Sediment erosion and transport is critical to the ecological and commercial health of aquatic habitats from watershed to sea. There is now a consensus that microorganisms inhabiting the system mediate the erosive response of natural sediments ('ecosystem engineers') along with physicochemical properties. The biological mechanism is through secretion of a microbial organic glue (EPS: extracellular polymeric substances) that enhances binding forces between sediment grains to impact sediment stability and post-entrainment flocculation. The proposed work will elucidate the functional capability of heterotrophic bacteria, cyanobacteria and eukaryotic microalgae for mediating freshwater sediments to influence sediment erosion and transport. The potential and relevance of natural biofilms to provide this important 'ecosystem service' will be investigated for different niches in a freshwater habitat. Thereby, variations of the EPS 'quality' and 'quantity' to influence cohesion within sediments and flocs will be related to shifts in biofilm composition, sediment characteristics (e.g. organic background) and varying abiotic conditions (e.g. light, hydrodynamic regime) in the water body. Thus, the proposed interdisciplinary work will contribute to a conceptual understanding of microbial sediment engineering that represents an important ecosystem function in freshwater habitats. The research has wide implications for the water framework directive and sediment management strategies.
In einer netzwerkfaehigen, benutzerfreundlichen, menuegesteuerten Datenbank, die auf einem Personalcomputer (Betriebssystem MS-DOS) lauffaehig ist, werden Informationen zu Betriebsschutz (Arbeitssicherheit), Umweltschutz (einschl Abfallentsorgung) sowie Transport, Lagerung und Erste Hilfe gespeichert. Insbesondere werden Stoffeigenschaften, Sicherheitsmassnahmen fuer den Umgang und gesetzlich vorgeschriebene Kennzeichnungen angegeben. Diese Angaben beziehen sich zum einen auf reine Chemikalien und zum anderen auf Versorgungsartikel (Produkte, Zubereitungen) der Bundeswehr (zB Reinigungsmittel, Klebstoffe, Lacke etc ). Die Liste der Gefahrstoffe ermoeglicht es jeder Dienststelle, Betriebsanweisungen nach Paragraph 20 der Gefahrstoffverordnung (GefStoffV) zu erstellen. Die GefStoffLBw enthaelt derzeit Daten zu ca 900 reinen Stoffen und ca 2000 Versorgungsartikeln.
Formation and stability of soil micro-aggregates depend on the forces which are acting between the individual building blocks and in consequence on type, size and properties of the respective adjacent surfaces. While the interaction forces are the result of the superposition of short-range chemical forces and long-range van-der-Waals, electrostatic, magnetic dipole and capillary forces, the total contact surface is a function of the size, primary shape, roughness and larger-scale irregularities. By employ-ing atomic force microscopy (AFM), we will explore the role of topography, adhesion, elasticity and hardness for the formation of soil micro-aggregates and their stability against external stress. Special consideration will be put on the role of extracellular polymeric substances as glue between mineral particles and as a substance causing significant surface alteration. The objectives are to (i) identify and quantify the surface properties which control the stability of aggregates, (ii) to explain their for-mation and stability by the analysis of the interaction forces and contacting surface topography, and (iii) to link these results to the chemical information obtained by the bundle partners. Due to the spatial resolution available by AFM, we will provide information on the nano- to the (sub-)micron scale on tip-surface interactions as well as 'chemical' forces employing functionalized tips. Our mapping strategy is based on a hierarchic image acquisition approach which comprises the analysis of regions-of-interest of progressively smaller scales. Using classical and spatial statistics, the surface properties will be evaluated and the spatial patterns will be achieved. Spatial correlation will be used to match the AFM data with the chemical data obtained by the consortium. Upscaling is intended based on mathe-matical coarse graining approaches.