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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.
