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Abstract

The present chapter deals with the biogeochemical transformations of sulfur within marine sediments during early diagenesis. The term ‘early diagenesis’ refers to the whole range of postdepositional processes that take place in aquatic sediments coupled either directly or indirectly to the degradation of organic matter. We focus on the processes that drive sulfate reduction together with the manifold associated biotic and abiotic reactions that make up the sedimentary sulfur cycle. Furthermore, we will give an overview of the quantitative significance of microbial sulfate reduction in the remineralization of organic matter and oxidation of methane in different depositional environments and discuss the often observed discrepancy between sulfate reduction rates deduced from radiotracer methods and those calculated from pore-water concentration profiles and/or solid-phase sulfur data.