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Titolo:
The benthic silica cycle in the Northeast Atlantic: annual mass balance, seasonality, and importance of non-steady-state processes for the early diagenesis of biogenic opal in deep-sea sediments
Autore:
Ragueneau, O; Gallinari, M; Corrin, L; Grandel, S; Hall, P; Hauvespre, A; Lampitt, RS; Rickert, D; Stahl, H; Tengberg, A; Witbaard, R;
Indirizzi:
IUEM, UMR CNRS 6539, F-29280 Plouzane, France IUEM Plouzane France F-29280 EM, UMR CNRS 6539, F-29280 Plouzane, France GEOMAR, Res Ctr, Dept Marine Environm Geol, D-24148 Kiel, Germany GEOMAR Kiel Germany D-24148 Marine Environm Geol, D-24148 Kiel, Germany Univ Gothenburg, Dept Analyt & Marine Chem, SE-41296 Gothenburg, Sweden Univ Gothenburg Gothenburg Sweden SE-41296 , SE-41296 Gothenburg, Sweden Southampton Oceanog Ctr, Southampton SO14 3ZH, Hants, England Southampton Oceanog Ctr Southampton Hants England SO14 3ZH Hants, England NIOZ, NL-1790 AB Den Burg, Netherlands NIOZ Den Burg Netherlands NL-1790AB Z, NL-1790 AB Den Burg, Netherlands
Titolo Testata:
PROGRESS IN OCEANOGRAPHY
fascicolo: 1-4, volume: 50, anno: 2001,
pagine: 171 - 200
SICI:
0079-6611(2001)50:1-4<171:TBSCIT>2.0.ZU;2-N
Fonte:
ISI
Lingua:
ENG
Soggetto:
DISSOLUTION RATES; SOUTHERN-OCEAN; EQUATORIAL PACIFIC; PARTICLE-FLUX; MARINE-SEDIMENTS; INDIAN-OCEAN; SARGASSO-SEA; KINETICS; WATER; ACCUMULATION;
Tipo documento:
Review
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
112
Recensione:
Indirizzi per estratti:
Indirizzo: Ragueneau, O IUEM, UMR CNRS 6539, Pl Nicolas Copernic,Technopole Brest Iroise, F-29280 Plouzane, France IUEM Pl Nicolas Copernic,Technopole Brest Iroise Plouzane France F-29280
Citazione:
O. Ragueneau et al., "The benthic silica cycle in the Northeast Atlantic: annual mass balance, seasonality, and importance of non-steady-state processes for the early diagenesis of biogenic opal in deep-sea sediments", PROG OCEAN, 50(1-4), 2001, pp. 171-200

Abstract

Within the framework of the EU-funded BENGAL programme, the effects of seasonality on biogenic silica early diagenesis have been studied at the Porcupine Abyssal Plain (PAP), an abyssal locality located in the northeast Atlantic Ocean. Nine cruises were carried out between August, 1996 and August 1998. Silicic acid (DSi) increased downward from 46.2 to 213 muM (mean of 27profiles). Biogenic silica (BSi) decreased from ca. 2% near the sediment-water interface to <1% at depth. Benthic silicic acid fluxes as measured from benthic chambers were close to those estimated from non-linear DSi porewater gradients. Some 90% of the dissolution occurred within the top 5.5 cm of the sediment column, rather than at the sediment-water interface and the annual DSi efflux was close to 0.057 Mol Si m(-2) yr(-1). Biogenic silica accumulation was close to 0.008 mol Si m(-2) yr(-1) and the annual opal delivery reconstructed from sedimentary fluxes, assuming steady state, was 0.065 Mol Si m(-2) yr(-1). This is in good agreement with the mean annual opal flux determined from sediment trap samples, averaged over the last decade (0.062 mol Si m(-2) yr(-1)). Thus ca. 12% of the opal flux delivered to the seafloor get preserved in the sediments. A simple comparison between the sedimentation rate and the dissolution rate in the uppermost 5.5 cm of the sediment column suggests that there should be no accumulation of opal in PAP sediments. However, by combining the BENGAL high sampling frequency with our experimental results on BSi dissolution, we conclude that non-steady state processes associated with the seasonal deposition of fresh biogenic particles may well play a fundamental role in the preservation of BSi in these sediments. This comes about though the way seasonal variability affects the quality of the biogenic matter reaching the seafloor. Hence it influences the intrinsic dissolution properties of the opal at the seafloor and also the part played by non-local mixing events by ensuring the rapid transport ofBSi particles deep into the sediment to where saturation is reached. (C) 2001 Elsevier Science Ltd. All rights reserved.

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Documento generato il 30/11/20 alle ore 16:51:10