In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO
4
2– reduction rates in the sediment, (2) depletion of SO
4
2– in the overlying water column and (3) release of
35S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO
4
2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core
35SO
4
2– injection. Rates of SO
4
2– consumption in the overlying water were estimated by changes in SO
4
2– concentration over time in
in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m
–2 d
–1. Rates of SO
4
2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m
–2 d
–1 (November) to 0.43–1.81 mmol m
–2 d
–1 (July, August and April). Maximum rates of oxidation to SO
4
2– in July 1990 estimated by combination of SO
4
2– reduction rates and rates of
in situ SO
4
2– uptake in the enclosed water column were 10.3 and 10.5 mmol m
–2 d
–1 at an organic rich and at a sandy site respectively.Experiments with
35S
2– and
35SO
4
2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO
4
2– and (2) the presence of mainly non SO
4
2–-S derived from reduced S transported from the sediment into the overlying water. A
35S
2– tracer experiment showed that about 7% of
35S
2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author
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