NOAA/WDS Paleoclimatology - Arlington Reef, Great Barrier Reef, Porites sp. isotopes and trace elements 2006-2010 CE

The trace metal element zinc (Zn) participates in coral metabolic processes and therefore accumulates in their skeletons. These metabolic processes are largely controlled by the changes of environment in which they live, so Zn isotopic compositions (d66Zn) in coral skeletons may possibly serve as potential tracers for climate and environmental changes. In this study, we first reported the d66Zn in shallow-water coral skeletons by investigating with monthly resolution d66Zn values in the skeleton of a modern Porites coral 10AR2 from the Great Barrier Reef of Australia, and the bulk skeletal d66Zn values of several coral species from the Luhuitou Reef of Hainan Island in the northern South China Sea. Correlations between d66Zn and other climate and environmental proxies (Sr/Ca, d18O, and d13C) and instrumental environmental variables (sea surface temperature, river runoff, and chlorophyll a) are poor, suggesting that the effects of external environmental changes on monthly variations in d66Zn in coral skeletons are not significant. However, significant interspecific differences in the skeletal d66Zn of corals growing under identical external environments may suggest the occurrence of biologically controlled d66Zn fractionation during coral skeletons formation. In addition, the monthly d66Zn in the 10AR2 coral skeleton roughly decreases with increasing temperature, which is in agreement with the recent finding that d66Zn in coral tissues and zooxanthellae increases with increasing temperature and can serve as a proxy for thermal stress in corals. We thus suggest that the complicated coral internal biological processes hinder the use of skeletal d66Zn as a climate and environmental proxy.