The effect of chemical pretreatment of sediment upon foraminiferal‐based proxies

Feldmeijer, Wouter; Metcalfe, Brett; Scussolini, Paolo; Arthur, Kristina

doi:10.1002/ggge.20233

Cited by 21 publications

(19 citation statements)

References 103 publications

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“…As with any foraminifera-based work, sediment disaggregation and sieving is required; detergents and disaggregation agents (Feldmeijer et al 2013) may have high levels of boron and should be avoided.…”

Section: Sample Size and Preparationmentioning

confidence: 99%

Boron Isotopes in Foraminifera: Systematics, Biomineralisation, and CO2 Reconstruction

Rae

2017

Advances in Isotope Geochemistry

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The boron isotope composition of foraminifera provides a powerful tracer for CO 2 change over geological time. This proxy is based on the equilibrium of boron and its isotopes in seawater, which is a function of pH. However while the chemical principles underlying this proxy are well understood, its reliability has previously been questioned, due to the difficulty of boron isotope (d 11 B) analysis on foraminferal samples and questions regarding calibrations between d 11 B and pH. This chapter reviews the current state of the d 11 B-pH proxy in foraminfera, including the pioneering studies that established this proxy's potential, and the recent work that has improved understanding of boron isotope systematics in foraminifera and applied this tracer to the geological record. The theoretical background of the d 11 B-pH proxy is introduced, including an accurate formulation of the boron isotope mass balance equations. Sample preparation and analysis procedures are then reviewed, with discussion of sample cleaning, the potential influence of diagenesis, and the strengths and weaknesses of boron purification by column chromatography versus microsublimation, and analysis by NTIMS versus MC-ICPMS. The systematics of boron isotopes in foraminifera are discussed in detail, including results from benthic and planktic taxa, and models of boron incorporation, fractionation, and biomineralisation. Benthic taxa from the deep ocean have d 11 B within error of borate ion at seawater pH. This is most easily explained by simple incorporation of borate ion at the pH of seawater. Planktic foraminifera have d 11 B close to borate ion, but with minor offsets. These may be driven by physiological influences on the Electronic supplementary material The online version of this chapter

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Section: Sample Size and Preparationmentioning

confidence: 99%

Boron Isotopes in Foraminifera: Systematics, Biomineralisation, and CO2 Reconstruction

Rae

2017

Advances in Isotope Geochemistry

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“…One of the main complications of the biogenic carbonate pretreatment debate is the lack of a consistent standard practice 20,60 . There are inconsistencies in the concentrations of chemical used, in the temperatures used, and in the duration of exposure time (Table 1).…”

Section: Discussionmentioning

confidence: 99%

“…Pretreatment of biogenic carbonates for O and C isotope analysis using conventional acid digestion followed by mass spectrometry is aimed at preventing the reaction between any organic matter and H 3 PO 4 (phosphoric acid) used to liberate CO 2 from the skeletal carbonate 20,21 . Organics also tend to inhibit complete dissolution of the carbonate material during isotopic analysis 22 .…”

Section: Introductionmentioning

confidence: 99%

Effect of removal of organic material on stable isotope ratios in skeletal carbonate from taxonomic groups with complex mineralogies

