The Mg/Ca of marine calcareous Planktic Foraminifera (PF) shells is commonly used for sea surface temperature reconstructions. However, compared to open marine environments, hypersaline (>40) oligotrophic seas have been shown to accommodate PF with higher Mg/Ca and divergent temperature to Mg/Ca relationships. To investigate influencing factors of PF Mg uptake in hypersaline regions, we measured the Mg/Ca of two flux-dominating PF species, Globigerinoides ruber albus and Turborotalita clarkei, derived from a monthly resolved time series of sediment traps in the Gulf of Aqaba, northern Red Sea as well as the corresponding temperature, salinity, and pH values. The PF exhibit elevated Mg/Ca which cannot be explained by post-deposition or interstitial sediment diagenetic processes. G. ruber albus displays Mg/Ca trends that strongly follow seasonal mixed layer temperature changes. Conversely, T. clarkei Mg/Ca trends do not follow temperature but rather show significant Mg/Ca enrichment following mixing of the surface water column. We present a framework for incorporating elevated Mg/Ca into global Mg/Ca-T calibrations for G. ruber albus and present a new Mg/Ca-T calibration suitable for hypersaline marine environments.
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We wish to acknowledge B. Yarden and the IUI marine crew for their assistance in field work and sample handling. The National Monitoring Program is thanked for their support and sharing results and E. Levy for comments and suggestions. We are thankful for reviews by Yair Rosenthal, Lennart de Nooijer and another anonymous reviewer, which significantly improved this manuscript. This work was supported by Israel Science Foundation Grant 834/19 (to AT), a Minerva PhD Fellowship stipend (to NL) and a scholarship from the Advance School for Environmental Studies, HUJI (to NL). Open Access funding enabled and organized by Projekt DEAL.
© 2023 The Authors. Geochemistry, Geophysics, Geosystems published by Wiley Periodicals LLC on behalf of American Geophysical Union.