Page 120 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Chapter 5. Early Holocene carbon storage and microbial activity in North Sea peats
active CH4 production upon incubation, with a strong increase in rates of production upon methylated substrate amendment (Fig. 5). Molecular analysis showed that methanogens were present at all four assessed sites: Westland, Senator Westphal, Max Gundelach and Vittorio (Fig. 6).
1 00 80 60
TMA
H2/MeOH
H2/CO2
Acetate
0 .04 0 .03 0 .02 0 .01
0
0 20 40 60 80
40 MPH TMB
20
00 10 20 30 40 50 60 70 80 Time [days]
Control
Figure 5. Methane production in batch incubation assays of peat sediment slurries. Methane contents are given as CH4 produced per cm3 of original peat sediment over the course of 75 days. Substrates: trimethylamine (TMA), hydrogen and methanol (H2/MeOH), hydrogen and CO2 (H2/CO2), acetate, methoxyphenol (MPH), trimethoxybenzoate (TMB) and an anaerobic control incubation without substrate amendment (Control). Data points represent the average of triplicate measurements on triplicate incubations. Error bars indicate the standard deviation of the mean. The insert depicts a zoom in on the CH4 concentrations excluding the incubations on TMA and H2/MeOH.
Methane production in the unamended control incubation was very low, indicating that most, if not all, of the labile organic matter fraction of the peat sediments has already been mineralized. Methane accumulation was observed subsequent to the addition of methylated substrates (Fig. 5) after a lag phase of two weeks, indicating that the CH4-producing microbial community could be quickly metabolically revived. In the incubation with H2 and MeOH, CH4 production was solely linked to MeOH, which was confirmed upon amendment with MeOH after depletion of H2.
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Gas conc. [μmol CH4 cm-3 sed.]