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Hi All...

In agreement with Gabe, food is a very important source of oxygen and  
there is a large (~+28 per mil) fractionation between leaf water  
oxygen and cellulose oxygen... Oxygen isotope values of non-obligate  
drinkers, who get a larger proportion of their oxygen from cellulose  
and/or leaf water, would have higher values than animals who need to  
drink...

Hydrogen is a much less complicated story, with smaller  
fractionations... But I think those who utilize hydrogen in avian  
studies have to start measuring isotopic variation in food sources as  
well as the consumer... Are there any data on food web hydrogen  
isotopes values? Has anyone gone out and systematically collected and  
analyzed (for hydrogen) a terrestrial food web from primary producers  
to top consumers? I think there is a lot more variation at the local  
scale than people assume, and this is likely the most important  
contribution to the noise we deal with when trying to assign  
individual birds (or groups of birds) to specific geographic areas...  
I realize that by analyzing consumer tissues with intermediate  
turnover rates you can assume as certain degree of integration  
(especially when viewed from the population level), but among- 
individual variance among can have powerful ecological  
implications... The isotopic ecology community who utlizes hydrogen  
(80-90% of whom study birds) needs to better characterize isotopic  
variation in the things that birds are putting in their mouths... I  
think we will be surprised at the amount of hydrogen isotope  
variation we see at the local level...

Off on a tangent...

Seth
aka Wombat Boy







On Dec 14, 2007, at 2:26 PM, Bowen, Gabriel J wrote:

> Hi Harro,
>
> Food is an important source of H and O to the body water, as is  
> atmospheric O2 through metabolism.  In general, I would expect the  
> opposite of the pattern you describe below...body water d18O should  
> be relatively heavy due to metabolic (+23.5) and dietary (ca. +10  
> and greater) contributions, whereas the d2H should be not too  
> dissimilar from drinking water (plant and animal tissue d2H is only  
> moderately 2H-enriched relative to environmental water).
>
> There is a lot of published work on 18O in body water, for a good  
> example w/ some synthesis see Bryant and Froelich, GCA: 59,  
> 4523-4537, 1995.
>
> Podlesak and colleagues have also published some relevant data in  
> the latest issue of GCA: 72, 19-35, 2008.
>
> Best,
> Gabe Bowen
>
> -----Original Message-----
> From: Stable Isotope Geochemistry [mailto:[log in to unmask]]  
> On Behalf Of H.A.J. Meijer
> Sent: Friday, December 14, 2007 10:53 AM
> To: [log in to unmask]
> Subject: [ISOGEOCHEM] 2H and 18O values for "blood" water and body  
> tissue
>
> Dear colleagues,
>
> My estimate for the isotope values for blood (that is the water
> component) in humans and animals would be that it has to be pretty
> close to the local (drinking) water. It is possibly slightly enriched
> due to evaporation processes in the body as well as in the open water
> available in nature for animals to drink, but not by more than a few
> per mil.
> In the "bakground" samples we process for doubly labelled water
> studies, however, relatively high values for 2H occur regularly,
> sometimes higher than + 50 o/oo. 18O is always in the local natural
> range that I expect.
> Is this an artefact, i.e. contamination by memory effects in the lab,
> or in the field, or during sample storage (samples are being stored
> in flame-off capilaries)?. If so, why does it  never happen for 18O?
> Or is it real? We know that the hydrogen in body water interacts with
> H in tissue to some extent, but can tissue be that highly enriched in
> 2H? And if so, why is it so variable?
> Is there any experience with "blood water" isotopes in fields where
> people do not use enriched water as well, f.i. in forensics?
>
> Thanks on forehand for helping!
>
> best regards,
>
> Harro
> -- 
>
> Prof. dr. Harro A.J. Meijer
> Centrum voor IsotopenOnderzoek (CIO), Rijksuniversiteit Groningen
> Nijenborgh 4, 9747 AG  Groningen, Netherlands
> tel +31-50-3634760   fax +31-50-3634738
> http://www.rug.nl/cio

Seth Newsome, Ph.D.
Carnegie Institution of Washington
Geophysical Laboratory
5251 Broad Branch Road NW
Washington, DC 20015
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(202) 478-8987