Estimating changes of isotopic fractionation based

Authors: V A Vavilin

Publish Date: 2012/09/26

Volume: 103, Issue: 2, Pages: 375-383

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Abstract

Changes in natural isotopic composition may be used to reveal metabolic pathways of substrate transformation by microbial communities Vavilin in Ecol Model 24084–92 2012b Anaerobic oxidation of methane AOM by sulfate has been described using a mathematical model based on chemical kinetics microbial dynamics and equations for 13C isotope accumulation in products as well as their redistribution between substrate and products Experimental data for two batch cultures that originated from microbial mats covering methane seep chimneys in the Black Sea previously obtained by Seifert et al Org Geochem 371411–1419 2006 and Holler et al Env Microbiol Reports 15370–376 2009 were used to model AOM During longtime incubation changes of isotope signatures in CH4 showed that in the Seifert et al batch tests low methane concentration in contrast to the Holler et al batch tests high methane concentration methane production occurred along with methane oxidation In accordance with the model apparent zero and firstorder kinetics of methane oxidation were valid for the Holler et al and Seifert et al batch tests respectively The observed change of delta 13textCH 4 was explained by microbial kinetics reflecting that the rate is lower for heavy substrate microbial utilization when compared to light substrate microbial utilization The model showed that small amounts of methanogenesis will change the carbon isotopic composition of methane because biogenic methane has a distinct isotopic composition and due to the large difference between the maximum specific rates of methane oxidation and production The estimated biomass doubling time of methaneoxidizers for high and low methane concentration was 408/126 days and 4640/1160 days respectively depending on the value of the halfsaturation constant K S 5 and 20 mM

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