Das Projekt "Stimulation des mikrobiellen Stickstoffkreislaufs in aquatischen Sedimenten durch bioturbierende Makroinvertebraten" wird/wurde gefördert durch: Deutsche Forschungsgemeinschaft. Es wird/wurde ausgeführt durch: Max-Planck-Institut für marine Mikrobiologie.Bioturbierende Makroinvertebraten können den mikrobiellen Stickstoffkreislauf in aquatischen Sedimenten vermutlich erheblich stimulieren. Vor dem Hintergrund der hohen Belastung limnischer und brackiger Ökosysteme mit Nitrat und Ammonium kommt diesem Phänomen eine überaus wichtige ökosystemare Funktion als Senke für anorganische Stickstoffverbindungen zu. Der eigentliche Ort der stimulierten mikrobiellen Stoffumsetzungen, das Ökosystemkompartiment 'Wohnröhre' (gemeinsames Habitat von Makroinvertebraten und Mikroorganismen) ist in bisherigen Studien fast immer ausgeklammert worden, so dass keine Details über das quantitative Ausmaß der dort stattfindenden Prozesse bekannt sind. Daher soll die mikrobielle Lebensgemeinschaft der Wohnröhren bioturbierender Makroinvertebraten erstmals mit moderner Methodik auf (1) struktureller Ebene (Fluoreszuenzin-situ-Hybridisierung und Mikroautoradiografie) und (2) funktioneller Ebene (Mikrosensorentechnik) in Labor- und Freilandexperimenten untersucht werden.
Das Projekt "Oxygen depletion in a deep perialpine lake" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: School of Architecture, Civil and Environmental Engineering (ENAC), Environmental Engineering Institute (IIE), Laboratory of Physics of Aquatic Systems (APHYS).With this project we seek three years of support for a PhD study for quantifying the hypolimnetic oxygen (O2) depletion in Lake Geneva. This project builds on results from an earlier project 'Turbulence and Fluxes in Natural Waters (200020-120128)', where we have been able to measure O2 fluxes to the sediment by applying the microprofiling and eddy-correlation techniques and to relate these fluxes to the forcing by bottom boundary layer (BBL) currents. Additionally, it is an extension of the O2 depletion model recently proposed by the Eawag team (Müller et al 2012). In this new project, we will expand the approach of water-sediment interface fluxes via applications to much larger, more complex and more strongly forced hypolimnia than have been previously studied. The choice of the field-site Lake Geneva is due to (i) the occurrence of the highest hypolimnetic O2 depletion rates measured in Switzerland, (ii) the access to a rich data-set dating back to 1957, (iii) the proximity of the sites and the availability of infrastructure, (iv) the acquired knowledge on the physical forcing of Lake Geneva and (v) the intended build-up of collaboration with Institute FA Forel and CIPEL. Besides the resources requested from SNSF, this project will be additionally supported by (i) the external senior researchers involved, (ii) a post-doc / junior researcher and (iii) the utilization of newly-acquired equipment (microprofiler, ADCPs, CTD and TDO sensors; the latter two will be financed by the new Chair in 'Physics of Aquatic Systems' at EPFL. The aim of this project is to develop a data-based model for the quantification of hypolimnetic O2 depletion in large and complex hypolimnia derived from measured and modelled fluxes from the water column through the diffusive boundary layer (DBL) to the sediment (FW-S: mineralization of organic matter at the sediment surface) and measured fluxes of reduced substances (FS-W: oxygen-equivalents) from the sediment to the water. The hypolimetic O2 consumption is then estimated by FW-S + FS-W (g O2 m-2 d-1). Local budgets will be performed in the BBL and in lake-wide layers as a function of depth (z). After a conceptual test of this model was found to be successful for a large number of vertically integrated hypolimnia (Müller et al 2012), we intend to expand upon these results by studying time series of O2 depletion as a function of z. Based on data to be obtained during a two-year period of fieldwork in Lake Geneva, we will conduct process studies quantifying the two fluxes FW-S and FS-W and use the data to calibrate this oxygen model. The hydrodynamic modelling will be used to extrapolate the effect of wind for the last 55 years. We hypothesize that this oxygen model will allow interpreting O2 depletion in most of the large lakes on earth. usw.
Das Projekt "VAMP: Voltammetric Autonomous Measuring Probes for Trace Metals in the Water Column (500m, max depth) and at Water-Sediment Interfaces (6000m, max depth)" wird/wurde gefördert durch: Bundesamt für Bildung und Wissenschaft. Es wird/wurde ausgeführt durch: Universite de Neuchatel, Institut de Microtechnique.General Information: Two systems will be built for the autonomous measurement of trace metal concentrations in the water column and at the water-sediment interface. They are based on voltammetric microelectrode arrays, so the development of the sensor and voltammeter will be similar. VOLTAMMETRIC PROBE FOR THE WATER COLUMN, usable in the water column down to 500m, and controlled either by an operator from a ship, or automatically when attached to a buoy. The system will determine concentration profiles between 0-500 m, routinely in function of time and depth for 1-2 week and will be able to transmit the data to a land station by radio, telephone or satellite link. Cu(II), Pb(II), Cd(II) and Zn(II) will be measured with a sensitivity less than lOO pM. Extension to the analysis of Mn(II) and Fe(II) are foreseen. The probe will allow metal speciation: it determines specifically the 'truly dissolved' fraction of the trace metals (i.e. metal species smaller than ca 3 nm), directly in situ, without any sample handling thus minimizing methodological artefacts. Additional determination of the total metal concentration allows definition of the colloida) + particulate metal fraction by difference. Emphasis will be put on the development of cheap and reliable microelectrde arrays, uilt using new microtechnology. Recent developments in combining mercury film Ir based microelectrodes, in a special antifouling gel, providing high sensitivity and long-term stability of the sensor will be used. SEDIMENT-WATER INTERFACE MICROPROFILER, to determine concentration profiles of Pb(II), Cd(II) and Mn(II) (possibly also Cu(II) and Fe(II)) at the sediment-water interface, with submillimeter resolution. Microelectrode arrays with antifouling gel and with individually addressable electrodes will be used. The voltammetric probe and sensors will be placed on a lander already developed in the EUROMAR EU-408 BIMS project. Measurements down to 6000m will be stored or transmitted by cable (shallow depths) or by acoustic telemetry. The truly dissolved (i.e. the mobile) fraction of metals will be measured. A multipotentiostat and multiplexer will be combined to record the concentration profiles in 64 microelectrodes over a depth of 1 cm with a resolution of 100-200um without moving the electrode array in the sediment or a micromanipulator will be used to move the electrode array vertically. THE TWO SYSTEMS will be the first existing probe for the determination in situ of trace metal concentration in the water column and at the sediment -water interface.The tecniques to be used are feasible thanks to the well-integrated complementary expertise of the four partners. Leading Questions: in-situ measurements of tracer metals (mobile fraction) - in-situ profiling of tracer metals at the sediment/water interface.