Key

Smith

Phillips

et al. 2020

Rapid Comm Mass Spectrometry

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Rationale Stable oxygen and carbon isotope ratios are one of the most accurate ways of determining environmental changes in the past, which are used to predict future environmental change. Biogenic carbonates from marine organisms are the most common source of samples for stable isotope analysis. Before they are analyzed by mass spectrometry, any organic material is traditionally removed by one of three common pretreatment methods: roasting, bleaching, or with hydrogen peroxide at various strengths and durations. Methods This study compares δ18O and δ13C values in a control with no pretreatment with those from five different pretreatment methods using conventional acid digestion mass spectrometry. The objectives are to: assess the impact of the most common pretreatment methods on δ18O and δ13C values from (1) taxonomically underrepresented groups in previous studies, and (2) those that precipitate a wide range of biomineralogies, in the debate of whether to pretreat or not to pretreat. We analyzed the following biomineralogically complex temperate marine organisms from southern New Zealand: four species of bryozoans, four species of molluscs, two species of arthropods, and one species each of annelid, red alga, brachiopod, and echinoderm (test plates and spines treated separately). These species precipitate aragonite, High‐, Intermediate‐, and/or Low‐Mg calcite (LMC) in their skeletons. We used linear mixed statistical models to compare the effects of the pretreatments and mineralogical composition on their δ18O and δ13C values. Results Roasting was the most effective pretreatment for the removal of organic matter and light H2O2 the least, but the former had corresponding impacts on isotope ratios. δ18O values were not directly affected by wt% MgCO3, but they were significantly affected by the interaction of roasting and wt% MgCO3. This same negative effect of roasting on species with higher wt% MgCO3 occurred in δ13C values, but it was much more pronounced in δ18O values. Both H2O2 pretreatments significantly and negatively affected δ18O values at higher wt% MgCO3. Neither bleaching pretreatment significantly affected δ18O values. δ13C values were most negatively affected in skeletons with high wt% MgCO3. There was also a strong negative roasting effect and more so at higher wt% MgCO3. Bleaching and H2O2 did not significantly affect δ13C values. Conclusions Based on these results, and when using skeletal carbonate of complex mineralogies, we recommend considering the abandonment of pretreatment of biogenic carbonate for stable isotope analysis due to confounded results from previous studies, difficulties with preparation, and/or the absence of significant effects of organic material on isotope ratios. If pretreatment is necessary, avoid roasting especially at higher temperatures and durations, use minimal bleaching, and in general avoid using High‐Mg calcite species in O and C stable isotope studies. If bleaching is used, clearly indicate the concentration and duration of exposure.

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“…Effects of chemical oxidation, usually conducted using H 2 O 2, on MgCO 3 have been somewhat more investigated. Both Marr et al (2013) and Feldmeijer et al (2013) found no difference in Mg/Ca for Foraminifera treated with short periods of chemical oxidation. Barker et al (2003) however, saw reductions of up to 25% in Mg/Ca resulting from chemical cleaning, although specimens subjected to less than 20 minutes of oxidative treatment were observed to display an elevated Mg/Ca.…”

Section: Effects Of Bleaching On Compositionmentioning

confidence: 91%

The forgotten variable: Impact of cleaning on the skeletal composition of a marine invertebrate

et al. 2017

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For centuries, invertebrate collections have been subjected to various postcollection and curatorial cleaning techniques. Cleaning, however, may damage or even dissolve skeletal calcium carbonate and consequently influence any subsequent geochemical analysis. We investigated the combined effects of three cleaning variables: water (deionized and tap water), bleach (10% and 78%) and ultrasound (all for a range of durations), on the skeleton of Flustra foliacea (Linnaeus, 1758), a marine bryozoan. Treated and control carbonates were analysed both before and after cleaning, measuring: MgCO 3 in calcite (X-ray diffractometry and staining); organic:inorganic carbon ratio, using elemental analysis for total carbon by combustion and for organic carbon by acid dissolution and combustion. Treatment solutions were analysed using inductively coupled plasma atomic emission spectroscopy (ICP-AES) to detect any Ca 2+ and Mg 2+ that may have leached out.

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The effect of chemical pretreatment of sediment upon foraminiferal‐based proxies

Cited by 21 publications

References 103 publications

Boron Isotopes in Foraminifera: Systematics, Biomineralisation, and CO2 Reconstruction

Boron Isotopes in Foraminifera: Systematics, Biomineralisation, and CO2 Reconstruction

Effect of removal of organic material on stable isotope ratios in skeletal carbonate from taxonomic groups with complex mineralogies

The forgotten variable: Impact of cleaning on the skeletal composition of a marine invertebrate

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