VITAL EFFECTS IN ACROPORA CERVICORNIS CORALS: EVIDENCE FROM TRACE ELEMENTS AND STABLE ISOTOPES

Chemical fractionation of ambient conditions due to biological processes (i.e. ‘vital effects') has the potential to significantly skew interpretations and paleoenvironmental reconstructions from biogenic carbonates. Quantifying this effect in corals is especially important since trace elements and stable oxygen and carbon isotopic data from coral skeletons are often used as proxies for various paleoceanographic processes and paleoclimate phenomena. Here we offer evidence from statistical analysis of geochemical data from Acropora cervicornis, which shows that correlations between stable isotopes (δ¹⁸O and δ¹³C) and trace elements (Sr, Mg, Fe, Mn, and Ba) are stronger in lateral rather than axial corallites of this branching coral species. Weaker correlations between stable isotopic and trace element data in axial corallites may be the result of 1) rapid initial calcification associated with a carrier-mediated ion transport mechanism, and 2) geochemical blurring due to slow continuous secondary skeletonization. On the other hand, stronger correlations between stable isotopic and trace element data in the lateral corallites may be attributed to weaker carrier-mediated ion transport on a cellular level, which would allow for the incorporation of trace elements into the coral skeleton in near-ambient seawater concentrations. Lateral corallites of Acropora cervicornis appear to be less affected by ‘vital effects', whereas axial corallites are characterized by continuous geochemical overprinting during growth. Thus, lateral corallites of branching corals may be more useful for paleoclimate reconstructions.