Automated cleaning of foraminifera shells before Mg/Ca analysis using a pipette robot

The long‐chain diol index (LDI) is a relatively new proxy for sea surface temperature (SST) which has been rarely applied in upwelling regions. Here, we evaluated its application by comparison with other SST records obtained by commonly used proxies, that is, the Mg/Ca ratio of the planktonic foraminifera species Globigerinoides ruber and the alkenone paleothermometer UK´37. We focused on the last glacial–interglacial transition of four different sedimentary archives from the western and northern Arabian Sea, which are currently under the influence of monsoon‐induced upwelling and the associated development of an oxygen minimum zone. The normalUK′37 ${{\mathrm{U}}^{\mathrm{K}\prime }}_{37}$ and Mg/CaG.ruber SST records revealed an increase of 0.6–3.4°C from the Last Glacial Maximum to the late Holocene with somewhat higher amplitude in the northern part of the Arabian Sea than compared to the western part. In contrast, the LDI SSTs did not reveal major changes during the last glacial–interglacial transition which was followed by a decreasing trend during the Holocene. The LGM versus the Holocene LDI SSTs ranged between −0.2 and −2.7°C. Particularly at one record, offshore Oman, the SST decrease during the Holocene was high in amplitude, suggesting a potential cold bias, possibly related to changes in upwelling intensity. This indicates that care has to be taken when applying the LDI for annual mean SST reconstruction in upwelling regions.

Section: Globigerinoides Ruber δ 18 O and Mg/ca Analysis Of Core Pasom3mentioning

confidence: 68%

“…Additional quality control for potential contamination was done through molar ratios of Fe, Mn, Al, and Ca (mmol/mol) following Johnstone et al. (2016) and Lear et al. (2015).…”

Section: Methodsmentioning

confidence: 99%

Applicability of the Long Chain Diol Index (LDI) as a Sea Surface Temperature Proxy in the Arabian Sea

Erdem

Lattaud

Erk

et al. 2021

“…Sample recovery, where measured (n ¼ 105), was on average of 24% (1σ ¼ 14%). This is less than for samples containing multiple tests, where recovery is around 50% (Johnstone et al, 2016), and can probably be at least partly explained by there being a fixed loss due to surface tension. There was moderate correlation between initial test mass and sample recovery (r ¼ 0.45, p < 0.001, n ¼ 97) (Figure 2a).…”

Section: Quality Control Of Automated Cleaningmentioning

confidence: 79%

“…Here single tests are cleaned according to conventional cleaning protocols which involve rinsing and ultrasonication of samples (Marchitto, 2006). We use an automated method of cleaning foraminifera samples (Johnstone et al, 2016), which is designed to carry out the cleaning protocol of Barker et al (2003), with modifications to optimize the method for small samples.…”

Section: Assessment Of Automated Cleaning Of Single Testsmentioning

confidence: 99%

“…The step of removing noncarbonate grains using a fine brush was omitted. The pipette-robot protocol was based on that of Johnstone et al (2016), modified slightly for single test samples, as follows. Well plates for the cleaning procedure were Framestar Conical 96-well plates with a maximum well volume of 205 μl; reagent volumes were 80 μl for water and methanol and 60 μl for buffered H 2 O 2 ; the final acid leaching step was omitted.…”

Section: Sample Preparation and Analysis 251 Cleaning Of Individuamentioning

confidence: 99%

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Single Tests of Thermocline Dwelling Foraminifera Globorotalia inflata as Recorder of Upper Water Column Structure off Mauritania (NW Africa): Methodology and Paleoceanographic Use

Johnstone

Kuhnert

Bickert

et al. 2020

Self Cite

Thermocline‐dwelling foraminifera calcify over a depth range of several hundred meters; analysis of individual shells therefore allows insight to the hydrography of the upper water column. We analyzed δ18O, δ13C, and Mg/Ca of individual tests of the planktonic foraminifera Globorotalia inflata from a sediment core (GeoB7926‐2) obtained from 20°N in the eastern tropical Atlantic. To facilitate sample throughput, tests were cleaned before Mg/Ca analysis using a pipette robot. The eight samples came from five time periods with contrasting climate states. Median reconstructed temperatures were lowest during the warmth of the Bølling Allerød BA) (11.8°C), while highest temperatures (>14°C) were recorded during the cold periods of the Last Glacial Maximum (LGM), late Heinrich Stadial 1 (HS1), and the Younger Dryas (YD). Southward shift in the subtropical gyre during Northern Hemisphere cold periods and modulation by upwelling could explain the temperature change but not all of the salinity change. δ18Oseawater‐IVC indicated that salinity was higher than the global average during the LGM, with very high salinity excursions in HS1 and a smaller excursion in the YD. The upwelling signature was most strongly imprinted on range in δ13C. The large changes in salinity and δ13C between time slices cannot be explained by upwelling intensity but indicate the presence of a very saline water mass, with low δ13C, in the eastern North Atlantic subsurface during Northern Hemisphere cold periods.

Increased Productivity in the Equatorial Pacific During the Deglaciation Inferred From the Ba/Ca Ratios of Non‐Spinose Planktic Foraminifera

Fritz-Endres

Fehrenbacher

Russell

et al. 2022

Records of export production (EP) from the surface ocean link primary productivity to burial and provide critical information about the strength of the biological pump and its relationship to carbon storage over climate transitions (see Sigman & Boyle, 2000 and references therein). However, changes in productivity over glacial-deglacial transitions are not yet well constrained (Carter et al., 2020;Loubere, 1999). Previous studies in the equatorial Pacific have alternately stated that productivity was greater during glacial periods (Herguera