diffusive-reactive model; lake sediments; organic matter mineralization; hypoxia; sediment porewater
Torres Natascha N., Chwalek Thomas, Droz-Georget Helen, Müller Beat, Brand Helmut, Hauser Peter C., Furrer Gerhard (2016), A novel method to quantify bioavailable elements and mobile ATP on rock surfaces and lichens, in Geosciences
, 2(3), 245-258.
Israel Joel Koenka, Nina Küng, Pavel Kuban, Thomas Chwalek, Gerhard Furrer, Bernhard Wehrli, Beat Müller, Peter C. Hauser (2016), Thermostatted dual-channel portable capillary electrophoresis instrument, in Electrophoresis
, 37, 2368-2375.
Jorge Saiz, Israel Joel Koenka, Carmen Garcia-Ruiz, Beat Müller, Thomas Chwalek, Peter C. Hauser (2015), Micro-injector for capillary electrophoresis, in Electrophoresis
, 36, 1941-1944.
Steinsberger Thomas, Schmid Martin, Wüest Alfred, Schwefel Robert, Wehrli Bernhard, Müller Beat, Organic carbon mass accumulation rate regulates the flux of reduced substances from the sediments of deep lakes, in Biogeosciences Discuss.
The major aim of this project is quantifying and understanding time and space dependent benthic diffusion of reduced substances (methane, ammonium, reduced iron and manganese, and sulphide) from lake sediments by extensive field observations, data analysis and the further development and application of a diffusive-reactive sediment model.Costly efforts on lake remediation such as advanced sewage treatment, ban of phosphate (P) in detergents, or reduction of diffuse nutrient loads from agriculture proved successful in preventing algal blooms and fish kills. Astonishingly the consumption of O2 in lake hypolimnia has remained tenaciously unchanged. A sound and generally applicable hypothesis relating areal hypolimnetic mineralization rate (AHM) to lake total P is not yet available. Recently Müller et al. [2012a] analysed a monitoring datasets from 20 Swiss lakes consisting of more than 50’000 O2 measurements, and related their hypolimnetic O2 consumption to only two processes: Mineralization of settled organic matter (OM) at the sediment surface, and oxidation of reduced substances diffusing from their sediment. Their model provides for the first time a conceptual interpretation of the areal hypolimnetic mineralization rate (AHM) of lakes developing an excessive O2 demand during summer stratification, and requires confirmation. Surprisingly, they reported very similar benthic fluxes of reduced substances in two lakes with distinctly different eutrophication histories. This observation asks for about a thorough assessment of the forces driving the fluxes of dissolved reduced substances. Obviously, porewater fluxes of reduced compounds are indicative for the sedimentary mineralization rate of OM, depending on the quality of OM and its exposure to various electron acceptors. However, spatial and temporal variation in OM degradation and porewater fluxes has not yet been systematically examined in lakes of different trophic states. This project intends to (i) determine benthic fluxes of reduced substances in two lakes of different trophic states (Lakes Aegeri and Baldegg) at various depths and seasons, and (ii) relate observed fluxes to the degradability of OM, burial rate, and stoichiometry of settling seston.An existing one-dimensional sediment model [Dittrich et al., 2009] taking into account benthic diffusive transport processes and biogeochemical reactions, will be adapted to elucidate the pathways of benthic OM degradation and the resulting benthic fluxes of reduced compounds as a function of temperature, benthic O2, NO3- and SO42- concentrations, as well as the sedimentation rate and quality of autochthonous as well as allochthonous inorganic and organic matter. In summary, this project will 1)provide results on depth dependent pathways and velocities of benthic OM cycling in two lakes of different trophic states,2)result in an improved qualitative and quantitative understanding of the benthic OM cycling in lakes, 3)lead to a conceptual dynamic model, simulating benthic oxygen consumption as a function of the actual and past inputs of OM and the availability of electron acceptors to the sediment, and hence 4)allow predicting the delayed decrease of benthic oxygen consumption after reduction of a lake’s primary production in aerated and non-aerated lakes.