A Pilot Study on Zinc Isotopic Compositions in Shallow‐Water Coral Skeletons

Abstract

Abstract 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 (δ66Zn) in coral skeletons may possibly serve as potential tracers for climate and environmental changes. In this study, we first reported the δ66Zn in shallow‐water coral skeletons by investigating with monthly resolution δ66Zn values in the skeleton of a modern Porites coral 10AR2 from the Great Barrier Reef of Australia, and the bulk skeletal δ66Zn values of several coral species from the Luhuitou Reef of Hainan Island in the northern South China Sea. Correlations between δ66Zn and other climate and environmental proxies (Sr/Ca, δ18O, and δ13C) 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 δ66Zn in coral skeletons are not significant. However, significant interspecific differences in the skeletal δ66Zn of corals growing under identical external environments may suggest the occurrence of biologically controlled δ66Zn fractionation during coral skeletons formation. In addition, the monthly δ66Zn in the 10AR2 coral skeleton roughly decreases with increasing temperature, which is in agreement with the recent finding that δ66Zn 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 δ66Zn as a climate and environmental proxy.

Keywords

• biological activity
• coral
• metal stable isotopes
• reactive oxygen species
• zinc isotope composition
• zooxanthellae