Nutrient fluxes between water column and sediments: Potential influence of the pearl oyster culture

This study quantifies benthic nutrient fluxes and sedimentation rates in the Ahe Atoll lagoon (French Polynesia), in two stations located under pearl oyster frames, and two control stations away from the pearl culture facility. Dissolved inorganic nitrogen fluxes ranged between 2 and 35 μmol N m−2 h−1 and Soluble Reactive Phosphorus varied between −3 and 8.2 μmol P m−2 h−1. Particulate sedimentation rates beneath the oysters were approximately five times higher than in the control zone and the percentage of small particles (⩽63 μm) were about the twice. In contrast, sediment composition was similar under and outside the direct influence of oyster frames. In this ecosystem, where primary production is dependent on the available nitrogen, our study revealed that, while highly variable, benthic fluxes could sometimes contribute up to 28% of the nitrogen demand for primary production.