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Silicon isotope and silicic acid uptake in surface waters of Marguerite Bay, West Antarctic Peninsula

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)143-150
Number of pages8
JournalDeep Sea Research Part II: Topical Studies in Oceanography
Volume139
Early online date2 Nov 2016
DOIs
DateAccepted/In press - 20 Oct 2016
DateE-pub ahead of print - 2 Nov 2016
DatePublished (current) - May 2017

Abstract

The silicon isotope composition (δ30Si) of dissolved silicon (DSi) and biogenic silica (BSi) provides information about the silicon cycle and its role in oceanic carbon uptake in the modern ocean and in the past. However, there are still questions outstanding regarding the impact of processes such as oceanic mixing, export and dissolution on the isotopic signature of seawater, and the impacts on sedimentary BSi. This study reports the δ30Si of DSi from surface waters at the Rothera Time Series (RaTS) site, Ryder Bay, in a coastal region of the West Antarctic Peninsula (WAP). The samples were collected at the end of austral spring through the end of austral summer/beginning of autumn over two field seasons, 2004/5 and 2005/6. Broadly, for both field seasons, DSi diminished and δ30Si of DSi increased through the summer, but this was accomplished during only a few short periods of net nutrient drawdown. During these periods, the δ30Si of DSi was negatively correlated with DSi concentrations. The Si isotope fractionation factor determined for the net nutrient drawdown periods, ɛuptake, was in the range of -2.26 to -1.80 ‰ when calculated using an open system model and -1.93 to -1.33 ‰ when using a closed system model. These estimates of ɛ are somewhat higher than previous studies that relied on snapshots in time rather than following changes in δ30Si and DSi over time, which therefore were more likely to include the effects of mixing of dissolved silicon up into the mixed layer. Results highlight also that, even at the same station and within a single growing season, the apparent fractionation factor may exhibit significant temporal variability because of changes in the extent of biological removal of DSi, nutrient source, siliceous species, and mixing events.
Paleoceanographic studies using silicon isotopes need careful consideration in the light of our new results.

    Research areas

  • Silicon, Isotopes, Fractionation, Time series, Ryder Bay , Southern Ocean

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    Rights statement: This is the author accepted manuscript (AAM). The final published version (version of record) is available online via Elsevier at http://www.sciencedirect.com/science/article/pii/S0967064516303216. Please refer to any applicable terms of use of the publisher.

    Accepted author manuscript, 832 KB, PDF document

    Licence: CC BY-NC-ND

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