The contributions of temperature and of the input of organic matter in controlling rates of sediment methanogenesis1

The roles of temperature and organic input in determining the rate of methane flux from anoxic sediments were examined under various laboratory and field conditions in two small Michigan lakes. As in other studies, rapid temperature increases in incubating sediment caused immediate increases in methane production rates (avg Q 10 = 2.4). Under in situ conditions, where the hypolimnetic temperature is relatively cold and unchanging for long periods, methane flux was linearly related ⩽ 0.01) to organic input in these two and three other lakes for which data were available. In addition, the proportion of organic input released as methane (47 ± 9%) was close to the theoretical maximum (40 ± 8%) and was not related to temperature. When temperature is constant for long periods, as during summer stratification, CH 4 production adjusts maximally to organic input. When temperature changes rapidly, its effect will be predictably superimposed upon that of organic input.