Organische Geochemie

About

I am generally interested in the lipid biogeochemistry of prokaryotic and eukaryotic microorganisms and how they are involved in the cycling of nutrients on local to global scales with a focus on diazotrophic cyanobacteria. For this, I employ culture-dependent approaches to increase our knowledge on the lipid inventory of microbial organisms and study the effect of growth conditions on lipid distribution patterns on a cellular level. Information obtained from these culture studies is transferred to the geological record to reconstruct fossil ecosystems and their change over time. My research interests thus range from investigating microorganisms under controlled laboratory conditions to the study of modern marine, lacustrine and terrestrial microbial communities and their role in global biogeochemical cycles and the interaction between geo- and biosphere over geological time scales.

 

A major focus of my current research is cyanobacteria. These microorganisms play a fundamental role in the modern global carbon and nitrogen cycles and are invoked to have played an important role in sustaining the high productivity that lead to repeated deposition of organic-rich sediments during e.g. Cretaceous Oceanic Anoxic Events and the deposition of Pleistocene sapropels of the Mediterranean. Understanding how cyanobacterial activity lead to the deposition of such organic-rich deposits is a key interest of my research.

 

Heterocystous cyanobacteria are a subgroup of the cyanobacterial lineage and play an important role in the cycling of nitrogen in fresh- and brackish waters. Under nitrogen-limited conditions may form massive blooms, known as harmful cyanobacterial blooms (cyanoHABs). Climate warming may lead to a significant proliferation of cyanoHABs in the future but how climate warming will promote the frequency and intensity of cyanoHABs and determine the community composition is large unknown. To study these blooms in the past, I employ novel biological marker, so-called heterocyst glycolipids (HGs), for which I developed a rapid screening technique using high performance liquid chromatography coupled to tandem mass spectrometry. Previous culture experiments have shown that the relative abundance of HGs shows a strong positive correlated with water temperature and in form of the HDI26 allows reconstructing modern and past lake surface water temperatures. The HDI and other HG-based indices may therefore provide novel lipid paleothermometers to study continental climate change, for which other organic temperature proxies such as the TEX86 or UK37 are not or only to some extend applicable. Closing this