Intercolony variability of skeletal oxygen and carbon isotope ratios of Porites corals: thermostated tank experiment and field observation

Abstract

The skeletal oxygen isotope ratio of Porites corals, together with the carbon isotope ratio, is the most frequently used proxy of past seawater temperature and composition for tropical oceans. We conducted tank experiments in which we grew Porites spp. colonies in thermostated seawater at five temperature settings between 21 and 29 degree C. We also examined oxygen and carbon isotope ratios of Porites corals collected from Sekisei Reef of southern Ryukyu Islands, Japan. Growth-rate-related kinetic isotope effects found in both the cultured corals and the deep slower-growing corals may be, at least partly, attributed to low light condition.