@article {Thresher2016260,
	title = {Scale dependence of environmental and physiological correlates of δ18O and δ13C in the magnesium calcite skeletons of bamboo corals (Gorgonacea; Isididae)},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {187},
	year = {2016},
	pages = {260 - 278},
	abstract = {Abstract We examine in detail δ18O and δ13C in the calcite internodes of bamboo corals as potential proxies of physiological and environmental variability, through (a) a {\textquotedblleft}core top{\textquotedblright} calibration that includes specimens from a wide range of habitats and environmental conditions and (b) a comparison of high resolution serial point analyses along radial growth axes of a sub-set of specimens with each other, with instrumental temperature and salinity records, with growth rates and with a nominal skeletal proxy for temperature (Mg/Ca) in the same specimens. At the whole-of-specimen level, δ18O and the intercept of the strong within-specimen regression of δ18O against δ13C correlates highly with ambient temperatures at slopes that are identical to those reported for other marine biogenic carbonates (-0.22 per {\textdegree}C). δ13C varies predominantly with apparent specimen-mean growth rate. It also correlates with the slope of the within-specimen covariance between δ18O and δ13C, which in turn is distributed bi-modally among specimens and linked to differences in apparent growth rates. Within-specimens, variability in δ13C, and to a lesser extent δ18O, correlates between specimens collected in the same region and differs between regions, implying an environmental effect, but the factors involved for either isotope ratio are unclear. Correlations between δ18O and temperature (and Mg/Ca) range from positive to negative among specimens and appear to vary over time even within specimens. The mismatch between the consistent temperature-dependence of δ18O at the whole-of-specimen level and the mixed relationship within-specimens can be reconciled by assuming an unknown temperature-dependent factor affecting δ18O during the growth of Isidid calcite. The contrast between the results of the {\textquotedblleft}core top{\textquotedblright} temperature calibration for δ18O, which are consistent with studies of other carbonates, and the apparently more complex suite of factors affecting both δ13C and δ18O within specimens strongly suggests that calibrations based on a {\textquotedblleft}core top{\textquotedblright} approach be applied cautiously to environmental reconstructions based on variations of a nominal proxy within specimens.},
	keywords = {Temperature},
	issn = {0016-7037},
	doi = {http://doi.org/10.1016/j.gca.2016.05.024},
	url = {http://www.sciencedirect.com/science/article/pii/S0016703716302678},
	author = {Ronald E. Thresher and Helen Neil}
}
