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Electron transfer of dissolved organic matter and its potential significance for anaerobic respiration in a northern bog
Author(s) -
HEITMANN TOBIAS,
GOLDHAMMER TOBIAS,
BEER JULIA,
BLODAU CHRISTIAN
Publication year - 2007
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2007.01382.x
Subject(s) - dissolved organic carbon , environmental chemistry , chemistry , methanogenesis , peat , organic matter , anaerobic respiration , heterotroph , carbon dioxide , sulfate , redox , oxygen , anaerobic exercise , inorganic chemistry , methane , ecology , geology , biology , physiology , paleontology , organic chemistry , bacteria
We investigated electron transfer processes of dissolved organic matter (DOM) and their potential importance for anaerobic heterotrophic respiration in a northern peatland. Electron accepting and donating capacities (EAC, EDC) of DOM were quantified using dissolved H 2 S and ferric iron as reactants. Carbon turnover rates were obtained from porewater profiles (CO 2 , CH 4 ) and inverse modeling. Carbon dioxide was released at rates of 0.2–5.9 mmol m −2 day −1 below the water table. Methane (CH 4 ) formation contributed <10%, and oxygen consumption 2% to 40%, leaving a major fraction of CO 2 production unexplained. DOM oxidized H 2 S to thiosulfate and was reduced by dissolved ferric iron. Reduction with H 2 S increased the subsequently determined EDC compared to untreated controls, indicating a reversibility of the electron transfer. In situ redox capacities of DOM ranged from 0.2 to 6.1 mEq g −1 C (EAC) and from 0.0 to 1.4 mEq g −1 C (EDC), respectively. EAC generally decreased with depth and changed after a water table drawdown and rebound by 20 and −45 mEq m −2 , respectively. The change in EAC during the water table fluctuation was similar to CH 4 formation rates. In peatlands, electron transfer of DOM may thus significantly contribute to the oxidation of reduced organic substrates by anaerobic heterotrophic respiration, or by maintaining the respiratory activity of sulfate reducers via provision of thiosulfate. Part of the anaerobic electron flow in peat soils is thus potentially diverted from methanogenesis, decreasing its contribution to the total carbon emitted to the atmosphere.