Reef-building corals and other carbonate-producing organisms are used extensively as proxies for past variations in global climate based on the elemental and isotopic composition of their skeletons and shells. Typically, biological processes offset the composition of the skeleton from thermodynamic equilibrium with seawater. It is therefore of wide interest to understand the degree to which biological versus inorganic processes control the chemistry of the coral skeleton. We will study the trace element and isotopic manifestations of biological processes in the coral skeletal mineralization process using state-of-the-art ion microprobe analytical equipment that has never before been applied to this important problem.