During the past century, the sediment deposition rate has been assessed by measuring excess 210 Pb activity in a sediment core sampled in the harbour area of the Papeete Lagoon (Tahiti, French Polynesia). Dated sediment samples were analysed following a sequential extraction method to quantify five sedimentary phosphorus pools: loosely sorbed or exchangeable phosphorus, ferric iron-bound phosphorus, authigenic calcium carbonate associated phosphorus, detrital apatite and detritic inorganic phosphorus, and organic phosphorus. Results from sediment dating showed the core to cover the period from 1865 to 1995, with a sharp change around 1957 corresponding to a doubling in sediment deposition rates. From the bottom to the top of the core, concentrations decreased for authigenic calcium carbonate-associated phosphorus, were almost constant for exchangeable phosphorus, and increased significantly for iron-bound phosphorus, detritic inorganic phosphorus and organic phosphorus. As a consequence, the calculated phosphorus total accumulation rate was multiplied by four from top to bottom. Those trends were related to modifications in the relative importance of the five phosphorus reservoirs, especially for organic phosphorus, which contribution increased to 30% of total phosphorus in recent sediments. From the sequential extraction approach it is possible to estimate that phosphorus with a terrestrial origin represented 54% of total phosphorus in recent sediment, while it only represented 30% at the beginning of the century. Present particulate phosphorus inputs were also assessed from a sediment trap approach and a budget of phosphorus burial efficiency is proposed. © 2001 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SAS Résumé − Reconstitution géochronologique de l'évolution des apports en phosphore particulaire durant le dernier siècle dans le lagon de Papeete (Polynésie française). Le taux de sédimentation a été évalué par la mesure de l'activité du 210 Pb en excès dans une carotte de sédiment prélevée dans la zone portuaire du lagon de Papeete (Tahiti, Polynésie française). Les échantillons de sédiments datés ont été soumis à une extraction séquentielle afin de déterminer cinq fractions sédimentaires de phosphore : faiblement adsorbé ou échangeable, associé au fer ferrique, lié au carbonate de calcium authigène, détritique et organique. Les résultats de datation montrent que la carotte couvre la période 1865-1996, avec un changement majeur vers 1957 correspondant à un doublement du taux de sédimentation. Entre la base et le haut de la carotte, les concentrations diminuent pour le phosphore lié au carbonate de sodium, restent *Correspondence and reprints: fax: +687 26 4326. E-mail address: fichez@noumea.ird.nc (R. FICHEZ). © 2001 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SAS. Tous droits réservés S0399178400011233/FLA 1 OCEANOLOGICA ACTA ⋅ VOL. 24 -No. 1constantes pour le phosphore faiblement échangeable, et augmentent pour le phosphore associé au fer ferrique, le phosphore détriti...
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