Preprints
https://doi.org/10.5194/bg-2020-343
https://doi.org/10.5194/bg-2020-343

  05 Nov 2020

05 Nov 2020

Review status: a revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

Calibration of Mg / Ca and Sr / Ca in coastal marine ostracods as proxy of temperature

Maximiliano Rodríguez1,2 and Christelle Not1,2 Maximiliano Rodríguez and Christelle Not
  • 1Department of Earth Sciences, Faculty of Sciences, The University of Hong Kong, Hong Kong SAR, China
  • 2The Swire Institute of Marine Science, The University of Hong Kong, Hong Kong SAR, China

Abstract. The Mg / Ca ratio of marine shells has been widely used in temperature paleoreconstructions to understand past marine conditions. Temperature calibrations are known to be species-specific but only available for a few species, despite the large number of known ostracod species. Here, we develop temperature calibrations for two shallow marine ostracods, Sinocytheridea impressa and Neomonoceratina delicata, using modern sediment samples. Our results show that adult specimens of these two species are useful as a paleothermometer. We observed significant correlations using the Mg / Ca ratios of both species to the annual (Mg / CaS. impressa = 3.7•T−62.7, Mg / CaN. delicata = 1.6•T−16.8) and April (Mg / CaS. impressa = 2.7•T−37.2, Mg / CaN. delicata = 1.6•T−15.7) temperatures. The correlation of temperature to the Mg / Ca ratio of S. impressa is more significant, and therefore should be preferred for paleoreconstructions. Re-analysis from satellite data allows us to validate our temperature calibration to an extended area around the Pearl River Estuary. Our results show that Mg / Ca of S. impressa and N. delicata ostracods can be used to reconstruct water temperature at a regional scale, which provides information on the oceanic circulation in coastal areas of the South China Seas. Finally, the Sr / Ca ratios of both species do not correlate with any of the 24 water parameters recorded by the Environmental Protection Department of Hong Kong, including temperature (21.7–24.1 °C), salinity (23.8–33.7 psu), dissolved oxygen (4.3–7.1 mg L−1), suspended solids (1.9–35.4 mg L−1) and pH (7.7–8.2).

Maximiliano Rodríguez and Christelle Not

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Maximiliano Rodríguez and Christelle Not

Maximiliano Rodríguez and Christelle Not

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Short summary
Mg / Ca in calcium carbonate shells of marine organisms such as foraminifera and ostracods has been used as a proxy to reconstruct water temperature. Here we provide new Mg / Ca-T calibrations for two shallow marine species of ostracods. We show that the water temperature in Spring produces the best calibrations, which suggests the potential use of ostracod shells to reconstruct this parameter at a seasonal scale.
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