Microbial cycling of iron in acidic fens
DFG FOR 562 TP 2: (2008-2011)
From 04/2008 to 12/2011Principal Investigator: Kirsten Küsel
Staff: Martina Herrmann, Anke Hädrich
The manipulation experiments of 2006 and 2007 indicated that increased peat aeration at the fen Schlöppnerbrunnen did not eliminate the critical mechanism restricting the re-release of CO2 to the atmosphere as predicted by the enzymic latch hypothesis. However, manipulation renewaled the pool of alternative electron acceptors and shifted the electron flow from CH4 formation to alternative processes. Acetate was formed in soil microcosms, but the stimulation of CH4 formation or Fe(III) reduction was small. Surprisingly not the rate of Fe(II) formation was enhanced after rewetting but the time period was elongated, and maximum amount of Fe(II) formed increased in all soil depths suggesting a mobilization and subsequent oxidation of Fe(II) from deeper reduced soil horizons. Thus, the hypothesis of this project is that increased drying and rewetting events favor microbial Fe(III) reduction especially in peat layers below the surface due to iron minerals deposited by Fe(II) oxidizing bacteria. The main goals of project 2 are (1) to determine if drying and rewetting events affect the abundance of the active Fe(III)-reducing populations, (2) to estimate to which extent Fe(II)-oxidizing bacteria are involved in the deposition of iron minerals, and (3) to elucidate the microbial population involved in the oxidation of acetate.