Calcification and growth processes in planktonic foraminifera complicate the use of B/Ca and U/Ca as carbonate chemistry proxies

Salmon, K. H.; Anand, Pallavi; Sexton, Philip F; Conte, Maureen H.

doi:10.1016/j.epsl.2016.05.016

Cited by 20 publications

(21 citation statements)

References 51 publications

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“…The multiple size fraction measurements made for a given sediment trap sample indicate that both species generally yield B/Ca ratios within error, regardless of shell size (Figure ). This differs from previous studies of some dinoflagellate symbiont‐bearing foraminifera species that demonstrated that photosynthetic activity of symbionts results in poor agreement of B/Ca measurements across size fractions for a single sampling period (Babila et al, ; Salmon et al, ). This result for N .…”

Section: Resultscontrasting

confidence: 99%

“…incompta R 2 = 0.43, p = <0.025) observed in our data set differs from some previously published results for both symbiont‐bearing and symbiont‐barren species. Core top and culture results have reported positive correlations with salinity (Allen et al, , Quintana Krupinski et al, ); however, two sediment trap time series found large fluctuations in B/Ca at a site where salinity changes negligibly, suggesting a nondominant control of salinity on B/Ca (Babila et al, ; Salmon et al, ). The strongest correlation between B/Ca and salinity was reported in a global compilation of sediment trap, tow, and core top B/Ca that was supplemented with new culture results for the symbiont‐bearing species G .…”

Section: Resultsmentioning

confidence: 99%

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A Sediment Trap Evaluation of B/Ca as a Carbonate System Proxy in Asymbiotic and Nondinoflagellate Hosting Planktonic Foraminifera

Osborne

Umling

Bizimis

et al. 2020

Paleoceanog and Paleoclimatol

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The ratio of boron to calcium (B/Ca) in a subset of foraminifera has been shown to covary with seawater carbonate chemistry, making this geochemical signature a promising proxy for carbon cycle science. Some studies suggest complications with the B/Ca proxy in photosymbiont‐bearing planktonic foraminifera, while relatively few studies have investigated B/Ca in species that lack large dinoflagellate symbionts. For the first time, we use a sediment trap time series to evaluate B/Ca of subtropical and subpolar planktonic foraminifera species that are asymbiotic (Globigerina bulloides and Neogloboquadrina incompta) and a species that hosts small intrashell photosymbionts (Neogloboquadrina dutertrei). We find that B/Ca measurements across size fractions indicate overall little to no size‐dependent uptake of boron that has previously been reported in some symbiont‐bearing foraminifera. Neogloboquadrina incompta and N. dutertrei B/Ca are strongly correlated with calcite saturation, pH, and carbonate ion concentration, which is in good agreement with the limited number of published core top results. While G. bulloides B/Ca trends with seasonal fluctuations in carbonate chemistry, during discrete periods considerable B/Ca offsets occur when a cryptic G. bulloides species is known to be seasonally present within the region. We confirm presence and significant B/Ca offset between cryptic species by individual LA‐ICP‐MS analyses. This finding calls into question the use of traditional morphological classification to lump what might be genetically distinct species for geochemical analyses. Our overall results highlight the utility of G. bulloides, N. incompta, and N. dutertrei B/Ca while bringing to light new considerations regarding divergent geochemistry of cryptic species.

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Section: Resultscontrasting

confidence: 99%

Section: Resultsmentioning

confidence: 99%

A Sediment Trap Evaluation of B/Ca as a Carbonate System Proxy in Asymbiotic and Nondinoflagellate Hosting Planktonic Foraminifera

Osborne

Umling

Bizimis

et al. 2020

Paleoceanog and Paleoclimatol

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“…However, without laser ablation or electron microprobe mapping of individual shells, we cannot quantify gametogenic calcite contribution in this study. In addition, our estimates of growth rates in culture are at odds with two recent studies suggesting a rate control on planktic foraminfieral B/Ca from sediment traps [ Salmon et al , ] and from core‐top samples [ Quintana Krupinski et al , ]. Quintana Krupinski et al [] argued indirectly for a rate control, showing that that B/Ca has the strongest correlation with Ω calcite in their core‐top samples of G. bulloides and N. incompta [ Quintana Krupinski et al , ].…”

Section: Discussioncontrasting

confidence: 75%

“…However, because Ω calcite also significantly covaries with [B(OH) 4 − ]/DIC and [B(OH) 4 − ]/[HCO 3 − ], we thus cannot rule out a [B(OH) 4 − ]/DIC or a [B(OH) 4 − ]/[HCO 3 − ] control on B/Ca in their data set. Curiously, the results of Salmon et al [], who used test area density as a proxy for shell thickness (in μg/μm 2 calcite) and thus growth rate, directly conflict with the culture results of Allen et al [], who estimated average growth rates in μg d −1 . Salmon et al [] found that test area density was higher in G. ruber compared to O. universa , while Allen et al [] found the opposite trend.…”

