Over the last decade increasing attention has been drawn to gas hydrates in submarine environments. Interests were rising from different directions including (1) the assessment of methane hydrates as an energy source, (2) the submarine sequestration of CO2 hydrates, (3) the estimation of the potential danger of gas hydrates for climate change, and (4) the role of gas hydrates in natural phenomena such as chemosynthetic cold-seep habitats. Most of these studies, however, depend on the basic understanding of gas hydrate behavior in its natural environment. In this session, we aim to bring together scientists from the fields of geology, physical chemistry, isotope geochemistry, biogeochemistry, and numerical modeling to discuss recent knowledge on gas hydrate properties and reactions in marine sediments. Questions we would like to address include: How and where do gas hydrates form in marine sediments? How does gas hydrate formation change the geochemistry of sediments? What are the gas and fluid sources of hydrates and how are they related to changes in porewater geochemistry? What causes gas hydrate destabilization? Which importance has the gas hydrate composition and structure for gas hydrate stability? Which reactions do we expect when submarine gas hydrate reservoirs destabilize? What role do benthic microorganisms play during the persistence and dissociation of submarine gas hydrates? We would like to encourage also scientists who study gas hydrates in submarine permafrost to submit an abstract to this session.