DIRECT MEASUREMENTS OF CARBON AND CARBONATE EXPORT FROM A CORAL-REEF ECOSYSTEM (MOOREA ISLAND, FRENCH-POLYNESIA)

The export of carbon and carbonate from coral reefs was investigated t hrough a multidisciplinary investigation of the hydrological, geochemi cal, sedimentological and biological features of Tiahura reef on the n orthwestern coast of Moorea Island (French Polynesia). The hydrology o f the fore-reef is characterised by prevailing longshore western curre nts and a strong thermocline. As revealed by turbidity structures (ben thic and intermediate nepheloid layers) and by the amount of particles collected by near-bottom sediment traps, horizontal and downslope adv ections of particles dominate over offshore vertical transport. The ex ported material is rich in carbonate (ca. 80%) and poor in organic mat ter (ca. 4%). Sedimentation rates at 430 m depth, i.e. definitive expo rt, reached 209.6 mg m(-2) d(-1) (dry weight). Estimates of carbon and carbonates export for Tiahura reef also reported here represent respe ctively 47% and 21% of the organic and inorganic carbon produced withi n the reef.