Re: vital effect and genetics

[Stephen Schellenberg <schellen@xxxxxxxxxxxxx>]

In addition to the comments by Roopnarin and Bengtson, you should also 
consider the effect of kinetics (i.e., disequalibrium precipitation) as 
distinct from "vital effects", which may be attributable to symbiotic 
energy cycling, etc. For an elegant study that deconvolves kinetic and 
"vital" effects in zooxanthellate scleractinians, check out:

McConnaughey, T., 1989, 13C and 18O isotopic disequilibrium in 
biological carbonates: I. patterns, Geochimica et Cosmochimica Acta, 53, 
pp. 151-162.

McConnaughey, T., 1989, 13C and 18O isotopic disequilibrium in 
biological carbonates: II. in vitro simulation of kinetic isotope 
effects, Geochimica et Cosmochimica Acta, 53, pp. 163-171.

Other factors to consider: 

If infaunal benthic forams, to what sediment depth may a given species 
dwell and to what degree do individuals shift depth over 
ontogeny/biomineralization? Stable istope values (particulary carbon) may 
strongly vary with little depth change near the sediment-water interface.

If planktonic forams, consider the degree of seasonality in surface 
waters, timing/duration of reproduction/biomineralization patterns, etc.

Your idea remains an interesting angle, keep paleonet posted! 

Stephen Schellenberg
Department of Earth Sciences
University of Southern California
Los Angeles, CA 90089-0740