Dear all

As part of a food web trophic structure study, I need to analyse
epiphytic crustose coralline (calcium carbonate containing) red
algae.  I am only interested in the organic, dietary nitrogen and
carbon - i.e. the N and C flowing through the trophic levels.  For N
I would use a non-acid-washed samples to eliminate the effect of the
treatment on changing the resulting delta15N value or the %N content.
However, how does one determine the 'true' (uneffected by acid
washing or the presence of carbonates) delta13C value for the algae,
keeping in mind that acid-washing is essential in order to eliminate
the non-dietary carbonates?

I would appreciate any suggestions from people who have analysed
coralline algae.

Best wishes,
Albertus J. Smit
AJ Smit
Botany Department
University of Western Australia
Nedlands
Western Australia
6907