thread-like and coccoid " green algae " (especially Chlorophyceae ), the diatoms and the yellow-green algae (Xanthophyceae).

Since the supply of light below the soil surface decreases rapidly, a mixotrophic way of life is assumed for a number of species in order to survive in areas that are not sufficiently bright for photosynthesis . Some species use sunlight as an energy source, but are dependent on the supply of certain organic molecules. An ecologically similar habitat is inhabited by air algae, which specialize in surfaces such as boulders or tree bark. Functionally, the snow algae , whose cells survive in alpine or polar soils after melting, are located in the vicinity of soil algae .

As the primary producer, soil algae are an important part of the Edaphon . At special locations where abiotic environmental factors such as extreme temperatures, exposure or water availability prevent higher plants from growing, certain soil algae can develop biogenic soil crusts, which, accompanied by cyanobacteria, represent a climax stage (e.g. . in deserts or on heathland). They are also often significant in the formation of soil on raw soil locations, where they accumulate nutrients and improve the soil structure through biomass or crust formation and soil erosion can be slowed down.

Under favorable conditions, populations of soil algae can be seen with the naked eye as a green tinge on soil surfaces. Individually, due to their cell size, they cannot be seen with the naked eye and therefore belong to the class of microalgae. Even with the help of the light microscope, many clans cannot be addressed in more detail due to their often very reduced or similar morphological features. For a more precise investigation of the species composition, it is therefore essential to establish and observe cultures in which the isolated species are studied in their life cycle.

literature

  • Ettl, Hanuš, Gärtner, Georg: Syllabus of soil, air and lichen algae. Springer Spectrum 2014, 2nd edition.
  • Kadereit, JW, Körner, C., Kost, B., Sonnewald, U .: Strasburger - Textbook of Plant Sciences. Springer Spectrum 2014, 37th edition.
  • Blaine Metting: The Systematics and Ecology of Soil Algae. Botanical Review Vol. 47, No. 2: 195-312.