Effects of microbial activity on marine carbonates
Calcium carbonates (CaCO32-‐) belong to the most common mineral groups within the marine realm. In this thesis interactions between marine microbes and carbonate stability are investigated in depth. Microbial biofilms are analyzed at high resolution regarding their functions in element and isotopic fractionation. In addition, calcite dissolution experiments were carried out to quantify the effect of aerobic methane oxidizing bacteria. Carbonate precipitation rates in marine sediments often serve as a fitting parameter for numerical modeling approaches to constrain. 45Ca and 14C-bicarbonate incubation experiments were carried out to quantify ongoing calcification in natural sediment slurries. During a research cruise rates of anaerobic methane oxidation and sulfate reduction were determined for the first time using radiotracers. The obtained rates were combined with carbonate isotopic signatures to elucidate local variations of fluid advection.