Baltic Sea mixing experiment

In coastal and marginal seas with stable stratification and reduced water exchange, hypoxic deep-water conditions are a frequently observed phenomenon. The so-called redoxcline, developing under such conditions at the top of the anoxic layer, is characterized by strong biogeochemical gradients, which are the location of some important microbially mediated element transformations. Here, our project hypothesis is that the rapid and intermittent modification of the local biogeochemical and microbiological conditions associated with lateral intrusions, in particular due to turbulent mixing between intrusions and ambient waters, constitutes an essential component of the redoxcline system. In order to understand how microbial processes are influences by mixing between intrusions and ambient waters we have artificially mixed water bodies from the suboxic and anoxic zone of the Central Baltic Sea in a microcosm experiment. We have sampled the water bodies before and after mixing at several time points for metatranscriptome analyses. Additionally also samples for metagenome sequencing were prepared from the original unmixed water bodies.