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Environmental and climatic controls on the carbon and oxygen isotope compositions of living and fossil ostracods from Lake Geneva

English title Environmental and climatic controls on the carbon and oxygen isotope compositions of living and fossil ostracods from Lake Geneva
Applicant Vennemann Torsten
Number 107958
Funding scheme Project funding (Div. I-III)
Research institution Institut de Minéralogie et Géochimie Université de Lausanne
Institution of higher education University of Lausanne - LA
Main discipline Geochemistry
Start/End 01.04.2005 - 31.03.2008
Approved amount 171'562.00
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Keywords (11)

Stable Isotopes; Ostracods; Paleoclimatology; Paleoenvironment; Paleoecology; Lake Geneva; geochemistry; isotope; carbon; oxygen; ecology

Lay Summary (English)

Lead
Lay summary
The stable oxygen and carbon isotope as well as trace element composition of living ostracods as well as their valves from sediment cores of Lake Geneva are being investigated at five different sites and water depths, together with the chemical and isotopic composition of the water column and the sediment pore fluids. A complete database of the main environmental parameters has been obtained during the last three years, including seasonal variations of pH, water temperature, chemistry and isotopic composition, current regime, pore water chemistry, and processes affecting the contents and isotopic composition of dissolved inorganic carbon. The ecology of the ostracods has also been studied and a complete database for each species concerning the relative abundance, bathymetric preferences, life cycle, microhabitat and ontogeny is available. This information, combined with the trace element and isotopic composition of ostracod valves allows for an evaluation of past environmental conditions of valve formation. For some species, water temperature was found to have the predominant effect on ostracod size; thus, morphometry may be used as paleothermometer. The oxygen isotope composition of ostracods does not appear to be in equilibrium with that of the water even though it reflects the O-isotope composition of the water and the temperature via a species-specific fractionation. The fractionation is dependant on the water chemistry, more precisely on the water hardness, and may vary from one location to the other. Good relationships between water temperature and Mg/Ca and Sr/Ca ratios were found for certain species. Yet, it is not clear if this correlation depends only on the water temperature or on variations of these ratios in water, which may themselves vary because of the temperature and primary productivity dependant precipitation of calcite in the water column. The modern system can now be used as a "natural experimental system" to help interpret past climatic-environmental changes from sediment cores going back in time. The outcome of the natural experiments will help to determine rate and time of growth as well as species-specific fractionation effects under well-constrained conditions adding critical information to the existing data base on the selected species. Because of Lake Geneva’s geographic position, relatively large size and hence long residence time of the water, its restricted and well-characterized catchment area, and the abundance of ostracods, this lake is well suited for this type of paleoenvironmental study. The climatic evolution of this central European site can then be compared in detail with other sites analyzed within central Europe and with the marine sites used as global records of climate change in order to evaluate regional changes in climate in the light of the global changes experienced.
Direct link to Lay Summary Last update: 21.02.2013

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Number Title Start Funding scheme
119935 Environmental and climatic controls on the carbon and oxygen isotope compositions of living and fossil ostracods from Lake Geneva 01.04.2008 Project funding (Div. I-III)

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