Division of Biology, Faculty of Science, University of Zagreb
Abstract
The involvement of cyanobacteria in the precipitation process forming calcium carbonate was studied in samples collected at a geothermal spring located in an area close to Puente del Inca (Mendoza, Argentina). In the summer season profuse cyanobacterial growth is
observed at Puente del Inca in areas exposed to sunlight and over which thermal water flows. Differences in cellular structure allowed the recognition of strains of Oscillatoria, Spirulina, Plectonema, and Nostoc, Oscillatoria and Spirulina being the dominant species.
The mass cultivation of Oscillatoria sp. was obtained using a new culture medium (BW3) PI which was formulated according to the chemical composition of the thermal water. On a dry-weight basis the biomass concentration was 0.88 g L–1 at pH 7.5 and 0.44 g L–1
with a free pH evolution after 11 days of incubation. The increase of pH associated with Oscillatoria sp. growth triggered calcium carbonate precipitation at values higher than 8.1. The events observed under laboratory conditions are likely to occur in situ as a consequence
of cyanobacterial growth in the saturated thermal water of Puente del Inca
