Sebastiaan VAN DE VELDE
University of California, Riverside
Measurement of microniches in marine sediment environment (Master thesis)
My first encounter with research was during my master thesis project. During this year I tried to develop a reliable method to detect microniches in marine sediments. Microniches being small (<1mm) structures where elements like sulfide, iron ... are found in higher concentrations as the immediate environment. Together with my promotors (Yue Gao and Willy Baeyens) I managed to use Diffusive Gradients in Thin Films (DGT) in combination with Laser Ablation Inductively Couple Plasma Mass Spectrometry to simultaneously detect sulfide and trace metal hotspots, leading to a publication in TrAC (Gao et al., 2015).
Electricity in the Seafloor (PhD project)
After my master thesis, I immediately continued with a (FWO funded) PhD project under the guidance of Filip Meysman and Yue Gao. This thesis focuses on the effect of cable bacteria on geochemical redox cycling in marine sediments. These bacteria form long cables (hence the name) up to 7cm in the upper layers of the sediment, and transport electrons from the deeper, sulfide rich layers to the upper, oxygen rich zone. This electron transport (i.e. electrical current) turns the whole seafloor in a battery and has a major impact on the geochemistry.
Impact of electrogenic sulfur oxidation on trace metal cycling in coastal sediments.
Cable bacteria perform electrogenic sulphur oxidation, whereby electrical currents over centimeter-scale distances couple the reduction of oxygen at the sediment-water interface to the oxidation of sulphur in the deeper sediment. This generates strong pH gradients in the pore water, which affects acid-sensitive minerals like iron sulphides and calcium carbonates. Cable bacteria are being discovered globally, but it is still largely unknown how this process affects sedimentary geochemistry. My project focusses on the geochemical implications for iron, sulphur and trace metal cycling in marine sediments.
Belgian Coastal Zone (North Sea, Belgium), Lake Grevelingen (North Sea, The Netherlands), East Gotland Basin (Baltic Sea, Sweden), Blakeney salt marshes (North Sea, United Kingdom)
early diagenesis, biogeochemical cycling, iron, sulphur, trace metals