My research interests are generally in the fields of marine biogeochemistry and microbial ecology with a present focus on the deep sub-seafloor biosphere. Through collaborations in the Center for Geomicrobiology I study the processes and microbiology of sulfur and methane cycling in marine sediments. Important questions include, how do the microorganisms thrive at extremely low energy flux and how may the microbial processes and the organisms differ from those of the surface world. A recent result was the discovery of a "cryptic sulfur cycle" in the methane zone which explains the deep occurrence of sulfate reducing microorganisms. In a multidisciplinary project (Baltic Gas) on methane cycling in the Baltic Sea we study the controls on methane fluxes and their sensitivity to predicted climate change.