Assoc. Prof. Dr. David Andrew Fike 

Local Controls on Sedimentary Microbial Activity and Biogeochemical Records

Geochemical records preserved within marine sediments are often used to investigate modern biogeochemical cycling and reconstruct how it has evolved over Earth history. However, recent work has shown that these geochemical records can reflect local conditions of the environments in which they formed (such as the sediment accumulation rate or amount of biomass in the sediments) – rather than the global biogeochemical cycles that they have historically been thought to represent. This distinction is critical when trying to reconstruct the long-term evolution of Earth’s surface environment. During my HWK Fellowship, I will work with Dr. Thorsten Dittmar (Oldenburg) to investigate how these local parameters impact microbial activity in sediments and influence the preservation and chemical form of sedimentary organic matter via modulation of microbial sulfate reduction. This work will take advantage of Dr. Dittmar’s unique expertise in Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to characterize the chemical structure of dissolved organic compounds in sedimentary samples from a range of depositional conditions. The results will provide new insights into the controls on organic matter preservation in marine sediments. I will also leverage expertise at the MPI/Marum to write a synthesis review of sulfur biogeochemical cycling, integrating traditional bulk and micro-scale approaches to create a new framework in which to reinterpret existing data.