A reappraisal of the vital effect in cultured benthic foraminifer Bulimina marginata on Mg/Ca values: assessing temperature uncertainty relationships

[摘要] The reconstruction of past temperatures is often achieved through measuringthe Mg/Ca value of foraminiferal test carbonate. The diversity inforaminiferal Mg/Ca–temperature calibrations suggests that there is also abiological control on this proxy. This study presents a newMg/Ca–temperature calibration for the benthic foraminifer Bulimina marginata, based oncultures under a range of temperatures (4–14 °C). Measured Mg/Ca valuesfor B. marginata correlate with temperature (Mg/Ca = (1.10 ± 0.10) e^{(0.045±0.009)T}, R² = 0.28 p < 0.01). The inter-individual variability is,however, also significant (standard deviation is 10–35% of the average).Before applying this or any calibration, the effect of the inter-individualvariability on the accuracy of the Mg/Ca–temperature calibration has to beevaluated. The inter-individual variability is quantified and split into threecomponents, namely (1) an analytical error, (2) an environmental effect and (3)a vital effect. The effect of inter-individual variability on the accuracyof Mg/Ca–temperature calibrations depends on the sensitivity of thecalibration used and the number of individuals measured (temperatureuncertainty = (0.33 · N^−0.50)/sensitivity). The less sensitive acalibration, the greater is the impact of inter-individual variability,which can partly be circumvented by measuring more individuals. This studyshows the link between inter-individual variability and sensitivity andquantifies their influence on the accuracy of Mg/Ca–temperaturecalibrations. Differences in the sensitivity of the Mg/Ca–temperaturecalibration of foraminifera may depend on the environmental conditions inwhich foraminifera live and their concurring ecological strategies.

[学科分类] 地球化学与岩石