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Systematics of

O and H isotopes in

Animals

Presentation modified by Nadine

Quintana Krupinski

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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)

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Oxygen in animals

18O measured in tissues (body water,

hair) and tooth enamel (bone not

generally used)

Hair is isotopically offset from bodywater18O (hair is more positive)

Food effect

Enamel and bone have a constantoffset from body water18O

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Major O FluxesIN

Drinking and food water (not fractionatedduring uptake)

Atmosphere O2 Food solids

OUT

Respired CO2 (fractionated) Water in urine and feces

Water lost in exhalation, sweat, evaporation(fractionated)

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18O in bioapatite

Measured from PO4 and CO3 in bioapatiteand CO3 in carbonate (bone)

Apatite: Ca5

(PO4

)3

(OH, F, Cl)

CO3 can substitute for PO4 or for OH (also in otherplaces)

O in PO4 and CO3 rapidly equilibrates withbody water O

Either PO4 or CO3 is selected for analysis,depending on the diagenetic history of thebioapatite

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Apatite 18

O vital effects

18OApatite depends on the temperature andfluid composition (in 18O) at which the

biomineral precipitates. For homeotherms (mammals, birds), assume

constant body temp. and derive info aboutthe animals 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. PO4and CO3 (~8)

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Box model for animals

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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

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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)

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18O in hair

Hair (keratin) 18O is related to gut

water18O (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

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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 18

O values (Kohn & Cerling):

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Rats with a change in

drinking water18

O EnamelBody water

Hair

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Geographic patterns in

human hair18O

Ehleringer et al. 2008

Above: Geographic InformationSystem-generated maps of thepredicted average 18O of human

scalp hair across the continental

United States.

Tap water18O varies

Diet constant: continentalsupermarket diet w/ 18O 26

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Hydrogen in animals D measured in tissues (hair, feathers,

chitin), body water, breath, tooth

enamel or bone collagen

Hair is isotopically offset from bodywaterD

Food effect removed in these studies

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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)

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D in tissues and body water Hair follicle D is a mix of blood water and

food waterD:

Fraction of H atoms from food:

Body waterD:

Equations from Ehleringer et al. 2008

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Rats with a change in

drinking waterD

Body water Hair

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Geographic patterns in

human hairD

Ehleringer et al. 2008

Above: Geographic Information System-

generated maps of the predictedaverage D of human scalp hair across

the continental United States.

Tap waterD varies

Diet constant: continentalsupermarket diet w/ Dd 115

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Extra slides

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Changes in hair18O, D with

migration

Ehleringer et al. 2008