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Title: Microbial Community Analyses Inform Geochemical Reaction Network Models for Predicting Pathways of Greenhouse Gas Production

Abstract

The mechanisms, pathways, and rates of CO 2 and CH 4 production are central to understanding carbon cycling and greenhouse gas flux in wetlands. Thawing permafrost regions are of particular interest because they are disproportionally affected by climate warming and store large reservoirs of organic C that may be readily converted to CO 2 and CH 4 upon thaw. This conversion is accomplished by a community of microorganisms interacting in complex ways to transform large organic compounds into fatty acids and ultimately CO 2 and CH 4. While the central role of microbes in this process is well-known, geochemical rate models rarely integrate microbiological information. With this, we expanded the geochemical rate model of Neumann et al., (2016, Biogeochemistry 127: 57–87) to incorporate a Bayesian probability analysis and applied the result to quantifying rates of CO 2, CH 4, and acetate production in closed-system incubations of peat collected from three habitats along a permafrost thaw gradient. The goals of this analysis were twofold. First, we integrated microbial community analyses with geochemical rate modeling by using microbial data to inform the best model choice among equally mathematically feasible model variants. Second, based on model results, we described changes in organic carbonmore » transformation among habitats to understand the changing pathways of greenhouse gas production along the permafrost thaw gradient. We found that acetoclasty, hydrogenotrophy, CO 2 production, and homoacetogenesis were the important reactions in this system, with little evidence for anaerobic CH 4 oxidation. There was a distinct transition in the reactions across the thaw gradient. The collapsed palsa stage presents an initial disequilibrium where the abrupt (physically and temporally) change in elevation introduces freshly fixed carbon into anoxic conditions then fermentation products build up over time as the system transitions through the acid phase and electron acceptors are depleted. In the bog, fermentation slows, while methanogenesis increases. In the fully thawed fen, most of the terminal electron acceptors are depleted and the system becomes increasingly methanogenic. This suggests that as permafrost regions thaw and dry palsas transition into wet fens, CH 4 emissions will rise, increasing the warming potential of these systems and accelerating climate warming feedbacks.« less

Authors:
 [1];  [2];  [3];  [3];  [3];  [4];  [3];  [5];  [5];  [1];  [3]
  1. Florida State Univ., Tallahassee, FL (United States). Dept. of Earth, Ocean and Atmospheric Science
  2. Univ. of Washington, Seattle, WA (United States). Dept. of Civil and Environmental Engineering
  3. Ohio State Univ., Columbus, OH (United States). Dept. of Microbiology
  4. Univ. of Arizona, Tucson, AZ (United States). Dept. of Soil, Water, and Environmental Science
  5. Univ. of Queensland, Brisbane (Australia). School of Chemistry and Molecular Biosciences
Publication Date:
Research Org.:
Univ. of Arizona, Tucson, AZ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division
OSTI Identifier:
1504282
Alternate Identifier(s):
OSTI ID: 1506088
Grant/Contract Number:  
SC0010580; SC0016440; SC0010338; AC02-05CH11231; AC05-76RL01830; SC- 0010338
Resource Type:
Journal Article: Published Article
Journal Name:
Frontiers in Earth Science
Additional Journal Information:
Journal Volume: 7; Journal Issue: 59; Journal ID: ISSN 2296-6463
Publisher:
Frontiers Research Foundation
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; greenhouse gas flux; peatlands; organic matter decomposition; climate warming; carbon cycling

Citation Formats

Wilson, Rachel M., Neumann, Rebecca B., Crossen, Kelsey B., Raab, Nicole M., Hodgkins, Suzanne B., Saleska, Scott R., Bolduc, Ben, Woodcroft, Ben J., Tyson, Gene W., Chanton, Jeffrey P., and Rich, Virginia I. Microbial Community Analyses Inform Geochemical Reaction Network Models for Predicting Pathways of Greenhouse Gas Production. United States: N. p., 2019. Web. doi:10.3389/feart.2019.00059.
Wilson, Rachel M., Neumann, Rebecca B., Crossen, Kelsey B., Raab, Nicole M., Hodgkins, Suzanne B., Saleska, Scott R., Bolduc, Ben, Woodcroft, Ben J., Tyson, Gene W., Chanton, Jeffrey P., & Rich, Virginia I. Microbial Community Analyses Inform Geochemical Reaction Network Models for Predicting Pathways of Greenhouse Gas Production. United States. doi:10.3389/feart.2019.00059.
Wilson, Rachel M., Neumann, Rebecca B., Crossen, Kelsey B., Raab, Nicole M., Hodgkins, Suzanne B., Saleska, Scott R., Bolduc, Ben, Woodcroft, Ben J., Tyson, Gene W., Chanton, Jeffrey P., and Rich, Virginia I. Fri . "Microbial Community Analyses Inform Geochemical Reaction Network Models for Predicting Pathways of Greenhouse Gas Production". United States. doi:10.3389/feart.2019.00059.
@article{osti_1504282,
title = {Microbial Community Analyses Inform Geochemical Reaction Network Models for Predicting Pathways of Greenhouse Gas Production},
author = {Wilson, Rachel M. and Neumann, Rebecca B. and Crossen, Kelsey B. and Raab, Nicole M. and Hodgkins, Suzanne B. and Saleska, Scott R. and Bolduc, Ben and Woodcroft, Ben J. and Tyson, Gene W. and Chanton, Jeffrey P. and Rich, Virginia I.},
abstractNote = {The mechanisms, pathways, and rates of CO2 and CH4 production are central to understanding carbon cycling and greenhouse gas flux in wetlands. Thawing permafrost regions are of particular interest because they are disproportionally affected by climate warming and store large reservoirs of organic C that may be readily converted to CO2 and CH4 upon thaw. This conversion is accomplished by a community of microorganisms interacting in complex ways to transform large organic compounds into fatty acids and ultimately CO2 and CH4. While the central role of microbes in this process is well-known, geochemical rate models rarely integrate microbiological information. With this, we expanded the geochemical rate model of Neumann et al., (2016, Biogeochemistry 127: 57–87) to incorporate a Bayesian probability analysis and applied the result to quantifying rates of CO2, CH4, and acetate production in closed-system incubations of peat collected from three habitats along a permafrost thaw gradient. The goals of this analysis were twofold. First, we integrated microbial community analyses with geochemical rate modeling by using microbial data to inform the best model choice among equally mathematically feasible model variants. Second, based on model results, we described changes in organic carbon transformation among habitats to understand the changing pathways of greenhouse gas production along the permafrost thaw gradient. We found that acetoclasty, hydrogenotrophy, CO2 production, and homoacetogenesis were the important reactions in this system, with little evidence for anaerobic CH4 oxidation. There was a distinct transition in the reactions across the thaw gradient. The collapsed palsa stage presents an initial disequilibrium where the abrupt (physically and temporally) change in elevation introduces freshly fixed carbon into anoxic conditions then fermentation products build up over time as the system transitions through the acid phase and electron acceptors are depleted. In the bog, fermentation slows, while methanogenesis increases. In the fully thawed fen, most of the terminal electron acceptors are depleted and the system becomes increasingly methanogenic. This suggests that as permafrost regions thaw and dry palsas transition into wet fens, CH4 emissions will rise, increasing the warming potential of these systems and accelerating climate warming feedbacks.},
doi = {10.3389/feart.2019.00059},
journal = {Frontiers in Earth Science},
issn = {2296-6463},
number = 59,
volume = 7,
place = {United States},
year = {2019},
month = {3}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.3389/feart.2019.00059

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