Das Projekt "Binnenseesedimente als indirekte Archive fuer die Rekonstruktion der Umweltdynamik in Raum und Zeit: Eichung und quantitative Rekonstruktion in den Alpen (AQUAREAL)" wird vom Umweltbundesamt gefördert und von Universität Bern, Systematisch-Geobotanisches Institut durchgeführt. In a first phase (1993-1995) the basic scientific tools are built up and developed that will enable statistically reliable quantification of palaeo proxy-data in terms of past environment. This involves the development of modern transfer-functions and the calibration of proxy-data time-series. The project uses two independent approaches: a) establishment of mathematical/statistical relationships between different biological organisms and environmental variables, i.e. calibration or transfer functions by means of modern surface sediment samples. Surface samples from 68 lakes in altitudes between 300 and 2400 m a.s.l. have been sampled and the analyses of the different microfossils groups is in progress. b) cross-correlation of sub-recent varve parameters in Baldeggersee with instrumental meteorological records for the period of 1901-1993. Little is known about the relationship between ecological and climatic parameters influencing varve formation in lakes. It is therefore essential to define potentially sensitive climatic parameters in the varves as well as to separate statistically the nutrient impact of the lake from the climate signal. Measurements of sediment accumulation during the summer portion of the annual layer may provide a direct or indirect measure of climatic events that affect the biological growing season. The proposed project aims at reconstructing the past dynamics of terrestrial and aquatic ecosystems. In a first phase (1993-1995) the basic scientific tools will be built up and developed that will enable statistically reliable quantification of palaeo proxy-data in terms of past environment. This quantitative environmental reconstruction involves the development of modern transfer-functions and the calibration of proxy-data time-series. The proposed project has two independent parts: a) calibration or transfer functions for climate (pollen, Chironomids) and/or nutrients (Cladocera, diatoms) by means of 50-100 modern surface sediment samples. b) cross-correlation of sub-recent varve parameters in Swiss Plateau lakes with instrumental meteorological records and tree-ring time-series. In a second phase (1996-2000) the results of these two approaches will be applied to long proxy-data records along a transect across the Alps in order to reconstruct past environments and to assess natural variability, as well as to identify phases and amplitudes of the driving parameters (e.g. climate, human impact). Leading Questions: What are the natural variability and long-term dynamics of ecosystems and climate? What are the amplitudes of past rates of change? How long are the response times of ecosystems to perturbations? How are environmental signals reflected in lacustrine sediments?
Das Projekt "Mineralogische Umwandlung amorpher Eisensulfide in See-sedimente: ein potenzieller Stellvertreter-Indikator fuer den Klimawandel" wird vom Umweltbundesamt gefördert und von Eidgenössische Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz, Wasserforschungs-Institut, Forschungszentrum für Limnologie durchgeführt. Precipitation of iron sulfides in sediments of deep lakes is linked to lake productivity and deep-water mixing. The concentration of iron sulfides in lake sediments may therefore contain information on the intensity of deep-water mixing, which is governed by climate variables such as wind speed and temperature. It is the goal of this project to make the geochemical information stored in iron sulfides in sediments more accessible for the reconstruction of past environmental conditions. Through an international collaboration with a group at the University of Grenoble the project will initiate a fundamental study of mineralogical transformations of iron sulfides in sediments. Synchrotron-based X-ray spectroscopy (EXAFS) offers new possibilities to obtain structural information from poorly cristallized samples. The method will be combined with in-situ analytical techniques to determine the sulfide record in different sedimentary environments (Lakes Baldegg and Lugano in Switzerland , Lake Baikal in Siberia and the Black Sea continental shelf). Leading Questions: The proposed study is focused on the following research goals: - To determine the local structure of amorphous iron sulfides derived from the reduction of different iron oxides and hydroxides by sulfide; - the apply this knowledge to the study of amorphous iron sulfides which prevail in lake sediments and to the crystal chemistry of intimately associated trace/minor elements; - to calibrate iron sulfides in sediments as a redox indicator of deep-water anoxia; - to apply this indicator for the reconstruction of aspects of continental climate variability in the last 10'000 years.