Oxygen isotope variation on a lagoonal platform reef, Heron island, Great Barrier Reef

Abstract

A survey of temperature, salinity and oxygen isotope ratio was conducted on the reefal waters of a lagoonal platform reef, Heron Reef, situated near the southern end of the Great Barrier Reef. The oxygen isotope ratio of the water changed by nearly 2‰ during a 3-week period. Daily variations of 1.4‰ were detected. As the maximum oxygen isotope ratios occurred at low tide, during times of high temperature and high salinity, temperature-induced variation in oxygen isotope ratios of skeletal material was masked. Such a phenomenon can easily explain why previous workers have failed to detect the full range of oxygen isotope ratios in coral skeletons and other calcareous organisms.