Dynamics of bacterial sulphate reduction in the sediment of Lake Vechten

Abstract

As a result of analytical difficulties in determining the pool sizes of sulphate in interstitial water in freshwater sediments, data on the quantification of sulphate reduction by existing a s S radiotracer methods or mathematical modelling are essentially lacking for low-sulphate environments. Recently, we have developed a method to determine sulphate in freshwater-sediment interfaces by Indirect Photometric Chromatography (IPC), which gives well-defined sulphate profiles in the IxM-range of the sediments of Lake Vechten (Hordijk et al., 1984; Hordijk and Cappenberg, 1985). IPC and microdistillation enabled a simultaneous measurement of sulphate depletion and sulphide production in the upper 3 cm of freshwater sediments (Hordijk et al., 1985). The simultaneous measurement of sulphate depletion and sulphide production rates provided added insights into microbial sulphur metabolism. The lower sulphate reduction rates as derived from the production of acid volatile 35 S only, were explained by a conversion of this pool to an undistillable fraction during incubation. In Lake Vechten sulphate-reducing activities were correlated with the seasonal fluctuation of the sulphate concentration in the lake. The rapid, nearly linear depletion of added sulphate from 200 ~tM (10 x natural concentration) till below 2 laM indicated that sulphate reduction in freshwater sediments like Lake Vechten are mainly limited by the absence of sulphate rather than by the lack of potential electron donors as lactate and acetate (Hordijk and Cappenberg, 1983).