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

Abstract

AhstructThe 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 Q10 = 2.4). Under in situ conditions, where the hypolimnetic temperature is relatively cold and unchanging for long periods, methane flux was linearly related (P < 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 + 94 ) o 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, production adjusts maximally to organic input, When temperature changes rapidly, its effect will be predictably superimposed upon that of organic input.

Long‐term changes in the areal hypolimnetic oxygen deficit (AHOD) of Onondaga Lake: Evidence of sediment feedback

“…2C), is rare, if not unique. The downward flux of POC is an acknowledged metric of primary production (Molongoski and Klug 1980;Kelly and Chynoweth 1981), and it is the link connecting metabolism between the trophogenic and tropholytic zones. The abrupt, steplike, decrease in POC df following industry closure has provided a rare opportunity to resolve and characterize the effects on hypolimnetic DO resources.…”

Effects of lake acidification on rates of organic matter decomposition in sediments

“…The rate of change in mass was always linear (P > 0.95) and was calculated by linear regression. Some DIC and CH4 was lost to water above 12 m; these losses were calculated (Kelly et al 1982) and added to the change in mass. The corrections were always ~20% of the change in mass.…”

“…During summer stratification, decomposition rates in the hypolimnion of Lake 223 were estimated as described by Kelly et al (1982). Briefly, decomposition rate was estimated by summing the rates of accumulation of DIC and CH4 below the depth of light penetration.…”

“…Also, some anoxic microorganisms' involved in decomposition are able to neutralize acid (Schindler et al 1980;Kelly et al 1982) so a decrease in their activity would reduce the capacity for acid neutralization in lakes. These concerns have been strengthened in some cases by small-scale laboratory studies and by studies of weight loss of leaf litter in bags (Andersson et al 1978;Gahnstrdm et al 1980;Traaen 1980;McKinley and Vestal 1982).…”

Modeling the impediment of methane ebullition bubbles by seasonal lake ice

“…On days during the study period when temperature measurements were available, we applied the average temperature from both measurement locations in the model; when temperature measurements were unavailable, we used Julian day temperature averages calculated from data from the entire measurement period. We used a Q 10 value for methanogenesis of 2.4 from Kelly and Chynoweth (1981) to scale the average diffusive flux calculated from both sediment cores from Vault Lake on each day of the study period, depending on the sediment temperature in Goldstream Lake. We assumed that the diffusive flux calculated from measurements was representative of the in situ diffusive flux at 2 • C, the temperature of the cores before analysis.…”