PRIMARY PRODUCTION, CALCIFICATION, AND AIR-SEA CO2 FLUXES OF A MACROALGAL-DOMINATED CORAL-REEF COMMUNITY (MOOREA, FRENCH-POLYNESIA)

Community metabolism and air-sea carbon dioxide (CO2) fluxes were inve stigated in July 1992 on a fringing reef at Moorea (French Polynesia). The benthic community was dominated by macroalgae (85% substratum cov er) and comprised of Phaeophyceae Padina tenuis (Bory), Turbinaria orn ata (Turner) J. Agardh, and Hydroclathrus clathratus Bory (Howe); Chlo rophyta Halimeda incrassata f. ovata J. Agardh (Howe); and Ventricaria ventricosa J. Agardh (Olsen et West), as well as several Rhodophyta ( Actinotrichia fragilis Forskal (Borgesen) and several species of encru sting coralline algae). Algal biomass was 171 g dry weight.m(-2). Comm unity gross production (P-g), respiration (R), and net calcification ( G) were measured in an open-top enclosure. P-g and R were respectively 248 and 240 mmol CO2 . m(-2).d(-1), and there was a slight net dissol ution of CaCO3 (0.8 mmol.m(-2).d(-1)). This site was a sink for atmosp heric CO2 (10 +/- 4 mmol CO2.m(-2).d(-1)), and the analysis of data fr om the literature suggests that this is a general feature of algal-dom inated reefs. Measurement of air-sea CO2 fluxes in open water close to the enclosure demonstrated that changes in small-scale hydrodynamics can lead to misleading conclusions. Net CO2 evasion to the atmosphere was measured on the fringing reef due to changes in the current patter n that drove water from the barrier reef (a CO2 source) to the study s ite.