A cruise with the F.S. Meteor into the Cariaco Basin is scheduled for July 2017 with the goal to study the interactions between microbial communities, biogeochemical processes and physical forcing mechanisms. In the areas with suboxic and anoxic bottom water, it is planned to measure important biogeochemical transformations and to identify key groups of microbial organisms within the N-, S-, P- and trace metal cycles along transects, covering both the pelagic redoxcline as well as the sediments. Combined physical, chemical and microbiological measurements in the water column will reveal insights into the impact of lat­eral water intrusions and small-scale turbulence on microbial activities and element trans­formations rates. In the sediments, biogeochemical transformations and distribution of sedi­ment bacteria will be examined with regard to oxygen supply. Studies on the particle flux will link the pelagic and the benthic process studies. These studies will yield a more comprehen­sive general understanding of the interactions between physical and biogeochemical pro­cesses in oxygen deficient marginal seas.