A method for the analysis of acetate turnover in a coastal marine sediment

Abstract

The concentrations of volatile fatty acids were measured in the pore water of sediment from the Limfjorden, Denmark. The pore water was freeze-dried and the acids, which were redissolved in formic acid, were analyzed by gas chromatography on a Carbopack column. The limit of detection was 0.1 μmol l⁻¹ pore water. The concentration ranges (μmol l⁻¹ pore water) were as follows: 0.1 to 6.0 for acetate; 14C-acetate were measured at 2 cm depth intervals in sediment strata (0 to 10 cm). The rate constant for acetate turnover at 4 to 6 cm depth did not vary greatly with season, 2.1 h⁻¹, SD 0.6 for 7 values. In spring, the rate constants were highest in the 0 to 2 cm stratum and decreased with sediment depth. The calculated rates for acetate turnover of 7.2 mmol m⁻² day⁻¹ for early spring (2°C) and of 19.6 mmol m⁻² day⁻¹ for late autumn (7°C) were higher than would be expected from published values for carbon oxidation by sulfate in these sediments.