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ABSTRACT
In the present study, laboratory precipitation experiments using similar water chemistry and two different bacterial cultures from Lake Acıgöl sediments, a hypersaline lake in Turkey, were performed to reproduce mineral assemblages similar to those found in the lake. Two different bacterial cultures induce various calcium/magnesium carbonates precipitation under all the experimental conditions (solid vs. liquid): Hydromagnesite, dypingite, huntite, monohydrocalcite, and aragonite. The geochemical program PHREEQC was used to calculate the mineral saturation indexes in the cultures and in lake water. Carbonate mineral assemblages identified in the experiments seem to be independent of the type of microorganisms but rather controlled by the chemical composition and physical conditions of the media. The relative amounts of monohydrocalcite, hydromagnesite, and dypingite are controlled by varying sulfate concentration from 0 to 56 mM. This demonstrates a kinetic effect that could similarly affect the mineral assemblage in the lake. Also the spherical morphology of hydromagnesite points to growth of these minerals under partial inhibition in the brine under high concentrations of ions and organic polymers produced by the microbial communities. As reproduced by the culture experiments, the authigenic carbonate mineral assemblage of Lake Acıgöl most likely results from interplay of ionic composition of the brine and microbial effects.
Acknowledgments
The authors thank ALKIM chemistry for providing assistance in the field and EMCOL for providing core sediment samples.
Funding
This work was supported by TUBITAK (the Scientific and Technological Research Council of Turkey) grant to N. BALCI (113Y464). P. Meister was supported by the Marie-Curie Intra European Fellowship, Project TRIADOL.
