Silicon isotopes of deep-sea sponges: new insights into biomineralisation and skeletal structure

Cassarino, Lucie; Coath, C. D.; Xavier, Joana R.; Hendry, Katharine R

doi:10.5194/bg-2018-328

Cited by 8 publications

(25 citation statements)

References 50 publications

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“…2C), are isotopically lighter than expected. The sponge specimens in the study were graded according to degree of secondary silica fusion: the more secondary silica deposited, the greater the isotopic anomaly (Cassarino et al, 2018). These results indicate that, again, there is a different process involved in producing secondary silica "cement" that fuses primary spicules within hexactinellids.…”

Section: Silicon Isotopes In Spongesmentioning

confidence: 93%

“…There are a number of caveats to consider when applying sponge  30 Si to the geological record, including the observed variability in fractionation associated with different biosilicification mechanisms. However, this concern can -to a large part -be assuaged through avoiding potentially anomalous spicules, such as desmas (Hendry et al, 2015), or framework structures (Cassarino et al, 2018). Some palaeoceanographic studies have circumvented potential issues by picking only one form of spicule from marine sediments for archive generation (Fontorbe et al, 2016).…”

Section: Palaeoclimate Applicationsmentioning

confidence: 99%

“…Water DSi silicon isotope ( 30 DSi) analysis methods are fully described in Cassarino et al, 2018. Briefly, silicon was pre-concentrated twice by the additional of sodium hydroxide (1.2% v/v 1M NaOH, followed by 1% v/v 1M NaOH 24 hours later) to precipitate magnesium hydroxide.…”

Section: Seawater Dsi Analysesmentioning

confidence: 99%

“…Mass spectrometric analysis was carried out as for the sponge samples, with the addition of 0.05M HCl and 0.003M H2SO4 to standards and samples prior to analysis to account for any potential matrix effects (Hughes et al, 2011). The ALOHA "300" and "1000" seawater standards were measured alongside the seawater samples to assess analytical accuracy and precision, and yielded values within error of published data ( 30 Si = +1.10 ± 0.15 ‰ and +1.43 ± 0.19 ‰ (2SD internal precision), respectively) (Cassarino et al, 2018;Grasse et al, 2017).…”

Section: Seawater Dsi Analysesmentioning

confidence: 99%

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Silicon isotopic systematics of deep-sea sponge grounds in the North Atlantic

Hendry

Cassarino

Bates

et al. 2019

Quaternary Science Reviews

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Reconstruction of silica cycling in the oceans is key to a thorough understanding of past climates because of the inherent links between the biogeochemistry of silicifiers and sequestration of organic carbon. Diatoms are one of the most important phytoplankton groups in determining export production from surface waters, and rely largely on upwelling deeper waters as a source of dissolved silicon, an essential nutrient for their growth. Quantification of changes in deep water dissolved silicon concentrations in the past allows a more robust understanding of changes in surface nutrient supply and whole-ocean silicon cycling, but cannot be achieved using surfacederived geochemical archives. In the last few years, there has been increasing focus on the use of geochemical archives in siliceous skeletal elements, or spicules, from seafloor-dwelling sponges to fill this gap. The stable silicon isotopic composition of spicules has been shown to be a function of ambient dissolved silicon, providing a potential archive for past changes in bottom water nutrients. However, biomineralisation processes impact silicon isotope fractionation and silica formed by atypical processes (derived from carnivorous sponges, hypersilicified spicules, and giant basal spicules) result in anomalous geochemical signatures. Furthermore, there is considerable scatter in the calibration between spicule silicon isotopes and dissolved silicon in seawater, even when the atypical groups have been removed. Here, we explore this variability further, by examining aggregation and assemblage-level differences in isotopic fractionation, using silicon isotopic measurements of specimens from two monospecific sponge groups (Pheronema carpenteri and Vazella pourtalesi), and one mixed-species population (genus Geodia) from the North Atlantic. Our new data reveal that variability within the monospecific aggregations is less than mixed-species assemblage, pointing towards a genetic control in isotopic fractionation. However, there is still variability within the monospecific aggregations, which cannot be explained by macroscale environmental differences: such variability is likely a reflection of the physiological health of the individuals, or highly localised heterogeneities in sponge habitats. Other challenges remain in the interpretation of spicule silicon isotopes as proxies for dissolved silicon changes through time, especially when investigating periods of Earth history that extend back considerably further than the residence time of dissolved silicon in the oceans. Despite all the questions still surrounding the use of sponge silicon isotopes in palaeoceanographic applications, they are still the only known archive of bottom water dissolved silicon. Continued efforts to understanding sponge biomineralisation and to incorporate silicon isotopes into oceanic models will help to improve further the reliability of the archive.

