Page 163 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

incubations, the CH4 production rates were higher at 10°C than at 4°C (Table 1). At both temperatures, the substrate additions induced higher methanogenic activity over the control except for H2/MeOH. The highest methanogenesis rates were observed with TMA as substrate with 6.6 ± 0.01 μmol CH4 gdw-1 d-1 and 8.5 ± 0.3 μmol CH4 gdw-1 d-1 at 4°C and 10°C respectively (Table 1). This was followed by acetate, being 3% higher at 10°C compared to 4°C. For both incubations, the total CH4 production was not significantly different (two-sided t-test; p>0.05).
25 400 20 15 10 300 50
4oC
10oC TMA
4oC Acetate 10oC
4oC H2/CO2 0 10 20 30 40 50 60 10oC
4oC Control
Figure 2. CH4 production in batch incubation assays of thermokarst lake sediment slurry at 4°C and 7 10°C amended with different methanogenic substrates. Each data point represents the average of 3 incubations. Substrates: trimethylamine (TMA), acetate, H2/methanol (MeOH), H2/CO2, the control
contained only the sediment slurry. Error bars indicate standard deviation of the mean. Zoom in depicts
the H2/CO2 cultures for 0-64 days.
Table 1. Methanogenesis rates and total methane production measured in soil slurries incubated with 2 mM trimethylamine (TMA), 2 mM Acetate, 2 mM methanol (MeOH) with 8 mM H2, and 8 mM H2 with 2 mM CO2. As control, sediment slurries were incubated without addition substrate. Gas measurements were performed in triplicate, and rates were calculated for the linear phase. Numbers between brackets display standard deviation of the mean.
μmol CH4 gdw-1
200
100 10oC
00 50 100 150 200 250 Time (days)
Maximum methane production rate Substrate (μmol CH4 gdw-1 d-1)
Total methane production (μmol CH4 gdw-1)
4°C
TMA 6.6 ± 0.01
Acetate 3.4 ± 0.4 H2/CO2* 0.7 ± 0.05 H2/MeOH 0.3 ± 0.2 Control 1.0 ± 0.07
*64 days of incubation
10°C
8.7 ± 0.3 4.8 ± 0.4 1.4 ± 0.1 0.7 ± 0.04 1.7 ± 0.2
4°C 420±9 268±2 13±1 10 ± 0.3 33 ± 2
10°C 409 ± 11 284 ± 6 21 ± 2 14 ± 1 35 ± 2
4oC H /MeOH 10oC 2
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