TY - JOUR
T1 - Distinguishing Biotic and Abiotic Iron Oxidation at Low Temperatures
AU - St Clair, Brian
AU - Pottenger, Justin
AU - Debes, Randall
AU - Hanselmann, Kurt
AU - Shock, Everett
N1 - Funding Information:
*E-mail: bstclair@mtech.edu (Montana address). ORCID Brian St Clair: 0000-0002-5843-0754 Present Address #CDepartment of Chemistry and Geochemistry, Montana Technological University, 1300 W Park St., Butte, MT 59701. Funding This work was funded by the National Science Foundation (Grant EAR-1529963). Notes The authors declare no competing financial interest.
Publisher Copyright:
© 2019 American Chemical Society.
Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.
PY - 2019/6/20
Y1 - 2019/6/20
N2 - The rates of microbial and abiotic iron oxidation were determined in a variety of cold (T = 9-12 °C), circumneutral (pH = 5.5-9.0) environments in the Swiss Alps. These habitats include iron-bicarbonate springs, iron-arsenic-bicarbonate springs, and alpine lakes. Rates of microbial iron oxidation were measured up to a pH of 7.4, with only abiotic processes detected at higher pH values. Iron oxidizing bacteria (FeOB) were responsible for 39-89% of the net oxidation rate at locations where biological iron oxidation was detected. Members of putative iron oxidizing genera, especially Gallionella, are abundant in systems where biological iron oxidation was measured. Geochemical sampling suites accompanying each experiment include field data (temperature, pH, conductivity, dissolved oxygen, and redox sensitive solutes), solute concentrations, and sediment composition. Dissolved inorganic carbon concentrations indicate that bicarbonate and carbonate are typically the most abundant anions in these systems. Speciation calculations reveal that ferrous iron typically exists as FeCO3(aq), FeHCO3+, FeSO4(aq), or Fe2+ in these systems. The abundance of ferrous carbonate and bicarbonate species appears to lead to a dramatic increase in the abiotic rate of reaction compared to the rate expected from chemical oxidation in dilute solution. This approach, integrating geochemistry, rates, and community composition, reveals locations and geochemical conditions that permit microbial iron oxidation and locations where the abiotic rate is too fast for the biotic process to compete.
AB - The rates of microbial and abiotic iron oxidation were determined in a variety of cold (T = 9-12 °C), circumneutral (pH = 5.5-9.0) environments in the Swiss Alps. These habitats include iron-bicarbonate springs, iron-arsenic-bicarbonate springs, and alpine lakes. Rates of microbial iron oxidation were measured up to a pH of 7.4, with only abiotic processes detected at higher pH values. Iron oxidizing bacteria (FeOB) were responsible for 39-89% of the net oxidation rate at locations where biological iron oxidation was detected. Members of putative iron oxidizing genera, especially Gallionella, are abundant in systems where biological iron oxidation was measured. Geochemical sampling suites accompanying each experiment include field data (temperature, pH, conductivity, dissolved oxygen, and redox sensitive solutes), solute concentrations, and sediment composition. Dissolved inorganic carbon concentrations indicate that bicarbonate and carbonate are typically the most abundant anions in these systems. Speciation calculations reveal that ferrous iron typically exists as FeCO3(aq), FeHCO3+, FeSO4(aq), or Fe2+ in these systems. The abundance of ferrous carbonate and bicarbonate species appears to lead to a dramatic increase in the abiotic rate of reaction compared to the rate expected from chemical oxidation in dilute solution. This approach, integrating geochemistry, rates, and community composition, reveals locations and geochemical conditions that permit microbial iron oxidation and locations where the abiotic rate is too fast for the biotic process to compete.
KW - Gallionella
KW - chemical speciation
KW - iron oxidizing bacteria
KW - iron redox cycling
KW - metal bicarbonates
KW - metal carbonates
KW - rate experiments
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U2 - 10.1021/acsearthspacechem.9b00016
DO - 10.1021/acsearthspacechem.9b00016
M3 - Article
AN - SCOPUS:85067046338
SN - 2472-3452
VL - 3
SP - 905
EP - 921
JO - ACS Earth and Space Chemistry
JF - ACS Earth and Space Chemistry
IS - 6
ER -