Using geochronology to reconstruct the evolution of particulate phosphorusinputs during the past century in the Papeete Lagoon (French Polynesia)

Citation
P. Harris et al., Using geochronology to reconstruct the evolution of particulate phosphorusinputs during the past century in the Papeete Lagoon (French Polynesia), OCEANOL ACT, 24(1), 2001, pp. 1-10
Citations number
43
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Aquatic Sciences
Journal title
OCEANOLOGICA ACTA
ISSN journal
0399-1784 → ACNP
Volume
24
Issue
1
Year of publication
2001
Pages
1 - 10
Database
ISI
SICI code
0399-1784(2001)24:1<1:UGTRTE>2.0.ZU;2-2
Abstract
During the past century, the sediment deposition rate has been assessed by measuring excess Pb-210 activity in a sediment core sampled in the harbour area of the Papeete Lagoon (Tahiti, French Polynesia). Dated sediment sampl es were analysed following a sequential extraction method to quantify five sedimentary phosphorus pools: loosely sorbed or exchangeable phosphorus, fe rric iron-bound phosphorus, authigenic calcium carbonate associated phospho rus, detrital apatite and detritic inorganic phosphorus, acid organic phosp horus. Results from sediment dating showed the core to cover the period fro m 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, conc entrations decreased for authigenic calcium carbonate-associated phosphorus , were almost constant for exchangeable phosphorus, and increased significa ntly for iron-bound phosphorus, detritic inorganic phosphorus and organic p hosphorus. As a consequence, the calculated phosphorus total accumulation r ate 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 appro ach it is possible to estimate that phosphorus with a terrestrial origin re presented 54% of total phosphorus in recent sediment, while it only represe nted 30% at the beginning of the century. Present particulate phosphorus in puts were also assessed from a sediment trap approach and a budget of phosp horus burial efficiency is proposed. (C) 2001 Ifremer/CNRS/IRD/Editions sci entifiques et medicales Elsevier SAS.