Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Biogeosciences, 13, 3319-3329, 2016
https://doi.org/10.5194/bg-13-3319-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
07 Jun 2016
Temperature-mediated changes in microbial carbon use efficiency and 13C discrimination
Christoph A. Lehmeier1, Ford Ballantyne IV1,a, Kyungjin Min1, and Sharon A. Billings1 1Department of Ecology and Evolutionary Biology, Kansas Biological Survey, University of Kansas, 2101 Constant Ave., Lawrence, KS 66047, USA
anow at: Odum School of Ecology, University of Georgia, 140 E. Green St., Athens, GA 30602, USA
Abstract. Understanding how carbon dioxide (CO2) flux from ecosystems feeds back to climate warming depends in part on our ability to quantify the efficiency with which microorganisms convert organic carbon (C) into either biomass or CO2. Quantifying ecosystem-level respiratory CO2 losses often also requires assumptions about stable C isotope fractionations associated with the microbial transformation of organic substrates. However, the diversity of organic substrates' δ13C and the challenges of measuring microbial C use efficiency (CUE) in their natural environment fundamentally limit our ability to project ecosystem C budgets in a warming climate. Here, we quantify the effect of temperature on C fluxes during metabolic transformations of cellobiose, a common microbial substrate, by a cosmopolitan microorganism growing at a constant rate. Biomass C specific respiration rate increased by 250 % between 13 and 26.5 °C, decreasing CUE from 77 to 56 %. Biomass C specific respiration rate was positively correlated with an increase in respiratory 13C discrimination from 4.4 to 6.7 ‰ across the same temperature range. This first demonstration of a direct link between temperature, microbial CUE, and associated isotope fluxes provides a critical step towards understanding δ13C of respired CO2 at multiple scales, and towards a framework for predicting future ecosystem C fluxes.

Citation: Lehmeier, C. A., Ballantyne IV, F., Min, K., and Billings, S. A.: Temperature-mediated changes in microbial carbon use efficiency and 13C discrimination, Biogeosciences, 13, 3319-3329, https://doi.org/10.5194/bg-13-3319-2016, 2016.
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