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Section: Silicon Isotopes In Spongesmentioning

confidence: 93%

Section: Palaeoclimate Applicationsmentioning

confidence: 99%

Section: Seawater Dsi Analysesmentioning

confidence: 99%

Section: Seawater Dsi Analysesmentioning

confidence: 99%

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Silicon isotopic systematics of deep-sea sponge grounds in the North Atlantic

Hendry

Cassarino

Bates

et al. 2019

Quaternary Science Reviews

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“…The DSi concentrations of the fresh medium, post-culture medium (D. grandis only), and organic enrichment medium were measured using a molybdate blue spectrophotometric method (Hach Lange), with an estimated precision of 3% based on replicate measurements of a SiO 2 standard (<0.1% alkali fluorosilicate). The artificial seawater medium was prepared in duplicate for isotopic analysis using a magnesium co-precipitation method (Cassarino et al, 2018): Si was pre-concentrated by the addition of 1.2% v/v 1M sodium hydroxide (NaOH), followed by 1% v/v 1M NaOH after 24 hours. The precipitate was rinsed with 1mM NaOH before dissolution in 6N in-house distilled HCl, dilution in Milli-Q water, and purification using cation exchange resins.…”

Section: Methodsmentioning

confidence: 99%

The silicon isotopic composition of choanoflagellates: implications for a mechanistic understanding of isotopic fractionation during biosilicification

Marron¹,

Cassarino²,

Hatton³

et al. 2019

Preprint

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Abstract. The marine silicon cycle is intrinsically linked with carbon cycling in the oceans via biological production of silica by a wide range of organisms. The stable silicon isotopic composition (denoted by &#948;30Si) of siliceous microfossils extracted from sediment cores can be used as an archive of past oceanic silicon cycling. However, the silicon isotopic composition of biogenic silica has only been measured in diatoms, sponges and radiolarians, and isotopic fractionation relative to seawater is entirely unknown for many other silicifiers. Furthermore, the biochemical pathways and mechanisms that determine isotopic fractionation during biosilicification remain poorly understood. Here, we present the first measurements of the silicon isotopic fractionation during biosilicification by loricate choanoflagellates, a group of protists closely related to animals. We cultured two species of choanoflagellates, Diaphanoeca grandis and Stephanoeca diplocostata, which showed consistently greater isotopic fractionation (approximately &#8722;5 to &#8722;7&#8201;&#8240;) than cultured diatoms (&#8722;0.5 to &#8722;2&#8201;&#8240;). Instead, choanoflagellate silicon isotopic fractionation appears to be more similar to sponges grown under similar DSi concentrations. Our results highlight that there is a taxonomic component to silicon isotope fractionation during biosilicification, possibly via a shared or related biochemical transport pathway. These findings have implications for the use of biogenic silica &#948;30Si produced by different silicifiers as proxies for past oceanic change.

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Using Stable Isotopes to Disentangle Marine Sedimentary Signals in Reactive Silicon Pools

Pickering

Cassarino

Hendry

et al. 2020

Geophysical Research Letters

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Many studies use sedimentary biogenic silica (bSiO2) stable isotopes (e.g., δ30Si) as paleoproxies but neglect signals from other sedimentary reactive SiO2 phases. We quantified δ30Si for multiple reactive Si pools in coastal river‐plume sediments, revealing up to −5‰ difference between acid‐leachable and alkaline‐digestible amorphous SiO2. Thus, previous studies have missed valuable information on early diagenetic products and, in cases where sediments were not cleaned, potentially biased bSiO2 δ30Si values. Acid‐leachable δ30Si, that is, from authigenic products, are the result of either multistep fractionation from a bSiO2 source or an ~2‰ fractionation (consistent with metal hydroxide formation) from slowly dissolving lithogenic SiO2. This analysis also suggests that sedimentary diatom bSiO2, which has increased regionally in the last half‐century, is the critical substrate of early authigenic Si precipitates. Regional eutrophication, which has stimulated sedimentary bSiO2 accumulation, may have facilitated additional sequestration of both sedimentary Si and cations from early diagenetic products.

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Silicon isotopes of deep-sea sponges: new insights into biomineralisation and skeletal structure

Cited by 8 publications

References 50 publications

Silicon isotopic systematics of deep-sea sponge grounds in the North Atlantic

Silicon isotopic systematics of deep-sea sponge grounds in the North Atlantic

The silicon isotopic composition of choanoflagellates: implications for a mechanistic understanding of isotopic fractionation during biosilicification

Using Stable Isotopes to Disentangle Marine Sedimentary Signals in Reactive Silicon Pools

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