Isotopic constraints on the Si-biogeochemical cycle of the Antarctic Zone in the Kerguelen area (KEOPS)

Fripiat, François; Cavagna, A.-J.; Savoye, Nicolas; Dehairs, Frank; André, Luc; Cardinal, Damien

doi:10.1016/j.marchem.2010.08.005

Cited by 89 publications

(176 citation statements)

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“…In addition, isotopic effects of BSi dissolution would not be measurable in waters below 100 m in that the amount of regenerated Si would be too small to influence the isotopic composition of the large dissolved Si(OH) 4 reservoir. e upt values following the steady state model are indistinguishable from the average of 21.260.3& estimated from field investigations in both the Southern Ocean (Fripiat et al 2011, and references therein) and the Pacific Ocean (e.g., Reynolds et al 2006;Beucher et al 2008). The narrow range of estimations for in situ 30 e upt indicates that mixed diatom assemblages in a natural system may have reduced the speciesdependent variability (Fripiat et al 2014), which was also observed for N isotope fractionation during NO 3 utilization (Sigman et al 2009).…”

Section: Dynamics Of Dissolved Si Isotopes In the East China Sea In Smentioning

confidence: 65%

“…The main processes controlling seawater d 30 Si Si(OH)4 signatures are Si(OH) 4 utilization by diatoms, biogenic silica (BSi) dissolution, and water mass mixing. While previous studies revealed that diatoms preferentially incorporate lighter Si isotopes from surrounding seawater with a relatively constant fractionation factor ( 30 e upt ) of 21.1& (De La Rocha et al 1997;Fripiat et al 2011, and references therein), new culture experiments showed that the 30 e upt of polar/subpolar diatom species varies within a relatively large range of 20.5 to 22.1& (Sutton et al 2013). On the other hand, based on experiments Demarest et al (2009) suggested that the lighter Si isotopes are preferentially released into seawater during BSi dissolution with a fractionation factor ( 30 e diss ) of 20.55&, whereas near zero values of 30 e diss were observed in laboratory dissolution experiments using, respectively, an estuarine diatom species (20.12&; Sun et al 2014) and diatom opal extracted from sediments (10.14&; Wetzel et al 2014).…”

mentioning

confidence: 94%

“…On the other hand, based on experiments Demarest et al (2009) suggested that the lighter Si isotopes are preferentially released into seawater during BSi dissolution with a fractionation factor ( 30 e diss ) of 20.55&, whereas near zero values of 30 e diss were observed in laboratory dissolution experiments using, respectively, an estuarine diatom species (20.12&; Sun et al 2014) and diatom opal extracted from sediments (10.14&; Wetzel et al 2014). Although no fractionation occurs during water mass mixing, this physical process primarily determines the initial Si(OH) 4 concentration and its isotopic composition for diatom growth, which are not spatially and/or temporally homogenous in a given oceanic system (Cardinal et al 2005;Fripiat et al 2011), in particular in marginal seas with highly dynamic hydrographic conditions (Cao et al 2012).…”

mentioning

confidence: 97%

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Dissolved silicon isotopic compositions in the East China Sea: Water mass mixing vs. biological fractionation

Cao

Dai

2015

Limnology & Oceanography

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Section: Dynamics Of Dissolved Si Isotopes In the East China Sea In Smentioning

confidence: 65%

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confidence: 94%

mentioning

confidence: 97%

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Dissolved silicon isotopic compositions in the East China Sea: Water mass mixing vs. biological fractionation

Cao

Dai

2015

Limnology & Oceanography

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“…A value of 30 e at -1.1 % was determined in vitro (De La Rocha et al 1997) and in situ (Fripiat et al 2011) for marine diatoms, and validated in lakes Opfergelt et al 2011).…”

