|Dataset:||Isotopes delta-11B, delta-13C and delta-18O in deep-sea bamboo corals Keratoisis (Bamboo Coral Boron Isotopes project)|
|Project(s):||Calibration and application of the boron isotope seawater-pH indicator in deep-water corals (Bamboo Coral Boron Isotopes)|
|Description:||Keratoisis δ11B, δ13C and δ18O |
δ11B, δ13C and δ18O in deep-sea bamboo corals
References to detailed boron isotope methodology:
Penman D. E., Hönisch B., Rasbury E. T., Hemming N. G. and Spero H. J. (2013) Boron, carbon, and oxygen isotopic composition of brachiopod shells: Intra-shell variability, controls, and potential as a paleo-pH recorder. Chem. Geol. 340, 32-39.
|Acquisition Description:|| |
Sampling and Analytical Methodology:
For boron isotope analyses, 1 to 2 mg of calcite powder was cleaned of organic material with 1% H2O2 buffered in 0.1N NaOH at 80°C for twenty minutes, then rinsed five times with boron-free MilliQ water under ultrasonication. Recovery varied from 70 to 90%, as fine-grained material was invariably lost to suspension during rinse steps. Cleaned coral powders were dissolved in 2N HCl immediately prior to analysis; Fisher Optima® grade chemicals were used for all treatments. A sufficient volume of analyte to obtain a minimum of 1 ng of B (typically 1.5 to 2 µL depending on sample B concentration) was loaded with 1.0 µL of a boron-free seawater matrix solution onto degassed rhenium filaments.
Boron isotope ratios were measured on a Thermo TRITON multicollector thermal ionization mass spectrometer at LDEO in negative-ion mode (NTIMS, see detailed methodology in Foster et al., 2013). Average electric potentials for 11BO2- ranged between 120 and 300 mV. Boron isotope ratios are reported in delta notation (δ11B) relative to the NIST 951 boric acid standard reference material. Mass 26 (12C14N-) was monitored immediately prior to analyses, to check for isobaric interference on 10BO2- from organic material. No samples were excluded based on this criterion, as mass 26 counts were below previously determined thresholds for organic matter contamination (Foster et al., 2013). Boron concentrations were determined in a representative sample for each coral by isotope dilution with 5 ppm NIST 952 boric acid reference material. A minimum of three acceptable repeat analyses was required for each reported δ11B value, where analyses with >1‰ within-run fractionation were discarded. Although only two acceptable repeat analyses were obtained for five samples, these numbers are reported here because of their close correspondence with surrounding measurements (italicized δ11B values in dataset).
Uncertainty in δ11B measurements is reported as the larger value of either twice the measurement standard error (2se=2σ/√n, where n is the number of repeat analyses on a single sample solution), or the external error, which is given as the 2se on repeat analyses of an in-house standard of NIST 951 precipitated in vaterite (see Foster et al., 2013 and Penman et al., 2013).
|Processing Description:|| |
BCO-DMO Processing Notes
Calibration and application of the boron isotope seawater-pH indicator in deep-water corals
Description from NSF award abstract: Anthropogenic CO2 enters the ocean in the high latitudes, from where it spreads into the deep ocean interior. Because carbonate ion saturation at greater water depth is generally reduced in the deep ocean, deep-sea corals may be particularly vulnerable to ocean acidification. Efforts are needed to determine the effects of changing seawater chemistry on these ecosystems, and in particular reconstructions of past pH-variations experienced by these corals may help to implement long-term management plans for deep-sea coral reefs. This project will provide new insight into the effect of changing seawater carbonate chemistry and anthropogenic ocean acidification on deep-sea coral reefs. The researchers will calibrate the boron isotope and B/Ca paleo-pH proxies in several species of modern and cultured deep-sea corals. The resulting proxy calibrations will be used to interpret the boron isotope composition of live collected and fossil deep-sea corals with regard to past ocean pH changes. Live collected corals from the North Atlantic and Southern Ocean will provide ultra-high resolution temporal records of anthropogenic CO2 invasion at intermediate depths. Radiometrically dated corals from the same locations will be used to document pH changes in the deep ocean over the last deglaciation. Comparison of paleo-pH with already established changes in coral species composition will allow interpretation of coral sensitivity to ocean acidification. The project will also improve paleo-pH reconstructions by cross- calibrating the principal techniques of boron isotope analysis. Related Reference:Hoenisch_ocean_acidification_2010
Deployment description for shoreside BAMBOO CORAL BambooCoral_Hoenisch
Locations for studied bamboo corals
|Instrument||IR Mass Spec - Thermo Delta V+|
|Description||Samples were analyzed on a Thermo Delta V+ with dual inlet and Kiel IV device at the Lamont-Doherty Earth Observatory (LDEO)|
|Generic Instrument Name||Isotope-ratio Mass Spectrometer|
|Generic Instrument Description||The Isotope-ratio Mass Spectrometer is a particular type of mass spectrometer used to measure the relative abundance of isotopes in a given sample (e.g. VG Prism II Isotope Ratio Mass-Spectrometer).|
|Instrument||TI Mass Spec - Thermo TRITON multicollector thermal ionization mass spectrometer|
|Description||Boron isotope ratios were measured on a Thermo TRITON multicollector thermal ionization mass spectrometer at LDEO in negative-ion mode (NTIMS, see detailed methodology in Foster et al., 2013)|
|Generic Instrument Name||Thermal Ionization Mass Spectrometer|
|Generic Instrument Description||A Thermal Ionization Mass Spectrometer (TIMS) is an instrument that measures isotopic ratios after electrical excitation of a sample causes ionization of the isotopes.|