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Abstract

The element carbon forms the basic building block of all organic biomass on Earth. It consists of two stable isotopes with a mass of 12u (atomic mass unit) and 13u. Biological formation, degradation and alteration processes fractionate the carbon isotopes. Biological systems typically prefer the incorporation of 12C into their biomass and discriminate with regard to 13C. Thus, the compound-specific carbon isotope analysis on characteristic biomolecules for specific precursor organisms allows to assess biological sources and processes being involved in the biological cycling of carbon and to conclude on environmental and climatic conditions affecting these processes. Here two examples from the ongoing work at GFZ are presented showing the influence of geogenic processes on biological systems. This Geo-Bio-coupling is revealed by analyzing the carbon isotope composition of specific key components in the respective biological carbon system. Carbon sources and biological processes were discovered and the obtained results provide deep insights into the feedback of biological ecosystems to increased levels of greenhouse gas concentration in natural systems.