We are interested in cryptic biogeochemical processes, in other words, those that are easily overlooked by traditional analyses involving the quantification of reaction intermediates or end products over time. Steady-state concentrations of certain redox species may arise from the balance between continuous oxidation and reduction reactions, and although concentration changes cannot be measured, their rapid turnover can play a key role in the environment and sustain highly active and diverse microbial communities. Our group specializes in the application of interdisciplinary approaches – borrowing methods from the fields of biology, geology, and chemistry – to solve complex environmental questions related to biogeochemical cycling.
Here you will find our ongoing projects!
Open Master’s projects:
Mobilization of iron and metals in aquifers. Processes mediated by microorganisms largely control contaminant mobility in aquifers. In particular, microbial reduction of iron oxide remarkably contributes to mobilizing iron and other hazardous metals, e.g., chromium, arsenic, and uranium, often absorbed on iron oxide surfaces. The occurrence and the rate of microbial iron reduction are mostly determined by the availability of organic carbon and oxygen. This project intends to grow a well-known iron-reducing bacterium Shewanella oneidensis in the presence of variable concentrations of organic carbon and oxygen. Different conditions encountered in natural systems are simulated, from shallow-sandy to deep-clayish aquifers. The impact of the different conditions on microbial activity and iron mobilization will be assessed using colorimetric assays, mass spectrometry, Total Organic Carbon quantification, and optical microscopy. The results will allow for quantifying iron-oxide reduction rates mediated by microorganisms in different scenarios and estimating iron and other metal mobility using geochemical modeling approaches.
N2O production in lowland lakes. Nitrous oxide (N2O) is an ozone-depleting chemical and the third most important greenhouse gas (GHG) causing climate change, with 300 times greater global warming potential than CO2. The current contribution of freshwater lakes to N2O emissions is still debated. However, anthropogenic activities and the limited oxygen diffusion in waters are expected to boost N2O production in freshwaters. Therefore, identifying the emission and production of N2O in aquatic ecosystems is essential for predicting its impact on future global climate projections. In aquatic ecosystems, N2O production is thought to be essentially in sediment, with emissions to the atmosphere occurring during mixing events. However, how much water-column microbes also contribute to nitrogen fixation and cycling in lakes is often overlooked. Pelagic microbial communities might play a more important role than benthic microbes in N2O production and therefore the goal of this project is to determine 1.) the presence and magnitude of N2O in waters, 2) the identity of N2O producing microbes, and 3) the effect of environmental variables like temperature on N2O emissions in the waters of Lake Geneva. This project will combine techniques in field work, gas chromatography, molecular sequencing, and some physical modeling.
Evaluating greenhouse gas production by lichens. Lichens are a symbiosis between cyanobacteria or algae and fungi and can be considered pioneering organisms colonizing nutrient-poor environments by fixing nitrogen and carbon dioxide from the atmosphere and leaching trace elements from highly insoluble substrates. Cryptogamic covers (including mosses) together account for approximately 49 Tg N fixation and 3.9 Pg C uptake per year, contributing ~7% of the yearly net primary production (Elbert et al. 2012). High C and N turnover by lichen-associated microbial assemblages may also affect N2O and CH4 production. New findings suggest that methane and N2O can be produced under aerobic conditions via a variety of metabolic pathways (Bižić et al. 2020; Fabisik et al. 2023) and are confirmed by our preliminary data on several alpine lichen species. Nonetheless, very few studies have explicitly evaluated how microbial communities associated with lichens produce greenhouse gases (GHGs) thereby impacting global climate. The goals of this project are to quantify the potential for CH4 and N2O production across common Swiss macrolichen species determine the effects of three key environmental factors, notably substrate type, temperature, and nitrogen availability, on GHG production.
Open Bachelor’s projects: please inquire directly for any customized projects applying sediment geochemistry, water quality, or molecular microbiology…
- Testing the viability of Lake Geneva macrophytes for use as biochar