2 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 fres hwater marsh (USDA: typic fluvaquent). Methanogenic bacteria were foun d in oxic as well as in anoxic soil layers. Most probable number count s varied from 1.4x10(2) to 2.5x10(6) bacteria g(-1) fresh weight. Meth ane production at different temperatures (5 degrees C, 10 degrees C, 1 5 degrees C, 20 degrees C) was studied with undisturbed soil cores. Th e highest methane production rates were measured at 10 degrees C (0.31 nmol h(-1) (g d.w.)(-1)) and 20 degrees C (0.58 nmol h(-1) (g d.w.)(- 1)). Incubation experiments with disturbed soil material showed two op tima of methane production at 10 degrees C and in the mesophilic tempe rature range. Experiments with different substrates indicate that at 1 0 degrees C acetate serves as substrate while at higher temperatures h ydrogen is the main energy source for methanogens.