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Effects of growth and dissolution on the fractionation of silicon isotopes by estuarine diatoms
Stockholm University, Faculty of Science, Department of Geological Sciences.
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2014 (English)In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 0016-1258, Vol. 130, 156-166 p.Article in journal (Refereed) Published
Abstract [en]

Studies of silicon (Si) isotope fractionation during diatom growth in open ocean systems have documented lower Si isotopic values (delta Si-30) in the biogenic silica of diatom frustules compared to dissolved silicon. Recent findings also indicate that Si isotope fractionation occurs during dissolution of diatom frustules, producing higher delta Si-30 values in the remaining biogenic silica. This study focuses on diatoms from high production areas in estuarine and coastal areas that represent approximately 30-50% of the global marine primary production. Two species of diatoms, Thalassiosira baltica and Skeletonema marinoi, were isolated from the brackish Baltic Sea, one of the largest estuarine systems in the world. These species were used for laboratory investigations of Si isotope fractionation during diatom growth and the subsequent dissolution of the diatom frustules. Both species of diatoms give an identical Si isotope fractionation factor during growth of -1.50 +/- 0.36 parts per thousand (2 sigma) for Si-30, which falls in the range of -2.09 parts per thousand to -0.55 parts per thousand of published data. Our results also suggest a dissolution-induced Si isotope fractionation factor of -0.86 parts per thousand at early stage of dissolution, but this effect was observed only in DSi and no significant Si isotope change was observed for BSi. The growth and dissolution results are applied to a Baltic Sea sediment core to reconstruct DSi utilization by diatoms, and found to be in agreement with the observed DSi uptake rates in the overlying water column during diatom growth.

Place, publisher, year, edition, pages
2014. Vol. 130, 156-166 p.
National Category
Geophysics Geochemistry
URN: urn:nbn:se:su:diva-102456DOI: 10.1016/j.gca.2014.01.024ISI: 000332405700011OAI: diva2:710827
FormasSwedish Research Council, VR-2007-4763


Available from: 2014-04-08 Created: 2014-04-07 Last updated: 2014-09-10Bibliographically approved

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Humborg, ChristophMörth, Carl-Magnus
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Department of Geological SciencesDepartment of Applied Environmental Science (ITM)Baltic Nest Institute
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