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Calcite and dolomite dissolution rates in the context of microbe–mineral surface interactions
Author(s) -
DAVIS K. J.,
NEALSON K. H.,
LÜTTGE A.
Publication year - 2007
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/j.1472-4669.2007.00112.x
Subject(s) - dissolution , calcite , dolomite , carbonate , mineral , mineralogy , chemistry , weathering , geology , chemical engineering , geochemistry , organic chemistry , engineering
Although microbes have been shown to alter the dissolution rate of carbonate minerals, a mechanistic understanding of the consequences of microbial surface colonization on carbonate dissolution has yet to be achieved. Here we report the use of vertical scanning interferometry (VSI) to study the effect of Shewanella oneidensis MR‐1 surface colonization on the dissolution rates of calcite (CaCO 3 ) and dolomite (CaMg(CO 3 ) 2 ) through qualitative analysis of etch pit development and quantitative measurements of surface‐normal dissolution rates. By quantifying and comparing the significant processes occurring at the microbe–mineral interface, the dominant mechanism of mineral dissolution during surface colonization was determined. MR‐1 attachment under aerobic conditions was found to influence carbonate dissolution through two distinct mechanistic pathways: (1) inhibition of carbonate dissolution through interference with etch pit development and (2) excavation of carbonate material at the cell–mineral interface during irreversible attachment to the mineral surface. The relative importance of these two competing effects was found to vary with the solubility of the carbonate mineral studied. For the faster‐dissolving calcite substrates, inhibition of dissolution by attachment and subsequent extracellular polysaccharide (EPS) production was the dominant effect associated with MR‐1 surface colonization. This interference with etch pit development resulted in a 40–70% decrease in the surface normal dissolution rate relative to cell‐free controls, depending primarily on the concentration of cells in solution. However, in the case of the slower‐dissolving dolomite substrates, carbonate material displaced during the entrenchment of cells on the surface far outweighed the abiotic dissolution rate. Therefore, during the initial stages of surface colonization, dolomite dissolution rates were actually enhanced by MR‐1 attachment. This study demonstrates the dynamic and competitive relationship between microbial surface colonization and mineral dissolution that may be expected to occur in natural environments.