Skeletal stable isotopic signatures of scleractinian reef corals have been widely acknowledged a sgood indicators of environmental conditions and are as such used in paleoclimate reconstruction. However, "vital effects" related to coral functioningn have been recognized to potentially distort climate reconstruction from biogenic carbonates precipitated by organisms such as corals.
A systematic comparison of the delta 18O climate proxy of short time-series of the massive coral Porites was conducted to unravel growth and species specific factors on the delta 18O climate signal. The replicate sampling of skeletal 18O time series showed no species specific isotope fractionation, but showed that non-environmentally induced isotope variation is mainly attributable to skeletal growth. When a correction factor for variation in skeletal growth was applied, all time -series depicted the 1982/83 El-Nino precursor of a severe drought at the collection site (Flores Sea, Indonesia) within the Western Pacific Warm Pool.
Further investigations on the Caribbean coral genus Madracis revealed that skeletal proxies may also be applied in questions related to physiological plasticity of scleractinian corals. Again growth related-isotope effects are a major player in skeletal isotope fractionation as inferred from fast and slow growing portions of a colony. The divergence of kinetic versus metabolic isotope fractionation turned out to be a useful tool in distinguishing coral species that are confined to a narrow depth distribution from coral species of a more generalist depth distribution pattern. The regression slope of isochronic skeletal delta 13C versus delta 18O skeletal surface samples increased with increasing water depth. The slope of delta 13C to 18O, given a representative range of surface samples of a colony has been sample, may thus provide a useful tool to reconstruct at what depth zooxanthellate corals grew. Using this relation from isochronic samples as an additional method may shed new light on topics such as sea-level changes and reef drowing.