Cadmium.to.calcium rations will be determined in corals and in the aragonite.depositing green alga Halimeda in Holocene reefs and bioherms from the Great Barrier Reef, Australia. The objectives are: (1) to determine Holocene variations in Cd/Ca ratios in outer shelf coral reefs, including records from reef initiation 8500 ybp to the present in cores representing leeward to windward environments in individual reefs and from reefs spanning a range of latitudes; (2) to determine variations in seasonality in Cd/Ca ratios in Holocene Great Barrier Reef corals, comparing contemporary and selected historical corals; (3) to determine Holocene variations in Cd/Ca ratios in Great Barrier Reef Halimeda bioherms, from initiation (.2000 y before coral reef initiation in the same latitude) to the present; and (4) to interpret Cd/Ca records from coral and Halimeda to test hypotheses about the role of changing nutrient supply in controlling Holocene reef and bioherm growth in the Great Barrier Reef. Careful attention will be given to identifying and isolating trace element signals due to terrestrial, rather than oceanographic influences, and to alteration. Graphite furnace and flame atomic absorption spectrophotometry will be used to determine Cd/Ca, Mn/Ca, Sr/Ca, and Mg/Ca ratios; X.ray diffraction spectroscopy will be used to determine mineralogy.
