Rodier Martine auteur aut IRD Pinazo C. auteur aut IRD Seceh C. auteur aut IRD Varillon David auteur aut IRD text journalArticle eng text/pdf born digital access This study reports the first measurements of nitrogen uptake and new data on carbon fixation (N-15/C-13 incorporation) for two size-fractionated phytoplankton (<2 mu m and >2 mu m), on organic matter, and phytoplankton stocks in Ahe lagoon. Data were collected between November and December 2017, during the hot season with prevailing trade winds. Ammonium and nitrate uptake data (7.58 to 39.81 and 1.80 to 21.43 mu mol N m(-3) h(-1), respectively) suggest a rapid turn-over of N-nutrients in the water column and show that primary production was largely sustained by recycled nitrogen providing 68% of the pelagic N demand. These results highlight the spatial heterogeneity of the measured processes linked to the local hydrodynamics, exhibiting higher regenerated production in the more exploited southwestern part of the lagoon and a higher proportion of new production in the north. Intense nutrient recycling appears to promote nanophytoplankton production which is critical for pearl oyster growth. specialized Nitrogen uptake Primary production Phytoplankton composition Atoll lagoon Pearl farming French Polynesia POLYNESIE FRANCAISE AHE 040 032 034 167 112352 [11 p.] 2021 0025-326X https://www.documentation.ird.fr/hor/fdi:010082093 10.1016/j.marpolbul.2021.112352 0025-326X [F B010082093] https://www.documentation.ird.fr/hor/fdi:010082093 https://www.documentation.ird.fr/intranet/publi/2021-07/010082093.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2021-07-02 2025-02-24 fdi:010082093 fre