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Presentation about my PhD research, given at the Australian National University in May 2007.

Presentation about my PhD research, given at the Australian National University in May 2007.

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  • 1. The chemistry of freshwater mussels as a proxy for late Holocene river conditions Emma Versteegh Simon Troelstra Hubert Vonhof
  • 2. VU University Amsterdam: Department of Paleoclimatology & Geomorphology
    • Marine
      • Foraminifera (e.g. single specimens, seasonality)
      • Coccoliths (single species)
      • Molluscs (seasonality, e.g. ENSO variability)
      • Corals
      • Sediments (end-member modelling)
    • Terrestrial
      • Speleothems
      • Molluscs (seasonality, e.g. NAO variability)
      • Palynology
      • Sediments (end-member modelling)
  • 3. Outline of this talk
    • Aim
    • Background
    • Setup of the project
    • Methods
    • Results
    • Conclusions
    • Future work
  • 4. Aim
    • Understanding shell chemistry
    • Developing a new proxy for river discharge, flood and drought frequencies
    • Reconstructing late Holocene (5000 BP – 500 BP) river conditions
  • 5. Freshwater mussels
    • Common
    • Archaeological finds
    • Museum collections
    • Seasonal growth increments
    • Precipitate  18 O in shell carbonate;  18 O shell depends on:
      • T
      •  18 O water
    • Record trace element concentrations in shell carbonate
    • Species: Unio crassus , U. pictorum , U. tumidus
  • 6. Stable oxygen isotopes
  • 7. Rivers Rhine and Meuse
  • 8.  18 O Rhine and Meuse
  • 9. Setup of the project
    • Monitoring experiment
    • 20 th century shells
    • Late Holocene shells
  • 10. Methods
    • Microsampling
      • Merchantek Micromill
    • Stable isotopes
      • Finnigan MAT 252
      • Finnigan Delta
    • Trace elements
      • ICP-OES
      • LA-ICPMS
  • 11. Monitoring experiment
    • Cages with living mussels in fish ladders
    • - Hagestein (Lek)
    • - Lith (Meuse)
  • 12. 20 th century shells
    • Rivers:
    • Meuse
    • Rhine / Waal / Lek
    • Collection dates:
    • 1918
    • 1977 - 1978
    • 1998 - 2005
  • 13.  
  • 14. Late Holocene shells
  • 15. Research questions
    • Do growth lines in the shell correspond to yearly winter growth stops?
    • Does  18 O shell correspond to predicted  18 O shell ?
    • Does the mussel incorporate trace elements in equilibrium with ambient water?
  • 16. Results: 20 th century shells
  • 17.  
  • 18.  
  • 19.  
  • 20. Predicted  18 O
  • 21. Predicted  18 O shell vs.  18 O shell  18 O shell corresponds well with predicted values   18 O shell is useful proxy
  • 22.
    • Growth stop occurs at 11.9°C
    Predicted  18 O shell vs.  18 O shell
  • 23. Calculated  18 O water vs. monthly mean  18 O water
  • 24. Trace elements
  • 25. Trace elements Winter Winter Winter Winter
  • 26. Results: Late-Holocene shells
  • 27. Conclusions
    • In winter no carbonate is precipitated
    • Growth lines usually correspond to winter growth stops, but not always!
    •  18 O shell corresponds well with predicted values
    •   18 O shell is useful proxy
    • Several trace elements show seasonal patterns
    • It is not yet clear if this is due to:
      • Water composition
      • Temperature
      • Biological fractionation (vital effects)
    • Ca. 4500y old shells show seasonal stable isotope patterns similar to modern shells
      •  no diagenesis (?)
  • 28. Future work
    • Stable isotope analyses of monitoring shells
    • More stable isotope analyses of late Holocene shells
    • Trace element analyses (LA-ICPMS) on monitoring, 20 th century and Holocene shells
  • 29. What to do with LA-ICPMS?
    • Resolve slowly-growing parts of shells
    • Establish relationship between trace element composition of water and shell
    • Resolve growth lines of long-living freshwater pearly mussel Margaritifera margaritifera (>150y old)
    • North Atlantic Oscillation variability
  • 30. Preliminary results LA-ICPMS
  • 31. Preliminary results LA-ICPMS
  • 32. Polymesoda
  • 33.
    • Thank you!