Can Microalgae Revitalize Phytotoxic Soils?

Microalgae represent a variable group of photoauto-trophic microorganisms that include both prokaryotic cyanobacteria and eukaryotic algae. Compared to higher plants, algae have faster growth, higher photo-synthetic efficiency and the ability to colonize differ-ent ecological niches. The advantage of using microal-gae for bioremediation or recultivation compared to higher plants mainly lies in their simple cell structures, easier access to CO2 and nutrients and ability to grow in extreme environments. The goal of this study was to design and apply bio-technologies for the revitalization of phytotoxic soils based on the use of cyanobacteria and microscopic algae. Microalgal strains isolated from biocrusts from the Lítov post-mining dump (Northern Czechia), or others coming from algae collections were tested in laboratory experiments for the growth on soils. Their physiological state (photosynthetic activity, cell growth and division), and growth conditions (tempera-ture, light intensity, pH, nutrition) were monitored and optimized. The lab-scale experiments were followed with selected strains (Nostoc, Desmonostoc, Trichor-mus) in greenhouse experiments on phytotoxic soils from the Lítov Dump by various ways of application. Soil analyses were conducted to evaluate the initial physical, chemical, and biological soil quality. Soil pH was lower than 3, microbial respiration and biomass were low, but not as low as could be expected for toxic substrates. Content of available nutrients, especially that of dissolved nitrogen and phosphorus, was very low. All strains tested in greenhouse experiments grew on the phytotoxic soil. The most successful was Trichormus applied with expanded clay.