Two temperature optima of methane production in a typical soil of the Elbe river marshland
The soil of the Elbe river marshland was classified as calcareous freshwater marsh (USDA: typic fluvaquent). Methanogenic bacteria were found in oxic as well as in anoxic soil layers. Most probable number counts varied from 1.4×102 to 2.5×106 bacteria g−1 fresh weight. Methane production at different temperatures (5°C, 10°C, 15°C, 20°C) was studied with undisturbed soil cores. The highest methane production rates were measured at 10°C (0.31 nmol h−1 (g d.w.)−1) and 20°C (0.58 nmol h−1 (g d.w.)−1). Incubation experiments with disturbed soil material showed two optima of methane production at 10°C and in the mesophilic temperature range. Experiments with different substrates indicate that at 10°C acetate serves as substrate while at higher temperatures hydrogen is the main energy source for methanogens.