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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 l.jpg

Digging for Diatoms

Discovering Past Climates


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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


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Pen-shaped or Rounded?

Centric

Pennate

Cyclotella

Nitzschia

© Canadian Museum of Nature


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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.


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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.


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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


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Where and How to Core?

Iqaluit

Boothia Peninsula

Lake JR01


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Coring a Core…

© Canadian Museum of Nature


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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


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The Usual Suspects

  • Nitzschia sp.

  • Associated with warmer and more nutrient-rich environments

  • Completely symmetrical and smaller than other pennates.


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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


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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.


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Remember

More diverse and abundant =

Warmer

Less diverse and scarcer =

Colder


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Early to Middle Holocene (≈6700 years ago)


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Neoglacial (≈3300 years ago)


Medieval warm period 855 years ago l.jpg
Medieval Warm Period(≈855 years ago)


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Little Ice Age(≈380 years ago)


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Recently…(≈45 years ago)



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