Effects of growth and dissolution on the fractionation of silicon isotopes by estuarine diatoms

Abstract

Studies of silicon (Si)

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

“…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). 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).…”

Dissolved silicon and its isotopes in the water column of the Bay of Bengal: Internal cycling versus lateral transport

“…(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article. )to typical of open ocean waters; this does not seem to affect the biological 30 e Uptake asSun et al (2014) have reported a comparable value of À1.5 ± 0.36& during cultural production of estuarine diatoms in estuary water of salinity 7. Theproperties of dissolved Si (Si Source and d 30 Si Source ) exiting estuarine waters to the northern shelf and open BoB are estimated using the Steady State model by substituting d 30 Si Steady State in Eq.…”

Impact of human disturbance on the biogeochemical silicon cycle in a coastal sea revealed by silicon isotopes

“…The formation of authigenic clay minerals ( 30 ε rw ) in the sediment has only been estimated to be −2.00‰ in the Peruvian upwelling region (Ehlert et al ). Si isotopic fractionation during the dissolution of BSi ( 30 ε diss ) is also assessed in the literature with an isotope fractionation of −0.55 ± 0.05‰ (Demarest et al ); however, other studies reported no Si isotope fractionation (e.g., Sun et al ; Wetzel et al ; Gao et al ). We tested the influence of this putative fractionation on the distribution of Si isotopes and saw negligible impact (Supporting Information Fig.…”

“…Si isotopes are fractionated in the surface box during diatom production ( 30 ε uptake ), which 30 ε uptake value is reported to be −1.10 AE 0.40‰ (De La Rocha et al 1997) and ranges from −0.54‰ to −2.09‰ for polar and subpolar marine diatoms (Sutton et al 2013). The formation of authigenic clay minerals ( 30 ε rw ) in the sediment has only been estimated to be −2.00‰ in the Peruvian upwelling region fractionation during the dissolution of BSi ( 30 ε diss ) is also assessed in the literature with an isotope fractionation of −0.55 AE 0.05‰ (Demarest et al 2009); however, other studies reported no Si isotope fractionation (e.g., Sun et al 2014;Wetzel et al 2014;Gao et al 2016). We tested the influence of this putative fractionation on the distribution of Si isotopes and saw negligible impact (Supporting Information Fig.…”