Anaerobic Metabolism in Lake Washington Sediments1

Abstract

A method of measuring the dehydrogenasc activity of sediments at 10°C was calibrated by direct microcalorimetry at the same temperature. Field measurements of dehydrogenase activity of sediments in Lake Washington were converted to rates of metabolic heat release by means of the significant regression of dehydrogenase activity on metabolic heat release. Simultaneous field measurements at 10°C of oxygen uptake by undisturbed sediment cores were converted to rates of metabolic heat release by the factor 4.8 cal liberated per milliliter of oxygen consumed.Dehydrogenase activity varies from place to place and differs between layers of the same core. Although there is a general trend of decreasing activity with sediment depth, some subsurface layers have relatively high activity. Dehydrogenase activity, which was detected down to the deepest layers of the sediment cores, 21 to 31 cm, appears to be more a function of plankton remains than of total organic carbon in the sediment. The integrated metabolic heat release based on dchydrogenase activity of the entire core was invariably greater than the metabolic heat release calculated from the rates of oxygen uptake. Thus, it appears that the rate of total oxygen uptake by the sediment surface underestimates benthic community metabolism in the sediment column.A common measure of benthic community metabolism is the rate of uptake of dissolved oxygen by the sediment surface from the overlying water. The rate of respiratory uptake of oxygen is estimated by determining the difference between the rates of total oxygen consumption and residual oxygen uptake after poisoning the overlying water. If total oxygen uptake by the sediment surface is an integrated measure of metabolism in the sediment column (Teal and Kanwisher 1961) , oxygen consumption due to the abiotic oxidation of reduced metal ions, sulfides, and other reduced substances in the sediment should represent

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Measurement of the respiratory electron transport system (ETS) activity in marine sediments:state-of-the-art and interpretation. I. Methodology and review of literature data

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“…Extensive measurements of redox potential in the sediments of the microcosms must also be carried out both with and without the oil exposure. This can be accomplished either with the dehydrogenase assay technique (Pamatmat and Bhagwat, 1973;Vosjan and Olanczuk-Neyman, 1977) or directly with platinum electrodes (Howes et al, 1981).…”