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Particulate organic carbon export fluxes and size-fractionated POC/234Th ratios in the Ligurian, Tyrrhenian and Aegean Seas

TitoloParticulate organic carbon export fluxes and size-fractionated POC/234Th ratios in the Ligurian, Tyrrhenian and Aegean Seas
Tipo di pubblicazioneArticolo su Rivista peer-reviewed
Anno di Pubblicazione2006
AutoriSpeicher, E.A., Moran S.B., Burd A.B., Delfanti Roberta, Kaberi H., Kelly R.P., Papucci C., Smith J.N., Stavrakakis S., Torricelli L., and Zervakis V.
RivistaDeep-Sea Research Part I: Oceanographic Research Papers
Volume53
Paginazione1810-1830
ISSN09670637
Parole chiaveAegean Sea, carbon, carbon cycle, carbon flux, Ligurian Sea, Mediterranean Sea, Particle size analysis, Particles (particulate matter), Particulate organic carbon, Phytoplankton dynamics, Sinking rates, Surface waters, Thorium, thorium isotope, Tyrrhenian Sea
Abstract

Measurements of 234Th/238U disequilibria and particle size-fractionated (1, 10, 20, 53, 70, 100 μm) organic C and 234Th were made to constrain estimates of the export flux of particulate organic C (POC) from the surface waters of the Ligurian, Tyrrhenian and Aegean Seas in March-June 2004. POC exported from the surface waters (75-100 m depth) averaged 9.2 mmol m-2 d-1 in the Ligurian and Tyrrhenian Seas (2.3±0.5-14.9±3.0 mmol m-2 d-1) and 0.9 mmol m-2 d-1 in the Aegean Sea. These results are comparable to previous measurements of 234Th-derived and sediment-trap POC fluxes from the upper 200 m in the Mediterranean Sea. Depth variations in the POC/234Th ratio suggest two possible controls. First, decreasing POC/234Th ratios with depth were attributed to preferential remineralization of organic C. Second, the occurrence of maxima or minima in the POC/234Th ratio near the DCM suggests influence by phytoplankton dynamics. To assess the accuracy of these data, the empirical 234Th-method was evaluated by quantifying the extent to which the 234Th-based estimate of POC flux, PPOC, deviates from the true flux, FPOC, defined as the p-ratio (p-ratio=PPOC/FPOC=STh/SPOC, where S=particle sinking rate). Estimates of the p-ratio made using Stokes' Law and the particle size distributions of organic C and 234Th yield values ranging from 0.93-1.45. The proximity of the p-ratio to unity implies that differences in the sinking rates of POC- and 234Th-carrying particles did not bias 234Th-normalized POC fluxes by more than a factor of two. © 2006 Elsevier Ltd. All rights reserved.

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URLhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-33751005816&doi=10.1016%2fj.dsr.2006.08.005&partnerID=40&md5=464ae9635ac799899cfc48a786095b60
DOI10.1016/j.dsr.2006.08.005
Citation KeySpeicher20061810