MSc Jörn Tonnius

Wide areas of the ocean bottom are only thinly covered by sediments. In these areas which are located mostly along the mid ocean ridges and at seamounts, basaltic oceanic crust can directly react with the oceanic water. Due to the high hydraulic conductivity of newly formed oceanic crust, this reaction zone extends down to several hundred meter below the seafloor. The oxidation of reduced elements in the crust (e.g. iron, manganese, sulfur) by electron acceptors in the oceanic water may be an important source of metabolic energy for chemolithotrophic microorganisms. During the last 15 years, there has been increasing evidence for the existence of an active microbial habitat on basaltic oceanic crust. The understanding of the involved processes, the methods employed by microorganisms to utilize these reactions and the scope of their influence on the marine geochemical cycle is still developing.
The main objective of my research is to study and quantify the influence of microbially catalysed weathering of basaltic glass on the dissolution rates and dissolution processes of the oceanic crust. To this end, collumn dissolution experiments were conducted to study the influence of different organic ligands, that play an important role in the microbial catalysis of analogous terrestrial weathering processes.

The aqueous concentration of dissolved hydrogen can be a used as an important indicator for the dominating redox-processes in aquifers. The aim of this master thesis was to establish the hydrogen detection method via a reduction gas detector (RGD2) at the geochemical laboratory of the university of Tübingen and to compare it with other assessment methods. The thesis was part of the BMBF fundig priority KORA. The method was tested with samples from an aquifer contamininated with chlorinated hydrocarbons in the city area of Frankenthal, germany.

• Changes in global geochemical cycles
• Deep biosphere and extreme habitats
• Geoengineering
• Marine Geochemistry
• The origin of life