MEPS 245:93-100 (2002)  -  doi:10.3354/meps245093

ABSTRACT: Reef-building corals are very sensitive to changes in their environment and have been identified as potential accurate recorders of environmental changes. They form aragonitic carbonate skeletons that contain relatively high amounts of strontium (Sr²⁺). The ratio of Sr²⁺/calcium (Ca²⁺) has been proved to be useful for paleoclimatic studies since it has been suggested to vary with the seawater temperature. However, no correlation can be established between skeletal Sr²⁺ content and environmental parameters due to the lack of knowledge concerning the extent to which skeletal chemistry is controlled by physiological parameters. In this study, we investigated the pathway of Sr²⁺ incorporation by the scleractinian coral Stylophora pistillata. For this purpose, we used ⁸⁵Sr and a non-destructive NaI γ detector. Sr²⁺ skeletal incorporation was found to be linear during the 9 experimental days of incubation with natural concentrations of Sr²⁺. The incorporation of Sr²⁺ versus external Sr²⁺ concentration was also linear up to 3.42 mM (i.e. a concentration 37.5 times higher than normal seawater concentration). However, the uptake of Sr²⁺ at high concentrations (>1 mM) decreased with an increase in Ca²⁺ concentration in the seawater. Moreover, Verapamil, a Ca²⁺ channel inhibitor, also inhibits the incorporation of Sr²⁺ with the same I_c50 (12 µM) as for Ca²⁺. Incorporation of Sr²⁺ is therefore inversely correlated to the rate of calcification, suggesting interactions between these 2 ions, which should be taken into account during paleoclimatic studies.

KEY WORDS: Corals · Strontium · Calcium · Paleoclimatology