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OUTLINE
• Basic diatom biology and methods
• Local example
• Lake El’gygytgyn diatom record
What are Diatoms?
• Unicellular (sometimes forming colonies)
• Siliceous cell walls
• Algae – Class Bacillariophyceae
valve
frustule (complete cell)
Pennate
Centric
monoraphid
araphid
biraphid
Where do they live?
plankton periphyton (benthos)
How do they reproduce?
10μ
Pliocaenicus
Cyclotella
Methods
•Sediment processing
•Light microscopy •Electron microscopy
Diatoms are sensitive to:
•salinity
•ice cover
•pH
•depth
•nutrients
•temperature
Linking diatoms to paleoclimate?
Transfer Function Approach:
Modern Environmental Conditions
Modern DiatomAssemblage+
Transfer Function Approach:
Modern Environmental Conditions
Modern DiatomAssemblage
Species Optima
Core Assemblage
Environmental Reconstruction
+
Summary
•broad distribution, preservation
•diverse and sensitive(+)
•not observed to be temperature sensitive
•taxonomy complex
•taphonomy
(-)
10μ
Unique Diatoms
PlanktonSize
General Patterns
OlderTaxonomic
Shifts
2.94 Ma – lacks ornamentation; valve face fultoportulae near center
3.09 Ma – ring of valve face fultoportulae near margin disrupt areolae pattern
3.21 Ma – ornamentation on valve face
General Patterns
1.103 Ma
1.095 Ma
1.071 Ma
1.060 Ma
1.057 Ma