Silicon isotopes in Antarctic sponges : an interlaboratory comparison

• Published in: Antarctic Science
• Main Authors: Hendry, Katharine R., Leng, Melanie J., Robinson, Laura F., Sloane, Hilary J., Blusztajn, Jerzy S., Rickaby, Rosalind E. M., Georg, R. Bastian, Halliday, Alex N.
• Format: Report
• Language: English
• Published: 2010
• Subjects: Biogeochemistry; Porifera; Nutrient; Calibration; Silicic acid; Antarctic; Southern Ocean; Antarc*
• Online Access: https://hdl.handle.net/1912/4380

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Cambridge University Press for personal use, not for redistribution. The definitive version was published in Antarctic Science 23 (2011): 34-42, doi:10.1017/S0954102010000593. Cycling of deep-water silicon (Si) within the Southern Ocean, and its transport into other ocean basins, may be an important player in the uptake of atmospheric carbon, and global climate. Recent work has shown that the Si isotope (denoted by δ29Si or δ30Si) composition of deep-sea sponges reflects the availability of dissolved Si during growth, and is a potential proxy for past deep and intermediate water silicic acid concentrations. As with any geochemical tool, it is essential to ensure analytical precision and accuracy, and consistency between methodologies and laboratories. Analytical bias may exist between laboratories, and sponge material may have matrix effects leading to offsets between samples and standards. Here, we report an interlaboratory evaluation of Si isotopes in Antarctic and subAntarctic sponges. We review independent methods for measuring Si isotopes in sponge spicules. Our results show that separate subsamples of non-homogenised sponges measured by three methods yield isotopic values within analytical error for over 80% of specimens. The relationship between δ29Si and δ30Si in sponges is consistent with kinetic fractionation during biomineralisation. Sponge Si isotope analyses show potential as palaeoceaongraphic archives, and we suggest Southern Ocean sponge material would form a useful additional reference standard for future spicule analyses. Cruise NBP0805 was funded by NSF Office of Polar Programs (OPP) Antarctic Sciences (grant number ANT-0636787). KH is funded by a Doherty Postdoctoral Scholarship at WHOI, and the work has also been funded by the Natural Environment Research Council (NERC) grant NE/F005296/1 and an Antarctic Science Bursary.