Section: Stable Isotope Samplesmentioning

confidence: 99%

High concentrations of amorphous, biogenic Si (BSi) in the sediment of a small high-latitude lake: implications for biogeochemical Si cycling and for the use of BSi as a paleoproxy

et al. 2014

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The concentration of biogenic silica (BSi) in soils and sediments may be studied for several purposes, most notably either as a paleo-environmental proxy or to clarify the transport of weathering-derived Si within the biogeosphere. With this in mind, we explored the reasons behind the very high BSi concentration (average 250 mg Si g -1 dry mass) in the sediment of a small, highlatitude lake in Finnish Lapland, Lake Kuutsjärvi, using bulk BSi and stable Si isotope analysis of major Si pools in the lake and its drainage area. The high BSi content of the sediment was relatively stable over the past few hundred years and recent changes in the food web of the lake were not clearly reflected in the data. The origin of the sedimentary BSi was not solely autochthonous diatom production: extraneous sources accounted for possibly as much as 54-88 % (isotope analysis). A main reason for the high BSi content appeared to be the transport of older deposits of diatom material from the drainage area into the current lake basin, although other factors such as good preservation conditions may have contributed. Although our results indicate that small high-latitude lakes may be hot-spots in the burial of BSi, more information is needed on the processes that affect the translocation of BSi from the drainage area to the aquatic system. Caution is advisable when past lake conditions are inferred from sedimentary BSi only.

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“…However, the calibration of this proxy in the modern ocean has still not been fully achieved and processes such as Si(OH) 4 supply and bSiO 2 dissolution can bias the expected relationship between Si(OH) 4 concentration and δ 30 Si composition (Demarest et al, 2009). For example, contemporary isotopic compositions of biogenic silica vary widely in the Southern Ocean (−0.5 to +2.5 ‰), while the isotopic range of silicic acid is smaller (from +1.5 to 3.4 ‰) Cardinal et al, 2005Fripiat et al, 2011a;Cavagna et al, 2011). None of the existing isotopic fractionation models are capable of reproducing these differences.…”

Section: F Fripiat Et Al: Si-isotopic Composition In the Southern Omentioning

confidence: 99%

Processes controlling the Si-isotopic composition in the Southern Ocean and application for paleoceanography

et al. 2012

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Abstract. Southern Ocean biogeochemical processes have an impact on global marine primary production and global elemental cycling, e.g. by likely controlling glacial-interglacial pCO 2 variation. In this context, the natural silicon isotopic composition (δ 30 Si) of sedimentary biogenic silica has been used to reconstruct past Si-consumption:supply ratios in the surface waters. We present a new dataset in the Southern Ocean from a IPY-GEOTRACES transect (BonusGoodHope) which includes for the first time summer δ 30 Si signatures of suspended biogenic silica (i) for the whole water column at three stations and (ii) in the mixed layer at seven stations from the subtropical zone up to the Weddell Gyre. In general, the isotopic composition of biogenic opal exported to depth was comparable to the opal leaving the mixed layer and did not seem to be affected by any diagenetic processes during settling, even if an effect of biogenic silica dissolution cannot be ruled out in the northern part of the Weddell Gyre. We develop a mechanistic understanding of the processes involved in the modern Si-isotopic balance, by implementing a mixed layer model. We observe that the accumulated biogenic silica (sensu Rayleigh distillation) should satisfactorily describe the δ 30 Si composition of biogenic silica exported out of the mixed layer, within the limit of the current analytical precision on the δ 30 Si. The failures of previous models (Rayleigh and steady state) become apparent especially at the end of the productive period in the mixed layer, when biogenic silica production and export are low. This results from (1) a higher biogenic silica dissolution:production ratio imposing a lower net fractionation factor and (2) a higher Si-supply:Si-uptake ratio supplying light Si-isotopes into the mixed layer. The latter effect is especially expressed when the summer mixed layer becomes strongly Si-depleted, together with a large vertical silicic acid gradient, e.g. in the Polar Front Zone and at the Polar Front.

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Isotopic constraints on the Si-biogeochemical cycle of the Antarctic Zone in the Kerguelen area (KEOPS)

Cited by 89 publications

References 65 publications

Dissolved silicon isotopic compositions in the East China Sea: Water mass mixing vs. biological fractionation

Dissolved silicon isotopic compositions in the East China Sea: Water mass mixing vs. biological fractionation

High concentrations of amorphous, biogenic Si (BSi) in the sediment of a small high-latitude lake: implications for biogeochemical Si cycling and for the use of BSi as a paleoproxy

Processes controlling the Si-isotopic composition in the Southern Ocean and application for paleoceanography

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