Boron Contamination during Boron Isotope Analysis of Planktonic Foraminifera

Abstract. So-called "vital effects" are a collective term for a suite of physiologically and metabolically induced variability in oxygen (δ18O) and carbon (δ13C) isotope ratios of planktonic foraminifer shells that hamper precise quantitative reconstruction of past ocean parameters. Correction for potential isotopic offsets from equilibrium or the expected value is paramount, as too is the ability to define a comparable life stage for each species that allows for direct comparison. Past research has focused upon finding a specific size range for individual species in lieu of other identifiable features, thus allowing ocean parameters from a particular constant (i.e. a specific depth or season) to be reconstructed. Single-shell isotope analysis of fossil shells from a mid-latitude North Atlantic Ocean piston core covering Termination III (200 to 250 ka) highlight the advantage of using a dynamic size range, i.e. utilising measurements from multiple narrow sieve size fractions spanning a large range of total body sizes, in studies of palaeoclimate. Using this methodology, we show that isotopic offsets between specimens in successive size fractions of Globorotalia inflata and Globorotalia truncatulinoides are not constant over time, contrary to previous findings. For δ18O in smaller-sized globorotalids (212–250 μm) it is suggested that the offset from other size fractions may reflect a shallower habitat in an early ontogenetic stage. A reduction in the difference between small and large specimens of G. inflata between insolation minima and maxima is interpreted to relate to a prolonged period of reduced water column stratification. For the shallow-dwelling species Globigerina bulloides, no size–isotope difference between size fractions is observed, and the variability in the oxygen isotopic values is shown to correlate well with the seasonal insolation patterns. As such, patterns in oxygen isotope variability of fossil populations may be used to reconstruct past seasonality changes.

Download Full-text

Boron isotope analysis of coral skeletons by laser ablation MC-ICP-MS: new insights into calcification and environmental reconstruction at high temporal resolution

10.5194/egusphere-egu2020-8202 ◽

2020 ◽

Author(s):

Gavin L. Foster ◽

Thomas B. Chalk ◽

Christopher D. Standish

Keyword(s):

Laser Ablation ◽

Trace Element ◽

Temporal Resolution ◽

Isotope Analysis ◽

Coral Skeleton ◽

Boron Isotope ◽

High Temporal Resolution ◽

Carbonate System ◽

Seawater Ph ◽

Icp Ms

Despite being some of the largest bio-constructions on the planet, coral reefs are made by many millions of cm- to mm-sized polyps of Scleractinian corals. Calcification occurs in a micron sized space sandwiched between the coral animal and the existing skeleton, known as the extra cellular medium (ECM). The coral animal has a tight control on the carbonate system in this space through deploying enzymatic pumps (e.g. Ca-ATPase) and secreting acidic-rich proteins. Tracking the state of the carbonate system in the ECM is therefore key to forming a mechanistic understanding of how environmental change, such as ocean acidification, influences skeletal formation and ultimately the growth and resilience of these important ecosystems.Traditional means to examine ECM composition is through the use of micro-electrodes. While these approaches have revealed many key insights they are, by their nature, invasive.&#160; They also only provide snap shots of information for corals grown in the laboratory. The boron isotopic composition of the coral skeleton and its boron content (expressed as B/Ca ratio) have recently emerged as a viable alternative approach to fully characterise the carbonate system in the ECM.&#160; However, most studies employ bulk sampling techniques which require averaging across both structural elements of the coral skeleton and many months to years of growth. Laser ablation MC-ICP-MS approaches are now available as an alternative sampling protocol (e.g. Standish et al. 2019), and along with B/Ca (and other trace element) measurements this not only allows a reconstruction of the full carbonate system of the ECM from an analysis of the skeleton of any coral (cultured or wild) at unprecedented spatial and temporal resolution, but it also allows an examination of the influence of the carbonate system in the ECM on trace element incorporation.&#160;Here we present boron isotope and trace element analyses of several tropical, reef-building, corals to examine the nature and magnitude of fine scale variation in ECM composition.&#160; By studying corals from locations where external seawater is well known we also gain insights into trace element incorporation and whether external seawater pH can be accurately reconstructed from the boron-based proxies at weekly (or better) resolution.&#160;&#160;Standish, C.D., Chalk, T.B., Babila, T.L., Milton, J.A., Palmer, M.R., Foster, G.L. (2019) The effect of matrix interferences in situ boron isotope analysis by laser ablation MC-ICP-MS, Rapid Communications in Mass Spectrometry 33: 959&#8211;968 https://doi.org/10.1002/rcm.8432

Download Full-text

Estimating Paleogene atmospheric pCO2using boron isotope analysis of foraminifera

GFF ◽

10.1080/11035890001221127 ◽

2000 ◽

Vol 122 (1) ◽

pp. 127-128 ◽

Cited By ~ 3

Author(s):

Paul N. Pearson ◽

Martin R. Palmer

Keyword(s):

Isotope Analysis ◽

Boron Isotope

Download Full-text

Late Pleistocene Glacial–Interglacial related shell size isotope variability in planktonic foraminifera as a function of local hydrology

Biogeosciences Discussions ◽

10.5194/bgd-12-135-2015 ◽

2015 ◽

Vol 12 (1) ◽

pp. 135-189 ◽

Cited By ~ 1

Author(s):

B. Metcalfe ◽

W. Feldmeijer ◽

M. de Vringer-Picon ◽

G.-J. A. Brummer ◽

F. J. C. Peeters ◽

...

Keyword(s):

Size Range ◽

North Atlantic Ocean ◽

Life Stage ◽

Planktonic Foraminifera ◽

Isotope Analysis ◽

Past Research ◽

Individual Species ◽

Shell Size ◽

Size Fractions ◽

Water Column Stratification

Abstract. So called "vital effects", a collective noun for a suite of physiological and metabolic induced variability, in oxygen (δ18O) and carbon (δ13C) isotope ratios of planktonic foraminifer shells hamper precise quantitative reconstruction of past ocean parameters. Correction for potential isotopic offsets from the equilibrium or the expected value is paramount, as too is the ability to define a comparable life-stage for each species that allows for direct comparison. Past research has focused upon finding a specific size range for individual species in lieu of other identifiable features, that allow ocean parameters from a particular constant (i.e. a specific depth or season) to be reconstructed. Single shell isotope analysis of fossil shells from a mid-latitude North Atlantic Ocean piston-core covering Termination III (200 to 250 kyr) highlight the advantage of using a dynamic size range in studies of palaeoclimate. Using this methodology, we show that isotopic offsets between specimens in successive size fractions of G. inflata and G. truncatulinoides are not constant over time, contrary to previous findings. For δ18O in smaller sized globorotalids it is suggested that the offset from other size fractions may reflect a shallower habitat in an early ontogenetic stage. A reduction in the difference between small and large specimens of G. inflata between insolation minima and maxima is interpreted to relate to a prolonged period of reduced water column stratification. For the shallow dwelling species G. bulloides no size isotope difference between size fractions is observed, and the variability in the oxygen isotopic values are shown to correlate well with the seasonal insolation patterns. As such, patterns in oxygen isotope variability of fossil populations may be used successfully for reconstruction of past seasonality changes.

Download Full-text