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