The ecological importance of algal dominated, phototrophic biofilms growing on soil surfaces

The ecological importance of algal dominated, phototrophic biofilms growing on soil surfaces

Dr. J. Jahnke

Biofilms are thin (µm to mm) layers on solid surfaces. These layers build up by microorganisms (mainly bacteria, fungi and sometimes algae), their extracellular polymeric substances (EPS), and glued anorganic and organic particles (e. g. mineral sediment and detritus).

Bare soil surfaces with only scarce vegetation, immature soil, agricultural soil between seed rows, ploughed fields, soils of arid areas, and even desert soils sometimes show, a few days after wetting, developments of greenish biofilms formed mainly by algae, so called phototrophic biofilms. Soil surface particles are glued by EPS, hyphae and trichoms forming a microhabitat which is characterized by high microbial activities.

Biofilms are beneficial to soil fertility and structure. They reduce erosion and may serve as temporary storages for nutrients. In the case of immature or desert soils, algae are sometimes the only primary producers, source for organic carbon on the one hand and for organic bound nitrogen – if dinitrogen fixing cyanobacteria are present – on the other hand.

As a part of the soil ecosystem the soil surface acts as a “hot spot” of both microbial activity and probably diversity. Nevertheless the importance of soil biofilms and soil algae for the soil ecosystem is not well understood.

We are interested in the succession and dynamic of microbial communities of soil surfaces, their dependence on abiotic and biotic environmental factors. We collect data qualitatively and quantitatively on the biotic structures e. g. particularly in restored arable soils of a lignite mining area. The results of our basic research may be a contribution to the development of monitoring systems, soil protection and utilization, biodiversity and utilization of species for biotechnical applications.

Actual fields of research:

Related Publications:

Jahnke, J., D.M. Mahlmann, P. Jacobs, U.B. Priefer (2011): The influence of growth conditions on the cell dry weight per unit biovolume of Klebsormidium flaccidum (Charophyta), a typical ubiquitous soil alga. Journal of Applied Phycology 23, 655-664

Jahnke, J., D.M. Mahlmann (2010): Differences in the cellular dry weight per unit biovolume of Phormidium autumnale (Cyanobacteria) dependent on growth conditions. Journal of Applied Phycology 22, 117-122

Mahlmann, D.M., J. Jahnke, P. Loosen (2008): Rapid determination of the dry weight of single, living cyanobacterial cells using the Mach-Zehnder double-beam interference microscope. European Journal of Phycology 43, 355-364.

Jahnke, J., T. Wehren, U.B. Priefer (2007): In vitro studies on the impact of the naked soil amoeba Thecamoeba similis Greef, feeding on phototrophic soil biofilms. European Journal of  Soil Biology 43, 14-22.

Jahnke, J. (2005): Nackte Amöben als Weidegänger auf Bodenalgenbiofilmen.

Mikrokosmos 94, 37-44.

Jahnke, J. (2004): Beobachtungen an terrestrischen Algenbiofilmen mit dem Hell- und

Dunkelfeld-Auflichtmikroskop. Mikrokosmos 93, 287-294.

Jahnke, J., U.B. Priefer (2002): Phototrophic biofilms of restored fields in the rhenish lignite

mining area: development of soil algal, bacterial, and fungal biomasses. Soil Biology and Biochemistry 34, 1157-1165.

Jahnke, J. (2001): Algenbiofilme auf Bodenoberflächen: Strukturanalyse an Paraffinschnitten.

Mikrokosmos 90, 149-156.