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Radioisotope tracer studies of inorganic carbon and Ca in microbially derived CaCO3

Kimberly K. Yates·Lisa L. Robbins
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Abstract

Microbial calcification significantly impacts the cycling and deposition of inorganic carbon. This research employs 45 Ca and 14 C techniques as radioisotopic tracers to examine the role of cellular cycling of Ca 2+ and inorganic carbon in CaCO 3 precipitation by the unicellular green alga Nannochloris atomus. Implications of the effects of these physiological aspects on CaCO 3 precipitation and the effects of microbial calcification on CaCO 3 δ 13 C ratios are discussed. Results from pulse/chase experiments indicate that intracellular Ca 2+ is incorporated into extracellular CaCO 3 . Intracellular inorganic carbon leaks from cells within 10 to 12 s after injection of unlabelled NaHCO 3 , providing a source of inorganic carbon for extracellular CaCO 3 . Cellular expulsion of calcium plays a key role in increasing the CaCO 3 saturation state at the site of calcification. The δ 13 C ratios of microbial carbonates may vary depending on the amount of photorespiratory CO 2 incorporated.

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Kimberly K. Yates, Lisa L. Robbins. 1999. Radioisotope tracer studies of inorganic carbon and Ca in microbially derived CaCO3. https://doi.org/10.1016/s0016-7037(98)00297-x

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