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Abstract

The turnover and ecological role of the sulfur intermediate tetrathionate (S 4 O 6 2- ) in the marine environment is still poorly understood. Tetrathionate turnover and its effect on bacterial growth in sandy sediment were investigated under anoxic and oxic conditions. Surface sediment was collected from Janssand, an intertidal sandflat in the German Wadden Sea, and fed with tetrathionate in packed flow through columns and batch experiments. A new High Performance Liquid Chromatography (HPLC) method was used to simultaneously determine tetrathionate and thiosulfate concentrations over time. Changes in the relative abundance of Bacteria, Gamma- and Deltaproteobacteria were analyzed with Fluorescence In Situ Hybridization with Catalyzed Reporter Deposition (CARD- FISH). It was shown that tetrathionate is consumed mainly by sediment-affiliated microbial communities both under oxic and anoxic conditions. Under oxic conditions, oxidation of tetrathionate is an important process and turnover rates exceed those in reduced sediments. With increasing oxygen limitation in the sediment pore-water, tetrathionate reduction, and to a lesser extent disproportionation, play an increasingly important role. Subsequent chemical degradation of the formed thiosulfate stagnates when the sediment becomes reduced. Although the ecological role of tetrathionate reduction, oxidation and disproportionation remains largely unanswered, fast and immediate turnover rates indicate that tetrathionate is an important intermediate in the marine sedimentary sulfur cycle.