Mg and Sr uptake in benthic foraminifera Ammonia aomoriensis based on culture and field studies
2019
Yu, Zhoufei | Lei, Yanli | Li, Tiegang | Zhang, Shuai | Xiong, Zhifang
Trace elements incorporated in foraminiferal test are commonly used as paleoproxies, however, the incorporation of trace elements is controlled by more than one environmental parameter. We conducted one year sampling from June 2014 to May 2015 in the Qingdao intertidal flat, the Yellow Sea, and retrieved surface samples in the Jiaozhou Bay (3.9–6.8 m water depth), the Yellow Sea in February 2015, as well as performed a laboratory culture experiment under temperature 6–24 °C and salinity 24–33 psu, by combining δ18Oc values of field A. aomoriensis, parameters controlling Mg/Ca and Sr/Ca ratios of Ammonia aomoriensis were investigated. Under constant seawater chemistry, temperature dominates the magnesium incorporation into A. aomoriensis test by an exponential increase of 5.1% per °C (Mg/Ca = 1.0980 (±0.2073) e0.0510 (±0.0097) T; Mg/Ca = 0.5565 (±0.3897) + 0.1279 (±0.0242) T, 2.4–24 °C including field samples). Whereas, temperature has no significant effect on Strontium uptake. Calcite Sr/Ca of A. aomoriensis is primarily explained by Mg/Ca value (~3% per mmol/mol). Salinity variations are of subordinate importance for both Mg and Sr content in the test of A. aomoriensis, Mg/Ca raises linearly with approximately 2% per salinity unit, and Sr/Ca increases ~1% per salinity unit. Importantly, biological mechanism might be an inestimable factor perturbing Mg and Sr response to environmental parameters in natural waters, complicating the paleoclimate reconstruction.
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