EXCESS PRIMARY PRODUCTION, CALCIFICATION AND NUTRIENT FLUXES OF A PATCH REEF (TIKEHAU ATOLL, FRENCH-POLYNESIA)

Community metabolism (primary production, respiration and calcificatio n), nutrient budgets, and export of particulate organic matter of a pa tch reef were investigated in the lagoon of Tikehau atoll (Tuamotu Arc hipelago, French Polynesia). The pinnacle studied displays strong carb onate dissolution of the top surface layer, estimated to be up to -37 g CaCO3 m(-2) d(-1). The net production is negative (-3.2 g C m(-2) d( -1)) and the gross primary production was estimated to be 4.4 g C m(-2 ) d(-1). So the lagoonal pinnacle appears to be a sink for particulate organic matter, which is trapped by the reef frame, and a source of n itrate for downstream lagoonal waters.