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Digging for Diatoms Discovering Past Climates What are diatoms? Diatoms are beautiful single-celled organisms that live in glass homes made of silica. Their shells consist of two valves that fit together like a shoebox

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digging for diatoms

Digging for Diatoms

Discovering Past Climates

what are diatoms
What are diatoms?
  • Diatoms are beautiful single-celled organisms that live in glass homes made of silica. Their shells consist of two valves that fit together like a shoebox
  • Although thousands of species exist, diatoms are usually divided in two groups: the pennates (pen-shaped) or the centric (rounded)
  • They are abundant in both fresh and salt waters and their remains are widely distributed in soils where they form deposits.

Wim van Egmond

pen shaped or rounded
Pen-shaped or Rounded?





© Canadian Museum of Nature

a diatom by any other name
A Diatom by Any Other Name…
  • There may be up to 100,000 different species of diatoms (15,000 have been identified so far).
  • Each species requires certain ecological conditions in order to survive
  • Genus Fragilaria thrives under colder and more nutrient poor environments, while many centrics prefer warmer and more nutrient-rich surrounding.
who touched the thermostat
Who Touched the Thermostat?
  • Because of their ecological eccentricities, and the fact that their glass shells remain long after they die, diatoms can provide scientists with a stunning insight into the environments and climates of the past!
  • By dating a soil sample and studying its diatom fossil content (number and type), we can estimate the climate of a given period.
the core of this experiment
The Core of This Experiment…
  • 485 cm sediment core
  • Bottom of lake JR01 on Boothia Peninsula, Nunavut Territory
  • Base of core dated to 6700 years b.p. using radiocarbon analysis
  • Middle Holocene
  • All of recorded human history

© Canadian Museum of Nature

where and how to core
Where and How to Core?


Boothia Peninsula

Lake JR01

coring a core
Coring a Core…

© Canadian Museum of Nature

the usual suspects
The Usual Suspects
  • Fragilaria sp.
  • Thrives in cold, nutirent-poor conditions
  • Can assume a variety of shapes but is always symmetrical
  • Usually no more than 15 microns in length
the usual suspects10
The Usual Suspects
  • Nitzschia sp.
  • Associated with warmer and more nutrient-rich environments
  • Completely symmetrical and smaller than other pennates.
the usual suspects11
The Usual Suspects
  • Cyclotella sp.
  • Thrives in more nutrient-rich environments
  • Good indicators of shorter ice covers and longer growing seasons
  • Perfectly round in shape
the usual suspects12
The Usual Suspects
  • Amphora sp.
  • Prefers colder water conditions and a less productive (nutrient-poor) environment
  • Partly symmetrical and shaped like a half-moon with both ends pinched.
  • Sometimes confused with Cymbella which has more striae.

More diverse and abundant =


Less diverse and scarcer =