Anaerobic metabolism of particulate organic matter in the sediments of a hypereutrophic lake*

Abstract

The anaerobic decomposition of particulate organic tnatter (POM) was examined in the anoxic pelagic sediments of hypereutrophic Wintergreen Lake. Degradation of sedimented POM occurred rapidly as shown by increased production and release of ammonia, hydrogen sulphide, volatile fatty acids and methane from the sediments 2-3 weeks after large inputs of organic matter. Maximum concentrations of most metabolites were found at the sediment-water interface, indicating that the initial anaerobic degradation of freshly deposited POM occurred at this site. The absence of the inorganic electron acceptors, nitrate and sulphate, suggested that fermentation and methanogenesis were the major anaerobic processes involved in the dissimilation of organic matter in these sediments during stratified periods. The amount of carbon input converted to methane in the sediments was determined from May to early November 1976 and 1977. Carbon output as methane was measured by quantifying methane lost from the sediments by ebullition and by estimating soluble methane lost to the water column by diffusion. Total methane release during summer stratification accounted for 34% of the particulate organic carbon input to the sediments in 1976 and 44^/^ in 1977. Methane release was directly related to the rate of sedimentation of POM. However, methane production was temporarily inhibited following high rates of sedimentation in 1976, suggesting that the rate of organic loading may be an important factor controlling anaerobic decomposition in these sediments.

Model for the distribution of sulfate reduction and methanogenesis in freshwater sediments

“…Acetate concentrations in the methanogenic zone fell within the wide range of acetate concentrations that have been reported for freshwater methanogenic sediments (MOLONGOSKI and KLUG, 1980;WINFREY and ZEIKUS, 1979;HORDUK and CAPPENBERG, 1983). Thus, the predicted increase in acetate concentration concomitant with a shift from sulfate reduction to methane production is consistent with existing data but has yet to be adequately documented in field studies on freshwater sediments.…”

Depositional fluxes of metals and phytoplankton in Windermere as measured by sediment traps1

“…The close link between rates of organic matter sedimen-tation and microbial decomposition has often been demonstrated (e.g. Kelly and Chynoweth 198 1;Molongoski and Klug 1980) and the intact cells reaching the sediment probably contain extremely labile organic material.…”

Electron flow via sulfate reduction and methanogenesis in the anaerobic hypolimnion of Lake Mendota1

“…Many studies have dealt with methane formation and the quantitative importance of methanogenesis in anaerobic carbon cycling in eutrophic lakes (e.g. Fallon et al 1980;Molongoski and Klug 1980;Robertson 1979;Rudd and Hamilton 1978;Strayer and Tiedje 1978 Stuiver (1967), andWinfrey andZeikus (1979b) suggest that high rates of sulfate reduction occur in a narrow zone at the sediment surface. Stuiver's (1967) data indicate that the net sulfate depletion in the anoxic hypolimnion of Linsley Pond can be attributed to bacterial sulfate reduction.…”