Effect of pCO2 and temperature on the boron isotopic composition of the zooxanthellate coral Acropora sp

Culture experiments were carried out with Acropora sp. (a branching scleractinian coral) in seawater at two pCO^sub 2^ conditions (438 and 725 µatm) and two temperatures (25 and 28 °C) in order to establish the pH and temperature dependence of the boron isotopic composition of the skeleton. A clear pCO^sub 2^ effect, but no temperature effect, on the coral boron isotope composition is seen. For corals cultured at "normal pCO^sub 2^" (438 µatm), the δ^sup 11^B of the skeleton was 24.0±0.2[per thousand] at 25 °C, and 23.9±0.3[per thousand] at 28 °C. The values of δ^sup 11^B measured for corals cultured at higher pCO^sub 2^ (725 µatm) were lower: 22.5±0.1[per thousand], and 22.8±0.1[per thousand] at 25 and 28 °C, respectively. The δ^sup 11^B of corals cultivated at both high and normal pCO^sub 2^ conditions are consistent with a dominant pH control, and are very close to that calculated from theoretical considerations. Thus, the corals do not seem to significantly alter ambient seawater for calcification with respect to pH. Co-variation between boron and carbon isotope values is explored.[PUBLICATION ABSTRACT]