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Systematics of O and H isotopes in Animals

Systematics of O and H isotopes in Animals. Presentation modified by Nadine Quintana Krupinski. Background.  18 O and  D values correlate strongly with local precipitation isotopic value Precip isotopic value varies w/ latitude and elevation

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Systematics of O and H isotopes in Animals

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  1. Systematics of O and H isotopes in Animals Presentation modified by Nadine Quintana Krupinski

  2. Background • 18O and D values correlate strongly with local precipitation isotopic value • Precip isotopic value varies w/ latitude and elevation • Local water isotopic value also affected by aridity (evaporation effect)

  3. Oxygen in animals • 18O measured in tissues (body water, hair) and tooth enamel (bone not generally used) • Hair is isotopically offset from body water 18O (hair is more positive) • Food effect • Enamel and bone have a constant offset from body water 18O

  4. Major O Fluxes IN • Drinking and food water (not fractionated during uptake) • Atmosphere O2 • Food solids OUT • Respired CO2 (fractionated) • Water in urine and feces • Water lost in exhalation, sweat, evaporation (fractionated)

  5. 18O in bioapatite • Measured from PO4 and CO3 in bioapatite and CO3 in carbonate (bone) • Apatite: Ca5(PO4)3(OH, F, Cl) • CO3 can substitute for PO4 or for OH (also in other places) • O in PO4 and CO3 rapidly equilibrates with body water O • Either PO4 or CO3 is selected for analysis, depending on the diagenetic history of the bioapatite

  6. Apatite 18O “vital” effects • 18OApatite depends on the temperature and fluid composition (in 18O) at which the biomineral precipitates. • For homeotherms (mammals, birds), assume constant body temp. and derive info about the animal’s environment. • For heterotherms, as temp. , bioapatite 18O  and carbonate 18O values . • In mammal apatite, constant offset btw. 18O of body water and PO4 (~18‰), btw. PO4 and CO3 (~8‰)

  7. Box model for animals

  8. Mass balance model 0.25 * [18OBW + 38.65] + 0.4 * [18OBW + 0] + 0.25 * [18OBW - 8.5] + 0.1 * [18OBW - 18] = 0.25 * 15 + 0.45 * [18OLW + 26.2 * (1 - h)] + 0.3 * 18OLW ) BW = body water LW = local water output input

  9. Models for O in body water • Portion of O from food, air (Ehleringer): • Isotopic ratio of body water (same eqn. for O&H, Podlesak): r = molar quantity of the input or output, R = ratio of the heavy isotope to the light isotope A = fractionation between body water and the output Alternatively, in  notation (Ehleringer)

  10. 18O in hair • Hair (keratin) 18O is related to gut water 18O (Ehleringer): OR, in R notation (same eqn. for O&H; Podlesak): Rfw = isotopic ratio of follicle water Rbw = isotopic ratio of body water Rfd = isotopic ratio of food

  11. 18O in tooth enamel • Tooth isotopic composition is derived from body water composition • Equilibrium fractionation yields a constant, temperature-dependent offset from body water • Podlesak use a model for continually growing teeth (e.g. rats) - large time-averaging of tooth isotopic signal • General tooth model using known input and output 18O values (Kohn & Cerling):

  12. Rats with a change in drinking water 18O Enamel Body water Hair

  13. Geographic patterns in human hair 18O • Tap water 18O varies • Diet constant: ‘‘continental supermarket’’ diet w/ 18O 26‰ Above: Geographic Information System-generated maps of the predicted average 18O of human scalp hair across the continental United States. Ehleringer et al. 2008

  14. Hydrogen in animals • D measured in tissues (hair, feathers, chitin), body water, breath, tooth enamel or bone collagen • Hair is isotopically offset from body water D • Food effect “removed” in these studies

  15. H sources and sinks • IN • Drinking water • Food water • Food (important! But may be controlled) • Small portion (10-15%) of H in synthesized hair exchanges w/ water • OUT • Urine and feces • Water lost in exhalation, sweat, evaporation (fractionated)

  16. D in tissues and body water • Hair follicle D is a mix of blood water and food water D: • Fraction of H atoms from food: • Body water D: Equations from Ehleringer et al. 2008

  17. Rats with a change in drinking water D Body water Hair

  18. Geographic patterns in human hair D • Tap water D varies • Diet constant: ‘‘continental supermarket’’ diet w/ Dd 115‰ Above: Geographic Information System-generated maps of the predicted average D of human scalp hair across the continental United States. Ehleringer et al. 2008

  19. Extra slides

  20. Changes in hair 18O, D with “migration” Ehleringer et al. 2008

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