Foraminifera phosphatization

The similarity between cadmium profiles and nutrient profiles has been used as a means of reconstructing past patterns of primary production and nutrient cychng. Several attempts have been made to reconstruct phosphate concentrations from the Cd Ca ratio of foraminifera (Boyle, 1988 Elderfield and Rickaby, 2000). Foraminifera substitute Cd for Ca in the lattice of their calcite tests, and the ratio of Cd Ca incorporation varies with the Cd Ca ratio of seawater (Boyle,... 

Measuring the carbon isotope ratio in the calcite tests of bottom dwelling (benthic) foraminifera is perhaps the most widespread method for reconstructing the distribution and properties of deepwater masses. The carbon isotope ratios in the foraminifera reflect that ratio in seawater. In turn, the carbon isotope ratio in the deep sea is primarily controlled by the regeneration of C-poor organic material and has a distribution much like a nutrient such as phosphate in the modern ocean. While a... 

In order to estimate paleoceanographic nutrient levels, and thereby explore links between nutrient variability, atmospheric CO2 and climate change, a range of nutrient proxies have been developed. The ratio of cadmium (Cd) to calcium (Ca) in benthic foraminifera has been used as a proxy for dissolved phosphate, based on the observation that dissolved cadmium and phosphate concentrations are linearly correlated in modern oceanic waters (Boyle, 1988). While the basis of the Cd PO4 relationship is not understood, from either a biochemical or geochemical standpoint (e.g., Cullen et al., 2003),... 

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