Methane production and sulfate reduction in profundal sediments in Lake Kizaki, Japan

Abstract

The rates of methane production and sulfate reduction were investigated in the profundal sediments (a water depth of 29 m) of Lake Kizaki from April 1992 to July 1994. The rate of methane production on an area basis ranged from 0.81 to 5.55mmol m-2 day-1 (average 1.89 mmol m-2 day-1). The most active layer of methane production was often found in the deepest layer (9-12 cm) examined. Relatively high activities of methane production were observed from summer to early autumn. The sulfate reduction rate on an area basis was from 0.028 to 0.26 mmol m-2 day-1 (average 0.119 mmol m-2 day-1). The rate was highest in the surface layer and decreased with depth, in contrast to methane production. The rate of sulfate reduction was relatively high in spring and summer and low in late autumn and winter. The contribution of methane production to anaerobic mineralization was much greater than that of sulfate reduction due to a low level of sulfate. Methane production seemed to be mainly limited by low temperature, but not by substrate supply.