, Volume 517, Issue 1, pp 1-13

First online:

On the celestite-secreting Acantharia and their effect on seawater strontium to calcium ratios

  • Patrick De DeckkerAffiliated withDepartment of Earth and Marine Sciences, The Australian National University

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Significant variations in the Sr/Ca in waters from the eastern Indian Ocean in the vicinity of Australia, both from the surface and from shallow depth profiles, are documented. The strontium sulfate-secreting protozoans Acantharia, which are common in the upper 400 m of the oceans, especially at low latitudes, contribute substantially to changes in the Sr/Ca of oceanic waters by extracting Sr for the formation of their skeletons. Below such depths, these organisms dissolve and the Sr/Ca of seawater regains its ‘conservative’ nature. This mechanism accounts for some of the variability of the Sr/Ca near the surface of the ocean, but this may still be found at depth as surface waters become entrained at greater depths. It is argued here that the noted Sr/Ca variations may explain discrepancies between coral data sets from different parts of the oceans, and calls for caution when reconstructing sea-surface temperatures from the Sr/Ca of corals.

Acantharia sarcodine protozoan strontium sulfate Indian Ocean coral palaeothermometry seawater chemistry