Frontiers in Environmental Geoscience www.reading.ac.uk

Geography and Environmental Science

15 September 2011

Earthworm secreted calcite granules as a palaeoenvironmental proxyEmma Versteegh, Stuart Black, Mark Hodson

Earthworm secreted calcite granules as a palaeoenvironmental proxy

A new terrestrialpalaeoenvironment thermometer

• Many organisms

biomineralise

• Stable isotopes in

CaCO3 can record

environmental

variability

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Earthworm secreted calcite granules as a palaeoenvironmental proxy

Earthworm secretedcalcite (CaCO3) granules

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Earthworm secreted calcite granules as a palaeoenvironmental proxy

Aim

To construct a new terrestrial isotope – temperature curve

for application to earthworm secreted calcium

carbonate granules

→ Potential for granules in dating and palaeo-

environmental interpretation

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Earthworm secreted calcite granules as a palaeoenvironmental proxy

Oxygen isotopes (δ18O values)

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1000 ln αc-w = 18.03 (103T-1) - 32.42

δ18Owater & temperature →δ18Ocalcite

Kim & O’Neil (1997)

Earthworm secreted calcite granules as a palaeoenvironmental proxy 6

Earthworm secreted calcite granules as a palaeoenvironmental proxy 7

Earthworm secreted calcite granules as a palaeoenvironmental proxy 8

Earthworm secreted calcite granules as a palaeoenvironmental proxy 9

Earthworm secreted calcite granules as a palaeoenvironmental proxy

Aim

To construct a new terrestrial isotope – temperature curve

for application to earthworm secreted calcium

carbonate granules

• Potential for granules in dating and palaeo-

environmental interpretation

• How important are granules in locking up atmospheric

CO2?

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Earthworm secreted calcite granules as a palaeoenvironmental proxy

Carbon isotopes (δ13C values)

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• “You are what you

eat”

• Calcifying gland is a C

fixing organ

Briones et al. (2008)

Earthworm secreted calcite granules as a palaeoenvironmental proxy

Experiment 1

• 3 soils (C3 and C4

vegetation)

• 3 types of water (England,

Fiji, Norway)

• Constant temperature

(17 °C)

• 4 months

• 4 replicates

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Earthworm secreted calcite granules as a palaeoenvironmental proxy

Isotope analyses

Delta V advantage IRMS

• Flash EA 1112 HT

– δ2H and δ18O in water, soils,

manure, earthworms

• GasBench II

– δ13C and δ18O in granules,

water, DIC, CO2

SerCon– δ13C and δ15N in soils, manure,

DOC, DON

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Earthworm secreted calcite granules as a palaeoenvironmental proxy

Granule δ18O vs. δ13C

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adaptation to food~3 ‰

evaporation

Earthworm secreted calcite granules as a palaeoenvironmental proxy

δ13C in soils

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adaptation to food~3 ‰

Earthworm secreted calcite granules as a palaeoenvironmental proxy

δ13C in soils and granules

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Earthworm secreted calcite granules as a palaeoenvironmental proxy

Reconstructed δ18Owater

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Earthworm secreted calcite granules as a palaeoenvironmental proxy 18

Earthworm secreted calcite granules as a palaeoenvironmental proxy

Conclusions

• δ18O values of granules appear to

reflect ambient water

• δ13C values of granules adapt to

δ13C values of food (manure)

over < 1 month

• So far no evident link between

soil and granule δ13C values

→ more data needed

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Earthworm secreted calcite granules as a palaeoenvironmental proxy

Experiment 2

• 2 soils

• 3 types of water (England,

Fiji, Norway)

• 3 temperatures (10, 16,

21 °C)

• 3 weeks acclimatisation

• 1 month

• 6 replicates

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Earthworm secreted calcite granules as a palaeoenvironmental proxy

Future work

More analyses:

• Water δ13C, δ18O

• δ2H, δ15N

• More granules

Application on archaeological and geological samples

• Reconstruction of past temperatures

• Dating of samples by U/Th

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Earthworm secreted calcite granules as a palaeoenvironmental proxy 22

Thank you!

Questions?