Salinity effects on the Mg/Ca and Sr/Ca in starfish skeletons and the echinoderm relevance for paleoenvironmental reconstructions
- 1Laboratoire de Biologie Marine (CP 160/15), Université Libre de Bruxelles, 50 avenue F.D. Roosevelt, B-1050 Brussels, Belgium
- 2Département des Invertébrés, Institut Royal des Sciences Naturelles de Belgique, 29 rue Vautier, B-1000 Brussels, Belgium
- 3Section de Minéralogie, Pétrographie et Géochimie, Musée Royal d'Afrique Centrale, 13 Leuvensesteenweg, B-3080 Tervuren, Belgium
- *E-mail: phdubois{at}ulb.ac.be.
Abstract
Skeletal Mg/Ca ratios of well-preserved fossil echinoderms have been used to reconstruct past Mg/Ca ratio in seawater up to the Phanerozoic, taking into account the known temperature effect on this ratio. This study investigates the effects of salinity and growth rate on Mg/Ca and Sr/Ca ratios in starfish calcite skeletons grown in experimental conditions. Both ratios are not related to growth rate: on the contrary, both are positively related to salinity. This effect induces an error on the reconstructed Mg/Ca ratio in seawater that may reach 46%. An intriguing inverse relation between skeletal Sr/Ca ratio and temperature was recorded. The salinity effects are presumably due to physiological regulation processes.
Footnotes
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↵GSA Data Repository item 2009087, materials and methods details, Table DR1 (salinity and temperature conditions), Table DR2 (data presented in Figure 1), Figure DR1 (schematic cross section of Asterias rubens arm), and Figure DR2 (Sr/Ca versus size relationship), is available online at www.geosociety.org/pubs/ft2009.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA.
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- Received 6 August 2008.
- Revision received 26 November 2008.
- Accepted 1 December 2008.
- © 2009 Geological Society of America
