In situ quantification of biogeochemicalprocesses at cold seeps

This thesis focuses on the interaction between microbiology and geochemistry, and the physical driving forces for the biogeochemical cycles in the near-surface sediments of cold seeps. Cold seeps are extraordinary players in the marine realm, harboring a large biodiversity, and characterized by intense biogeochemical reactions that are stimulated by the advective influx of reduced compounds into the oxidized upper sediment layer. The investigation of rates and pathways of methane, sulfate, and sulfide turnover at cold seeps is environmentally and ecologically relevant as methane is a powerful greenhouse gas and sulfide is toxic for most organisms, but also supports primary production through chemoautotrophic consumption. Due to the high rates of redox processes, chemoautotrophy is highly intense and the seeps are oases of high diverse life. They form ideal natural laboratories to study the link between diversity and energy supply. The main objectives of this thesis were to study the influence of transport on different biogeochemical processes and to determine which parameters control the chemoautotrophy-driven primary production at cold seeps.