Section: Discussionmentioning

confidence: 97%

“…Seasonal light variability has been proposed as the driver for these changes, suggesting a large influence of photosynthesis‐driven changes to pH in the foraminiferal microenvironment. Another recent sediment trap study showed that B/Ca is strongly correlated with test thickness in O. universa , G. ruber (pink), and G. truncatulinoides , linking B/Ca in planktic foraminifers to growth rate [ Salmon et al , ]. Similarly, Quintana Krupinski et al [] found that in G. bulloides and Neogloboquadrina incompta , two symbiont‐barren species, the strong covariance of B/Ca with calcite saturation (Ω calcite ) indirectly implies a growth rate control.…”

Section: Introductionmentioning

confidence: 99%

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Calibration of the B/Ca proxy in the planktic foraminifer Orbulina universa to Paleocene seawater conditions

et al. 2017

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The B/Ca ratio of planktic foraminiferal calcite, a proxy for the surface ocean carbonate system, displays large negative excursions during the Paleocene‐Eocene Thermal Maximum (PETM, 55.9 Ma), consistent with rapid ocean acidification at that time. However, the B/Ca excursion measured at the PETM exceeds a magnitude that modern pH calibrations can explain. Numerous other controls on the proxy have been suggested, including foraminiferal growth rate and the total concentration of dissolved inorganic carbon (DIC). Here we present new calibrations for B/Ca versus the combined effects of pH and DIC in the symbiont‐bearing planktic foraminifer Orbulina universa, grown in culture solutions with simulated Paleocene seawater elemental composition (high [Ca], low [Mg], and low total boron concentration ([B]T). We also investigate the isolated effects of low seawater [B]T, high [Ca], reduced symbiont photosynthetic activity, and average shell growth rate on O. universa B/Ca in order to further understand the proxy systematics and to determine other possible influences on the PETM records. We find that average shell growth rate does not appear to determine B/Ca in high calcite saturation experiments. In addition, our “Paleocene” calibration shows higher sensitivity than the modern calibration at low [B(OH)4−]/DIC. Given a large DIC pulse at the PETM, this amplification of the B/Ca response can more fully explain the PETM B/Ca excursion. However, further calibrations with other foraminifer species are needed to determine the range of foraminifer species‐specific proxy sensitivities under these conditions for quantitative reconstruction of large carbon cycle perturbations.

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An evaluation of benthic foraminiferal U/Ca and U/Mn proxies for deep ocean carbonate chemistry and redox conditions

Chen

Jin

2017

Geochem Geophys Geosyst

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The deep ocean is thought to have played a crucial role in modulating atmospheric CO2 changes, and thus reconstructions of deep ocean conditions can place important constraints on the past global carbon cycle. Some previous studies suggested that foraminiferal U/Ca could be used to infer seawater carbonate chemistry changes, but others showed complications from diagenesis and temperature. A recent downcore study suggested that foraminiferal U/Mn may be used for sedimentary redox‐conditions, but no core‐top work has been done to investigate factors affecting U/Mn. We investigate controlling factors on U/Ca and U/Mn in two benthic foraminiferal species from 120 global core‐tops and three Atlantic sediment cores. Our core‐top data reveal no significant correlation between core‐top benthic U/Ca and carbonate system parameters. The lack of an influence of deep‐water [ CO32−] on U/Ca is further supported by our downcore results. Together, our data highlight complications to use benthic U/Ca for deep‐water carbonate chemistry reconstructions. Although no correlation is found between core‐top U/Mn and hydrographic data, high‐resolution U/Mn and U/Ca in core TNO57‐21 show similar patterns to authigenic U (aU) and vary in tandem with atmospheric CO2 on millennial timescales. Changes in U/Mn, U/Ca and aU in TNO57‐21 may reflect postdepositional diagenesis linked to sedimentary oxygen, which is controlled by subantarctic surface productivity and ventilation of deep South Atlantic in the past. We suggest that benthic U/Mn and U/Ca may be used as auxiliary indicators for past sedimentary redox‐conditions and along with other proxies could reflect deep‐water oxygenation.

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Calcification and growth processes in planktonic foraminifera complicate the use of B/Ca and U/Ca as carbonate chemistry proxies

Cited by 20 publications

References 51 publications

A Sediment Trap Evaluation of B/Ca as a Carbonate System Proxy in Asymbiotic and Nondinoflagellate Hosting Planktonic Foraminifera

A Sediment Trap Evaluation of B/Ca as a Carbonate System Proxy in Asymbiotic and Nondinoflagellate Hosting Planktonic Foraminifera

Calibration of the B/Ca proxy in the planktic foraminifer Orbulina universa to Paleocene seawater conditions

An evaluation of benthic foraminiferal U/Ca and U/Mn proxies for deep ocean carbonate chemistry and redox conditions

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