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Projects |
2009 - Present |
Projects |
Methane (CH4), a very potent green house gas, is generated in seabed sediments. Because of high deposition of organic matter, continental margins, estuaries, harbors and river deltas are hotspots for methane production. The amount of CH4 produced in the sediments depends on the amount and quality of organic carbon buried in the sediment. In marine sediments, where sulfate concentrations are high most of the buried organic carbon is degraded by anaerobic sulfate reduction. As sulfate becomes consumed further down in the sediment, carbon mineralization is taken over by methanogenesis. In the absence of oxidants the produced CH4 accumulates and may move upwards through the sediment via diffusion or as gas phase through cracks in the sediment. Accumulation of shallow gas in continental shelves is a widespread phenomenon and is usually found in rapidly accumulating and thick sediments. Investigations in Aarhus Bay and other areas showed that gas only accumulated where the organic- rich Holocene mud exceeded 4-5 m in thickness. However, until today, it is unclear how and why the CH4 is accumulating in areas with thick Holocene mud layers, but not in layers < 4-5 m thick. In a second project I am investigating the effect of salinity and the origin and quality of organic carbon on CH4 fluxes in the sediment of the Gdansk Bay. Both these projects are embedded in the EU founded project BALTIC GAS. 2004 - 2008 PhD Project The aim of this dissertation was to assess the effects of simulated global warming and N enrichment on biogeochemical processes involved in the carbon cycle and on microbial communities in a freshwater wetland. Global warming and sustained N deposition were simulated in a mesocosm field experiment by raising average water temperature to a target of 4 ºC above ambient and periodically fertilizing mesocosms with a solution of Ca(NO3)2 to a target concentration 5 times above ambient. The responses measured included methane (CH4) emission (ebullition and diffusive flux), litter decomposition, and a range of parameters characterizing litter-associated microbial communities. We performed the experiments in a highly productive littoral stand of common reed, Phragmites australis, in Central Switzerland, located on the eastern shore of Lake Hallwil. 1. Experimentally simulated global warming and nitrogen enrichment effects on methane emissions in a marsh (more details....) 2. Experimentally simulated global warming and nitrogen enrichment effects on microbial litter decomposers in a marsh (more details....) 3. Responses of litter decomposition and associated microbial activity to simulated global warming and nitrogen enrichment: disentangling direct environmental and litter quality effects (more details....) |
What controls methane fluxes in coastal sediments? |
Sunset over the Baltic Sea on RV Aranda. |
Installing the mesocosms in the reedstand of Lake Hallwil. |